US3813936A - Methods and apparatus for testing earth formations - Google Patents

Abstract

In the representative embodiments of the new and improved methods and apparatus for testing earth formations disclosed herein, fluid-admitting means are placed into sealing engagement with a potentially-producible earth formation and selectivelyoperable valve means on the fluid-admitting means are opened to place a filtering medium situated between the fluid-admitting means and a flow line in communication with the isolated formation. Then, before testing is commenced, well bore fluids are introduced into the flow line and discharged through the filtering medium in a reverse direction and into the earth formation for cleaning the filtering medium of potentiallyplugging materials before connate fluids are introduced into the fluid-admitting means.

Description

Urbanosk et a .Bnne d, WM

[ METHODS AND APPARATUS FOR TESTiNG 3,577,731 5/1971 Lebourg 73/152 3,653,436 4/1972 Whitten l66/l00 EARTH FORMATHONS William R. Sherman; Stewart F. Moore in the representative embodiments of the new and improved methods and apparatus for testing earth formations disclosed herein, fluid-admitting means are placed into sealing engagement with a potentiallyproducible earth formation and selectively-operable valve means on the fluid-admitting means are opened to place ,a filtering medium situated between the fluidadmitting mfins and a flow line in communication with the isolated formation. Then, before testing is commenced, well bore fluids are introduced into the flow line and discharged through the filtering medium in a reverse direction and into the earth formation for cleaning the filtering medium of potentially-plugging materials before connate fluids are introduced into the fluid-admitting means.

[75] Inventors: Harold J. Urhanoslty, Pearland;

Frank R. Whitten, Houston, both of Tex.

[73] Assignee: Schlumberger Technolog Corporation, New York, NY. [22-] Filed: Dec. 8, 1972 [2]] Appl. No.: 313,225

[52] U8. Cl. 73/l55, 73/421 R [51] Int. Cl EZlh dQ/tlh [58] Field of Search 73/155, 421 R, 151, 152; '166/100 [56] References Cited UNITED STATES PATENTS 3,0] l,554 l2/l 96l Desbrandes et al. l66/l00 3.254.531 6/1966 Briggs..lr..... 3.352,36l ll/l967. Urbanosky 3,530,933 9/l97() Whitten l66/lOO' 3.565,l69 2/l97l Bell l66/l00 PAEENEEM an POWER SUPPLY i METHODS AND ArrAnATus son "merino even should it be quickly realized that a particular sampling or testing operation already underway will probably be unsuccessful, the operator has no choice except to discontinue the operation and then return the tool to the surface. This obviously results in a needless loss of time and expense which would usually be avoided if another attempt could be made without having to remove the tool from the well bore.

One of the most significant problems which have heretofore prevented the production of a commercially successful repetitively-operable formation-testing tool has been in providing a suitable arrangement for reliably establishing fluid or pressure communication with imcompetent or unconsolidated earth formations. Although the several new and improved testing tools respectively shown in U.S. Pat. No. 3,352,361, U.S. Pat, No. 3,530,933, U.S. Pat. No. 3,565,169 and U.S. Pat. No. 3,653,436 are especially arranged for testing unconsolidated formations, for one reason or another these tools are not adapted for performing more than one testing operation during a single run in a given well bore. For example, as described in these patents, each of these new and improved testing tools employs a tubular sampling member which is cooperatively associated with a filtering medium for preventing the unwanted entrance of unconsolidated formation materials into the testing tool. Experience has shown, however, that although these new and improved filtering arrangements are highly successful for a single operation, subsequent tests cannot be reliably performed since particles of mudcake and exceptionally-fine formation materials will often coat or plug the filtering medium.

Thus, following each test, the testing tool must be reattained in the practice of the new and improved methods described herein by placing normally-closed fluidadmitting means having filtering means cooperatively arranged therewith into sealing engagement with an earth formation, opening communication between the filtering means and the earth formation, and discharging well bore fluids in a reverse direction through the filtering medium and into the formation for cleansing the filtering medium of unwanted possibly-plung matter such as mudcake and loose formation materials.

To further achieve the obiects of the prwent invention, formationtesting apparatus is provided with fiuidadmitting means pted to be seaiingiy engaged with a potentialiyproducible earth formation. To limit the entrance of loose formation materials into the fluidadmitting means, filtering means are disposed in the fluid-admitting means. Normaliy-closed valve means are cooperatively arranged in the fluid-admitting means for seiective movement to an open position for opening communication between an isolated earth formation and the filtering means. Means are further provided for discharging well bore fluids in i3 reverse direction through the filtering means upon opening of the valve means for flushing possibly-plugging materials away from the filtering means.

The novel features of the present invention are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may be best understood by way of the following description of exemplary apparatus employing the principles of the invention as illustrated in the accompanying drawings, in which:

H0. 1 depicts the surface and downhole portions of a preferred embodiment of new and improved formadon-testing apparatus for practicing the invention and incorporating its principles;

FiGS. 2A and 28 together show a somewhatschematic representation of the formation-testing tool illustrated in FIG. 1 as the tool will appear in its initiai operating position; and v FIGS. 3-5 A and B respe'ctively'depict the successive positions of various componentsjof the new and improved tool shown in FIGS. 2A and 28 during the course of a typical testing and sampling operation. Turning now to FIG. i, a preferred embodiment of a new and improved sampling and measuring too! it? incorporating the principles of the present invention is shown as it will appear during the course of a typical measuring and sampling operation in a well bore such as a borehole i1 penetrating one or more earth formations as at 12 and 13. As illustrated, the tool id is suspended in the borehole it from the lower end of a typi cal multiconductor cable 14 that is spooied in the usual fashion on a suitable winch (not shown) at the surface and coupled to the surface portion of a tool-control system 15 as well as typical recording and indicating apparatus l6 and a power supply 117. in its preferred embodiment, the tool 10 includes anelongated body 18 which encloses the downhole portion of the tool control system 15 and carries selectively-extendibie toolanchoring means i9 and new and improved fluidadmitting means 20 arranged on opposite sides. of the body as well as one or more tandemly-coupled fluid collecting chambersZi and 22.

As is explained in greater detail in a copending appiication, Ser. No. 313,235 by Harold J. Urbanosityfiied Dec. 8, 1972, the new and improved formation-testing tool 10 of the present invention and the control system 35 are cooperatively arranged so that, upon command from the surface, the tool can be selectively placed in any one or more of five selected operating positions. As will be subsequently described briefly, the control system 15 will function to either successively piece the tool in one or more of these positions or else cycle the tool between selected ones of these operating positions. These five operating positions are simply achieved by selectively moving suitable control apply power to different conductors Fill-3'7 in the cable Turning now to FlGS. 2A and 2B, the preferred embodiment of the entire downhole portion of the control system 15 as well as the tool-anchoring means 19, the

fluid-admitting means 263 and the fluid- collecting chambers 21 and 22 are schematically illustrated with their several elements or components depicted as they will respectively be arranged when the new and improved tool is fully retracted and the switches 23 and 24 are in their first or off operating positions 25. In the preferred embodiment of the selectivelyextendible tool-anchoring means l9 schematically illustrated in FIG. 2A, an upright wall-engaging anchor member 38 along the rear of the tool body lid is coupled in a typical fashion to a longitudinallyspaced pair of laterally-movable piston actuators 39 and d ll of a typical design mounted tranversely on the tool body lif As will be subsequently explained, the lateral extension and retraction of the wall-engaging member 3% in relation to the rear of the tool body ibis controlled by the control system which is operatively arranged to se' lectively admit and discharge a pressured hydraulic fluid to and from the piston actuators 39 and 4t).

borehole fluid-admitting means it) employed with the preferred embodiment of the new and improved tool 10 are cooperatively arranged for sealingoff or isolating selected portions of the wall of the horehole 11; and, once a selected portion of the borehole wall is packed-off or isolated from the well bore fluids, establishing pressure or fluid communication with the adjacent earth-formations. As depicted in H6. 2A, the fluid-admitting means preferably include an annular elastomeric sealing pad 41 mounted on the forward face of an upright support member or plate 42 that is coupled to a longitudinally-spaced pair of laterallymovable piston actuators 43 and 44 respectively arranged transversely on the tool body 18 for moving the sealing pad in relation to the forward side of the tool body. Accordingly, as the control system l5 selectively supplies a pressured hydraulic fluid to the piston actuators 43 and 44, the sealing pad 41 will be moved laterally between a retracted position adjacent to the forward side of the tool body 18 and an advanced or forwardly-extended position.

By arranging the annular sealing member 41 on the opposite side of the tool body l8 from the wallengaging member 38, the lateral extension of these two members will, of course, be effective for urging the sealing pad into sealing engagement with the adjacent wall of the borehole 11 and anchoring the tool It) each time the piston actuators 39, 40, 43 and 44 are extended. It will, however, be appreciated that the wallengaging member 38 as well as its piston actuators 39 and 40 would not be needed if the effective stroke of the piston actuators 43 and 44 would be sufiicient for assuring that the sealing member 4ll can be extended into firm sealing engagement with one wall of the borehole 11 with the rear of the tool body l8 securely anchored against the opposite wall of the borehole. Conversely, the piston actuators 43 and 44 could be similarly omitted where the extension of the wall-engaging member 38 alone would be effective for moving the other side of the tool body 18 forwardly toward one wall of the borehole it to place the sealing pad @l into firm sealing engagement therewith. However, in the preferred embodiment of the formation-testing tool 10, both the tool-anchoring means 19 and the fluidadrnitting means 2ft are made selectively ertendible to enable the tool to be operated in boreholes of substantial diameter. This preferred design of the tool it'll, of course, results in the overall strolre of the piston actuators 39 and an and the piston actuators did and dd being to a minimum so as to reduce the overall diameter of the tool body lb.

To conduct connate fluids into the new and improved tool l@, the fluid-admitting means 2t? further include an enlarged tubular member d5 having an open ion ward portion coaxially disposed within the sealing pad er and a closed rear portion which is slidably mounted within a larger tubular member secured to the rear face of the plate 42 and extended rearwardly there'- from. By arranging the nose of the tublar fluid admitting member 4% to normally protrude a short distance ahead of the forward face of the sealing pad til, extension of the fluid-admitting means 20 will engage the forward end of the fluid adrnitting member with the adjacent surface of the wall of the borehole ll as the annular sealing pad is also forced thereagainst for isolating that portion of the borehole wall as well as the nose of the fluid adrnitting member from the well bore fluids. To selectively move thetubular fluid-admitting member 45 in relation to the enlarged outer member as, the smaller tubular member is slidably disposed within the outer tubular member and fluidly, sealed in relation thereto as'by sealing members 47 and db on in wardly-enlarged end portions 439 and 55d of the outer member and a sealing member ll on an enlargeddiameter intermediate portion 2 of the inner member.

Accordingly, it will be appreciated that by virtue of the sealing members 47', id and 5t, enclosed piston chambers 53 and 5d are defined within theouter tubular member did and on opposite sides of the outwardlyenlarged portion 52 of the inner tubular member 35 which, of course, functions as a piston member. Thus, by increasing the hydraulic pressure in the rearward chamber $3, the fluid-admitting member 45 will be moved forwardly in relation to the outer tubular member 46 as well as to the sealing pad dll. Qonversely, upon the application of an increased hydraulic pressure to the forward piston chamber 54, the fluid-admitting member 45 will be retracted in'relation to the'outer member 46 and the sealing pad ill.

Pressure or fluid communication with the fluidadmitting menas 2b is controlled by means such as a generally-cylindrical valve member 55 which is coard-v ally disposed within the fluid-admitting member Q5 and cooperatively arranged for axial movement therein be tween a retracted or open position and the illustrated advanced or closed position where the enlarged forward end 56 of the valve member is substantially, if not altogether, sealingly engaged with the forwardmost interior portion of the fluid-admitting member. To support the valve member 55, the rearward portion of the valve member is axially hollowed, as at d7, and coaxially disposed over a tubular member 5h projecting for" wardly from the transverse wall 59 closing the rear end of the fluid-admitting member 4l. The axial bore 5'7 is reduced and extended forwardly along the valve member 55 to a termination with one or more transverse fluid passages in the forward portion of the valve member just behind its enlarged head as.

To provide piston means for selectively moving the valve member 55 in relation to the fluid-admitting member 45, the rearward portion of the valve member is enlarged, as at 61, and outer and inner sealing members 62 and 63 are coaxially disposed thereon and respectively sealingly engaged with the interior of the fluid-admitting member and the exterior of the forwardly-extending tubular member A sealing member 64 mounted around the intermediate portion of the valve member 55 and sealingly engaged with the interior wall of the adjacent portion of the fluid-admitting member 45 fluidly seals the valve member in relation .to the fluid-admitting member. Accordingly, it will be Those skilled in the art will, of course, appreciate that many earth formations, as at l2, are relatively unconsolidated and are, therefore, readily eroded by the withdrawal of connate fluids. Thus, to prevent any significant erosion of such unconsolidated formation materials, the fluid-admitting member 45 is arranged to define an internal annular space 67 and allow passage 68 in the forward portion of the fluid-admitting member, and a tubular screen 69 of suitable fineness is coaxially mounted around the annular space. in this manner, when the valve member 55 is retracted, formation fluids will be compelled to pass through the exposed forward portion of the screen 69 ahead of the enlarged head 56, into the annular space 67, and then through the fluid passage 60 into the fluid passage 57 and the tubular member 58. Thus, as the valvemember 55 is retracted, should loose or unconsolidated formation materials be eroded from a formation as connate fluids are withdrawn therefrom, the materials will be stopped by the exposed portion of the screen 69 ahead of the enlarged head 56 of the valve member thereby quickly forming a permeable barrier to prevent the continued erosion of loose formation materials once the valve member halts.

A sample or flow line 70 is cooperatively arranged in the formation-testing tool and has one end coupled, as by a-flexible conduit 71, to the fluid-admitting means and its other end terminated in a pair of branch conduits 72 and 73 respectively coupled to the fluidcollecting chambers 21 and 22. To control the communication between the fluid-admitting means 20 and the fluid-collecting chambers 21' and 22,, normally-closed flow-control valves 74-76 of a similar or identical design are arranged respectively in the flow line 76) and in the branch conduits 72 and 73 leading to the sample chambers. For reasons which will subsequently be described in greater detail in explaining the methods and apparatus of the present invention a normally-open control valve 77 which is similar to the normally-closed control valves 776 is cooperatively arranged in a branch conduit 7% for selectively controlling communication hetween the well bore fluids exterior of the tool i and the upper portion of the flow line 7% extending .veen the flow-line control vmve 74 and the fluidadmitting means 2 1 As illustrated, the control valve 77 employed in the present invention is comprised ol'a valve body 7? cooperatively carrying a typical. piston actuator which is normally biased to an elevated position by a spring fill of a predetermined strength. A valve member 32 coupled to the piston actuator 30 is cooperatively arranged for blocking fluid communication between the inlet and outlet fluid ports of the control valve whenever the valve member is moved" to its lower position. The control valves id-76 are similar to the control valve 77 except that a spring of selected strength is respectively arranged in each for normally biasing each of these valve members to a closed position As shown in FIGS. Silt-2B5, a branch conduit $3 is coupled to the flow line ill at a convenient location between the sample chamber control valves and "7c and the flow-line control valve 74, with this branch conduit being terminated at an expansion chamber dd a predetermined volume. A reduced-diameter displacement piston tlfi is operatively mounted in the chamber 843 and arranged to be moved between selected upper and lower positions therein by a typical piston actuator shown generally at he. Accordingly, it will be appreciated that upon movement or" the displacement pistonhS from its lower position as illustrated in Flt}. 2A to an elevated or upper position, the combined volume of whatever fluids that are then contained in the branch conduit $35 as well as in that portion of theflow line ill between the flow-line control valve 7d and the sample chamber control valvesifi and 76 will be correspondingly increased.

As best seen in FlG. 2A, the preferred embodiment of the control system 15 further includes a pump $7 that is coupled to a driving motor @tl and cooperatively arranged for pumping a suitable hydraulic fluid such as oil or the like from a reservoir 8% into a. discharge or outlet line 90. Since the tool lll is to be operated in well bores, as at ll, which typically contain dirty and usually corrosive fluids, the reservoir 89 is preferably arranged to totally immerse the pump i557 and the motor dd inthe clean hydraulic fluid. inasmuch as the formation-testing tool it) must operate at extreme depths, the reservoir 89 is provided with an inlet hi for well bore fluids and an isolating piston 92 is movably arranged in the reservoir for maintaining the hydraulic fluid contained therein at a pressure about equal to the hydrostatic pressure at whatever depth the tool is then situated. A spring 93 is arranged to act on the piston 92 for maintaining the pressure of the hydraulic fluid in the reservoir @9 at an increased level slightly above the well returning hydraulic fluid from the control system E to the reservoir 89 during the operation of the tool ill.

The fluid outlet line is divided into two major branch lines which are respectively designated as the "set line and the retract" line 97 To'control the admission of hydraulic fluid to the Wet and r mit-act lines or and W7, a pair oi nationally-closed solenoid actuated valvee lid and w are coop-crntiveiy arranged to selectively admit hydraulic fluid to the two lines as the control switch 23 at the surface is mlectively pcsitioned; and a typical checlt valve Mill) is arranged in the "set" line 96 downstream of the control valve 9% for preventing the reverse flow of the hydraulic fluid when ever the pressure in the set line is greater than that then existing in the fluid outlet line no. Typical pressure switches lull-E03 are cooperatively arranged in the "set" and "retract" lines an and @7 for aelectively diecontinuing operation ot' the pump ti? whenever the pressure of the hydraulic fluid in either of these lines reaches a desired operating preasure and then restartl5 in; speed. Accordingly. the control tyrtem i5 is coop- ZJ eratively arranged no that each time the pump $7 is to be started. the control valve W (if it is not already open) as well as a third normally-closed solenoidactuated valve 3% will be temporarily opened to bypass hydraulic fluid directly from the output line W to the reservoir 89 by way of the return line 94. Once the motor 88 has reached operating speed, the bypass valve 104 will, of course, be recloaed and either the set" line control valve 98 or the retract" line control valve 99 will be selectively opened as required for that particular operational phase of the tool it). It should be noted that during those times that the "retract" line control valve 99 and the fluid-bypass valve lllll are opened to allow the motor 8% to reach its operating speed, the check valve RM will function to prevent the reverse flow of hydraulic fluid from the set" line when the "set" line control valve 9% is open.

Accordingly. it will be appreciated that the control system cooperates for selectively supplying pre sured hydraulic fluid to the set" and retract" lines up and 97. Since the pressure switches lfll and 102 respectively function only to limit the pressures in the set" and retrmf' lines to a selected maximum preesure range commensurate with the rating of the pump 87, the new and improved control system id is further arranged to cooperatively regulate the pressure of the hydraulic fluid which is being supplied at various times to selected portions of the system. Although this regulation can be accomplished in difl'crent manners, it IS preferred to employ a number of pressure-actuated control valves such as shown schematically at 105-108 in FIGS. 2A and 2B. As shown in H6. 2A. the control valve I05, for example, includes a valve body I09 having a valve seat lltl coaxially arranged therein between inlet and outlet fluid ports. The upper portion of the valve body W9 is enlarged to provide a piston cylinder Ill carrying an actuating piston H2 in coincidental alignment with the valve seat Hill. A spring ll} of a predetermined strength is arranged for normull y urging the actuating piston ill toward the valve seat lid and a control port lid is provided for admitting hydraulic fluid into the cylinder ill at a sufi'rcicnt pressure to overcome the force or this whene the P it to be eeloctively moved nwny from the vnlve seet- Eiuce the control system id operates at premuret fi lees than the hydrostatic pressure of the well bore fluh relief port M5 is provided in the valve body W for communicating the space in the cylinder ill above the actuating piston Hi2 with the reeervoir 89. A valve monitor lid complcrnentally shaped for seating engagement with the valve seat lid is cooperatively coupled to th: actuating piston Hi2 as by an upright stern ll? which is slidably disposed in an axial bore lid in the piston. A spring lid oi selected st ength is disposed in the axial bore lid for normally urging the valve member said enclosed into seating engagement with the valve seat lid.

Accordingly, in its operating position depicted in Flt]. 2A., the control valve W5 (as well as; the valve Mid) will simply function as a normally closed check valve. This is to say. in this operating position. hydraulic fluid can flow only in a reverse direction whenever the pressure at the valve outlet is sufficiently greater than the inlet preesurc to elevate the valve member l lti from the valve seat lid against the predetermined clue ing force preatureactuated by the spring H9. 0n the other hand. when sufficient fluid prertaure is applied to the control port lid for elevating the actuating piston. oppoeed shoulders, at at lZti, on 23 the stern ii"? and the piston H2 will engage for elevating the valve membet llti from the valve seat lid.

As shown in HUS. 2A and 2%, it will be appreciated that the control valve ill? (at well an the valve 3%) is similar to the control valve rat except that in the firetrnentioned control valve, the valve member lZl is prelerably rigidly coupled to its associated actuating piston H22. Thus, the control valve 107 (as well as the valve Mid) has no alternate checking action allowing reverse flow and is simply a normally-cloned pressure-actuated valve for selectively controlling fluid communication between its inlet and outlet ports. lrlereagain. the hydraulic pressure at which the control valve W? (as well as the valve W8) is to selectively open is go erned by the predetermined strength ot" the spring H3 normally biasing the valve member to its closed position.

The set line downstream of the check valve llltll is comprised of a low-pressure section we having one branch 125 coupled to the fluid inlet of the control valve Hi7 and another branch lilo which is coupled to the fluid inlet of the control valve lil to selectively supply hydraulic fluid to a high-presume section ll? of the set" line which is itselfterm nated at the fluid inlet of the control valve E08. lo regulate the supply oi hydraulic fluid from the low-pressure section lid to the high-pressure section l2? of the set" line 96, a pressure-communicating line i253 s coupled between the low-pressure section and the control rt ofthe control valve 105. Accordingly so long 25 t. e pressure of the hydraulic fluid in the low-pressure section of the set" line remains below the redctermined actuating pressure required to open t e control valve N5, the high-pressure section 127 will b:- isolatcd from the lowpressure section l24. Conversely. once the hydraulic preasure in the low-pressure line KM reaches the predetermined actuating prcssure of the valve W53 the control valve will open to admit the hydraulic fluid into the high-pressure line E27.

The control valves 107 and W8 are respectively arranged to selectively communicate the low-pressure and high-pressure sections llZd and 127 of the {Hit line 96 with the fluid reservoir kil s. To accomplish this, the control ports of the two control valves 107 and litltl are each connected to the retract" line 97 by suitable pressure-communicating lines i239 and lii ll. Thus, whenever the pressure in the retract line 97 reaches their respective predetermined actuating levels, the control valves 107 and N8 will be respectively opened to selectively communicate the two sections 7124 and 127 of the set" line with the reservoir 8% by way of the return line 96 coupled to the respective outlets of the two control valves.

As previously mentioned, in FlGS. ZA-ZB the tool ill and the sub-surface portion of the control system l are depicted as their several components will appear when the tool is retracted. At this point, the wallengaging member 38 and the sealing pad ll are respectively retracted against the tool body E8 to facilitate passage of the tool 10 into the borehole ll. To prepare the tool Ill) for lowering into the borehole ill, the switches 23 and 24 are moved to their second or initialization positions 26. At this point, the hydraulic pump $7 is started to raise the pressure in the retract line 97 to a selected maximum to be certain that the pad 41 and the wall-engaging member 3% are fully retracted. As previously mentioned, the control valves W and 104 will be momentarily openedwhen the pump 87 is started until the pump motor 88 has reached its operating speed. At this time also, the control valve '77 is open and that portion of the flow line '70 between the closed flow-line control valve 74 and the fluidadmitting means 20 will be filled with well bore fluids at the hydrostatic pressure at the depths at which the tool 10 is then situated.

When the tool it) is at a selected operating depth, the switches 23 and 24 are advanced to their third positions 27. Then, once the pump $7 has reached its rated operating speed, the hydraulic pressure in the output line 90 will rapidly rise to its selected maximum operating pressure as determined by the maximum or off setting of the pressure switch W1. As the pressure progressively rises, the control systems will successively function at selected intermediate pressure levels for sequentiallyoperating the several control valves 395-108 as described fully in the aforementioned copending application, Ser. No. 313,235. v

Turning now to FIG. 3., selected portions of the control system 15 and various components of the tool iii are schematically represented to illustrate the operation of the tool at about the time that the pressure in the hydraulic output line 90 reaches its lowermost intermediate pressure level. To facilitate an understanding of the operation of the tool It) and the control system 15 at this point in its operating cycle, only those components which are then operating are shown in FIG. 3.

At this time, since the control switch 23 (FIG. 1) is in its third position 27, the solenoid valves 98 and We will be open; and, since the hydraulic pressure in the set" line 96 has not yet reached the upper pressure limit as determined by the pressure switch lllll, the pump motor 88 will be operating. Since the control valve H05 (not shown in H0. 3) is closed, the highpressure section 127 of the set line 96 will still be iso lated from the low-pressure section 11%. Simultaneously, the hydraulic fluid contained in the forward pressure chambers of the piston actuators 3%, d0, d3

and dd will be displaced (as shown by the arrows as at Ellill) to the retract linefl' l and returned to the reservoir 39 by way of the open solenoid valve res. These actions will, of course, cause the wall-engaging member Bill as well as the sealing pad dl to be respectively extended in opposite lateral directions until each has moved into iirm engagement with the opposite sides of the borehole ll.

it will be noticed in FlG, 3 that hydraulic fluid will be admitted by way of branch hydraulic lines i332 and 33 to the enclosed annular chamber 53 to the rear of the enlargeddiameter portion 52 of the iluid-admitting member 55. At the same time, hydraulic liuid from the piston chamber 54 ahead of the enlarged-diameter postion 52 will be discharged by way of branch hydraulic lines 11% and 113.55 to the retract line all for progres sively moving the lluid adrnitting member 55 forwardly in relation to the sealing member ill until the nose of the fluid-admitting member 35 engages the wall of the borehole iii and then halts. The sealing pad 4i is then urged forwardly in relation to the now-halted tubular member until the pad sealingly engages the borehole wall for packing-oi? or isolating the isolated wall portion from the well bore fluids.

it should also be noted that although the pressured hydraulic fluid is also admitted at this time into the "forward piston chamber as between the sealing members d2 and 6 on the valve member 55, the valve member is temporarily prevented from moving rcarwardly in re lation to the inner and outer tubular members 4;? and inasmuch as the control valve (not shown in H61. 3) is still closed thereby temporarily trapping the hydraulic fluid in the rearward piston chamber as to the rear of the valve member. The significance of this delay in the retraction of the valve member 1% will be subsequently explained.

As also illustrated in FIG. 3, the hydraulic fluid in the low-pressure section 12% of the set line as will also be directed by way of a branch hydraulic line lilo to the piston actuator $6, This will, of course, result in the displacement piston rid being elevated as the hydraulic fluid from the piston actuator is returned to the retract line 97 by way of a branch hydraulic conduit 137. As will be appreciated, elevation of the displace ment piston $5 in the expansion chamber M will be ef fective for significantly decreasing the pressure initially existing in the isolated portions of the branch line $3 and the flow line between the still-closed flow-line control valve 74 and thestill-closed chamber control valve 75 and re (not seen in FlG. 3). The purpose of this pressure reduction will be subsequently explained.

H6. 3, it will be appreciated that the hydraulic pres sure delivered by the pump 87 will again rise. Then, once the pressure in the output line 9% has reached its second intermediate level of operating pressure, the control valve 106 will open in response to this pressure level to now discharge the hydraulic fluid previously trapped in the piston chamber 6:3 to the rear of the valve member 55 back to the reservoir 8i As illustrated, in FIG. 4, once the control valve the opens, the hydraulic fluid wil be displaced from the rearward piston chamber 65 by way of branch hydraw lic lines lfih, 139 and 35 to the retract" line til? as pressured hydraulic fluid from the set line 55b surges into the piston chamber on ahead of the enlargeddiameter portion tSl of the valve member 555. This will, of course, cooperate to rapidly drive the valve member 55 rearwardly in relation to the now-halted fluidadmitting member 45 for establishing fluid or pressure communication between the isolated portion of the earth formation 12 and the flow passages $7 and so in the valve member by way of the filter screen 6%.

Although this is not fully illustrated i, it will be recalled from FlGS. 2A and 28 that the control valves 74-76 are initially closed to isolate the lower portion of the flow line 7% between these valves as well as the branch line 83 leading to the pressures-reduction chamber as. However, in keeping with the principles of the present invention, the flowline pressure-equalizing control valve 77 will still be open at the time the control valve W6 opens to retract the valve member 55 as depicted in FIG. 4. Thus, as the valve member progressively uncovers the filtering screen as, well bore fluids at a pressure greater than that of any connate fluids which may be present in the isolated earth formation 12 will be introduced into the upper portion of the flow line 70 and, by way of the flexible conduit member 71, into the rearward end of the tubular member 58. As these high-pressure well bore fluids pass into the annular space 67 around the filtering screen 69, they will be forcibly discharged (as shown by the arrows Mil) from the forward end of the fluid-admitting member 35 for washing away any plugging materials such as mudcake or the like which may have become deposited on the internal surface of the filtering screen when the valve member 55 fitst uncovers the screen. Thus, to attain the objects of the present invention, the control system 15 is operative for providing a momentary outward surge or reverse flow of well bore fluids for cleansing the filtering screen 69 of unwanted debris or the like before a sampling or testing operation is commenced.

It will be appreciated that once the several components of the formation-testing tool it) and the control system 15 have reached their respective positions as depicted in H6. 4, the hydraulic pressure in the output line 90 will again quickly increase to its next intermediate pressure level. Once the pump 87 has increased the hydraulic pressure in the output line 2% to this next predetermined intermediate pressure level, the control valve l05 will selectively open as depicted in H6. 5A. As seen there, opening of the control valve 105 will be effective for now supplying hydraulic fluid to the highpressure section 127 of the set" line 96 and two branch conduits M1 and M2 connected thereto for successively closing the control valve 77 and then opening thecontrol valve 74L In this manner, as depicted by the several arrows at 143 and 144, hydraulic fluid at a pressure representative of the intermediate operating level will be supplied by way of a typical check valve 145 to the upper portion of the piston cylinder ms of the normally-open control valve 77 as fluid is exhausted from the lower portion thereof by way of a conduit M7 coupled to the retract" line 97. This will, of course, be effective for closing the valve member 82 so as to now block further communication between the flow line 70 and the well bore fluids exterior of the tool lb. Simultaneously, the hydraulic fluid will also be admitted into the lower portion of the piston cylinder Mb of the control valve 7d.

By arranging the biasing spring bl for the normallyopen control valve 77 to be somewhat wealter than the biasing spring M9 for the normally-closed control valve 74., the second valve will be momentarily retained in its closed position until the first valve has had time to close. Thus, once the valve 77 closes, as the hydraulic iluid enters the lower portion of the piston chamber of the control valve 7d, the value member lfill'will be owned as hydraulic fluid is exhausted from the upper portion of the chamber through a typical check valve 15R and a branch return line l2 coupled to the retracd line 97.

it will be appreciated therefore, that with the tool in the position depicted in FlGS. 5A and 5B, the flow line Ill is now isolated from the wall bore lluids and is in communication with the isolated portion of the earth formation H by way of the flexible conduit 7t. it will also be recalled from the preceding discussion of 3 that the branch flow line $3 as well as the portion of the main flow line 7tl between the flow -line control valve 7 and the sample chamber control valves 75 and were previously expanded by theupward movement of the displacement piston $5 in the reduced-volume chamber as. Thus, upon opening of the flow-line control valve 74, the isolated portion of the earth forrnation 3.22 will be communicated with the reducedpressure space represented by the previously-isolated portions of the flow line and the branch conduit 83.

Of particular interest to the present invention, it should be noted that should the formation 12 be relatively unconsolidated, the rearward movement of the valve member 55 in cooperation with the forward movement of the fluid-admitting member &5 will allow only those loose formation materials displaced by the advancement of the fluid-admitting member into the formation to enter the fluid-admitting member. This is to say, the fluid-admitting member 35 can advance into the formation l2 only by displacing loose formation materials; and, since the space opened by the rearward displacement of the valve member is the only place into which the loose formation materials can enter, ther erosion of the formation materials will be halted once the fluid-admitting member has been tilled with loose materials as shown in l-lG. db. On the other band, should a formation interval which is being tested be relatively well-compacted, the advancement of the fluidadmitting member 45 will be relatively slight with its nose making little orno penetration into the isolated earth formation. lt will, of course, be appreciated that the nose of the fluid-admitting member d5 will be urged outwardly with sufficient force to at least penetrate the mudcalce which typically lines the borehole walls adjacent to permeable earth formations. in this situation,

however, the forward movement of the fluid-admitting member 45 will be unrelated to the rearward movement of the valve member 55 as it progressively uncovers the filtering screen 69. in either case, the sudden opening of the valve 74 will cause mudcake to be pulled to the rear of the screen d9 to leave it clear for the subsequent passage of connate fluids.

AS best seen in FlGS. 5A and 58, therefore, should there be any producible connate fluids in the isolated earth formation 12, the formation pressure will be effective for displacing these connate fluids by way of the fluid-admitting means 20 into the flow line until such time that the lower portion of the flow line 7b and the branch conduit 83 are filled and pressure equilibrium is established in the entire flow line. By arranging a typical pressure-measuring transducer, as at 153 (or, if desired, one or more other suitable transducers) in the flow line 70, one or more measurements representative of the characteristics of the connate fluids and the formation 12 may be transmitted to the surface by a conductor 154 and, if desired, recorded on the recording apparatus 16 (FIG. l). The pressure measurements provided by the transducer 153 will, of course, permit the operator at the surface to readily determine the formation pressure as well as to obtain one or more indications representative of the potential producing ability of the formation 12. The various techniques for analyzing formation pressures as well known in the art and are, therefore, of no significance to understanding the present invention.

It will be recognized, of course, that by virtue of the purging action which was previously provided by the outflowing well bore fluids in the practice of the pres ent invention, there is a reasonable assurance that the filtering screen 69 will have been cleared of plugging materials such as mudcake of formation materials that may otherwise plug the fluid-admitting means 20. However, the sudden introduction of connate fluids into the flow line 70 will also be effective for clearing the screen 69 of residual plugging materials.

The measurements provided by the pressure transducer 153 at this time 'will indicate whether the sealing pad 41 has'fin fact, established complete sealing en'- gagement with the earth formation 12 inasmuch as the expected formation pressures will .be recognizably lower than'the hydrostatic pressure of the well bore fluids at the particular depth which the tool 10 is then situated. This ability to determine the effectiveness of the sealing engagement will, of course, allow the operator to retract the wall-engaging member 38 and the sealing pad 41 without having to unwittingly or needlessly continue the remainder of the complete operating sequence.

Assuming, however, that the pressure measurements provided by the pressure transducer 153 show that the sealing pad 41 is firmly seated, the operator may leave the formation-testing tool 10 in the position shown in FlGS. A and 58 as long as it is desired to observe as well as record the pressure measurements. As a result,

the operator can determine such things as the time required for the formation pressure to reach equilibrium as well as the rate of increase and thereby obtain valu able information indicative of various characteristics of the earth formation 12 such as permeability and porosity. Moreover, with the new and improved tool 10, the operator can readily determine if collection of a fluid sample is warranted.

Once the several components of the tool and the control'system 15 have moved to their respective positions shown in FIGS. 5A and 5B, the hydraulic pressure will again rise until such time that the setline pressure switch 101 operates to halt the hydraulic pump 87. Inasmuch as the pressure switch 101 has a selected operating range, in the typical situation the pump 87 will be halted shortly after the control valve 77 closes and the control valve 74 opens. At this point in the operating cycle of the tool it), once a sufficient number of pressure measurements have been obtained, a decision can be made whether it is advisable to obtain one or more samples of the producible connate fluids present in the earth formation 112. If such samples are not desired, the operator can simply operate the "control switches 23 and 24 for retracting the wall-engaging member 33 as well as the sealing pad 4i without further ado.

On the other hand, should a fluid sample be desired, the control switches 23 and 24 (FIG. l) are advanced to their next or so-called "sample" positions 28 to open, for example, a solenoid valve l5 (FIG. 2B) for coupling pressured hydraulic fluid from the highpressure section 127 of the set litie 96 to the piston actuator 156 of the sample chamber control valve V55. This will, of course, be effective for opening the control valve 75 to admit connate fluids through the flow line "70 and the branch conduit 72 into the sample chamber 21. if desired, a chamber selection" switch E57 in the surface portion of the system 15 could also be moved from its first sample position ih to its so-called second sample position 115% (l ltii. l) to energize a solenoid valve loll (FIG. 2B) for opening the control valve '76 to also admit connate fluids into the other sample chamber 22. In either case, one or more sampies of the connate fluids which are present in the iso lated earth formation 12 can be selectively obtained by the new and improved tool it).

Upon moving the control switches 23 and 24 to their so-called sample-trapping positions 29, the pump $7 will again be restarted. Once the pump 3'7 has reached operating speed, it will commence to operate much in the same manner as previously described and the hydraulic pressure in the output line ll will begin rising with momentary halts at various intermediate pressure levels.

Accordingly, when thecontrol switches 23 and 24 have been placed in their sample trapping" positions 29, the solenoid valve W will open to now admit hydraulic fluid into the retract line 9'7. By means of the electrical conductor lllfia (PEG. it however, the pressure switch W3 is enabled and the pressure switch it'iZ is disabled so that in this position of the control switches 23 and 24 the maximum operating pressure which the pump 87 can initially reach is limited to the @Q, the pressure in this portion of the set line will be rapidly decreased to close the control valve 195 once the pressure in the line is insufficient to hold the valve open. Once the control valve W5 closes, the pressure remaining in the low-pressure section E24 of the set line 96 will remain at a reduced pressure which is nevertheless effective for retaining the wall-engaging member 38 and the sealing pad 41 fully extended.

As the hydraulic fluid is discharged from the lower portion of the piston actuator 11% by way of the stillopen solenoid valve and fluid from the .retract" line 97 enters the upper postion of the actuator by way of a branch line 16H, the chamber control valve "i will close to trap the sample of connate fluids which is then present in the sample chamber 2i. Similarly, should there also be a fluid sample in the other sample charm ber 22, the control valve 76 can also he readily closed by operating the switch 157 to reopen the solenoid valve 160. Closure of the control valve (as well as the valve 76) will, of course, be effective for trapping any fluid samples collected in one or the other or both of the sample chambers 21 and 22-.

Once the control valve 75 (and, if necessary, the control valve '76) has been reclosed, the control switches 23 and 24 are moved to their next or so-called retract switching positions 3% for initiating the simultaneous retraction of thewall-engaging member 38 and the sealing pad ll. in this final position of the control switch 24, the pressure switch 103 is again rendered inoperative and the pressure switch W2 is enabled so as to now permit the hydraulic pump $7 to be operated at full rated capacity for attaining hydraulic pressures greater than the first intermediate operating level in the retract" cycle. Once the pressure switch W3 has again been disabled, the pressure switch M2 will now function to operate the pump d7 so that the pressure will now quickly rise until it reaches the next operating leveL- At this point, hydraulic fluid will be supplied through the retract line 97 and the branch hydraulic line lid? for reopening the pressure-equalizing control valve 7'7 to admit well bore fluids into the flow line 7d. Opening of the pressure-equalizing valve 77 will admit well bore fluids into the isolated space defined by the sealing pad 41 so as to equalize the pressure differential existing across the pad. Hydraulic fluid displaced from the upper portion of the piston chamber M6 of the control valve'7'7 will be discharged through a typical relief valve lei which is arranged to 'open'only in response to pressures'equal or greater than that of this-present operating level. The hydraulic fluid displaced from the piston chamber l46 through the relief valve ldl will be returned to the reservoir 89 by way of the branch hydraulic line 141, the high-pressure section E27 of the set" line 96, the still-open control valve idli, and the return line 94.

When the hydraulic pressure in the output line 90 has either reached the next operating level or, if desired, a still-higher level, pressured hydraulic fluid in the retract line 97 will reopen the controlvalve 107 to communicate the low-pressure section H24 of the set" line 96 with the reservoir 89. When this occurs, hydraulic fluid in the retract" line will be admitted to the retract side of the several piston actuators 39, 40, 43 and 44. Similarly, the pressured hydraulic fluid will also be admitted into the annular space 54 in front of the enlarged-diameter piston portion 52 for retracting the fluid-admitting member 45 as well as into the annular space 66 for returning the valvemember 55 to its forid 3.51 is held in a closed position until the increasing hydraulic pressure developed by the pump 37 exceeds the operating level used to retract the wall-engaging mem fill and the sealing pad dl. At this point in the operating sequence of the new and improved tool iii, the flow-line control valve "7d will be reclosed.

The pump 8? will, of course, continue to operate until such time that the hydraulic pressure in the output line 98? reaches theupper limit determined by setting oi the pressure switch W2, At some convenient time thereafter, the control switches 23 and M are again returned to their initial or of? positions E for halting further operation of the pump motor d5) as well as reopening the solenoid valve 1% to again communicate the retract" line F7 with the fluid reservoir 89. This completes the operating cycle of the new and improved tool ill.

Referring again to ilG. d, it will be appreciated that the new and improved methods of the present invention will assure that communication will be established between the flow line 76 and the formation, as at E2, before any measurements or samples are taken. For example, should the interior surface of the filtering screen become unduly coated with particles of the relatively-imperrneable mudcalte as the valve member moves to its rearward position, opening of the valve member will be effective for developing a significant reverse flow of the higher-pressure well bore fluids through the screen 69 and into the lower-pressure formation 12. Similarly, should extremely-fine particles of sand or the like from the formation l2 be lodged against the interior surfaces of the filter medium as, this reverse flow of well bore fluids will be effective for cleansing the filter before any tests are made.

Accordingly, in keeping with the objects of the present invention, since the control valve 77 is open to admit well bore fluids into the upper portion of the flow line '70, when the valve memmr 55 is opened the filtering screen M will be thoroughly cleansed by the outward surge of well bore fluids. Thus, when the formation 12 is subsequently communicated with the re duced or atmospheric pressure initially present n the ward position. The hydraulic fluid exhausted from the several piston actuators 39, 40, 43 and 44 as well as the piston chambers 54 and 66 will be returned directly to the reservoir 89 by way of the high-pressure section 124 of the set" line 96 and the control valve 107. This action will, of course, retract the wall-engaging member 38 as well as the sealing pad 4i against the tool body 18 to permit the tool 10 to be either repositioned in the well bore ll or returned to the surface if no further testing'is desired.

it should be noted that although there is an operating pressure applied to the upper portion of the piston cylinder 148 for the flow-line control valve 74 at the time that the control valve 77 is reopened, a normally-closed relief valve M52 which is paralleled with the check valve previously-isolated lower portion of the flow line 7%, producible connate fluids in the isolated portion of the formation will be drawn into the flow line. it will, of course, be recognized that if, on the other hand, there are no producible connate fluids in the formation 12, the pressure readings provided by the transducer E53 will simply indicate little or no pressure rise in the flow line '70. in either case, the operator at the surface will be reliably assured that a failure to obtain a significant pressure increase in the flow line measurements is in fact caused by a non-producible formation and is not unknowingly attributed to a tightly-plugged filter screen 69 instead. Moreover, the new and improved methods of the present invention are of equal advan tage when a sample of connate fluids is to be taken as well. Thus, instead of obtaining little or no flow of fluid which would occur with at least a partially-blocked screen as, the reverse flushing of the filter will assure the operator that the screen is clean so that formation fluids are free to flow into the tool M; This can clearly reduce the time required to perform a typical testing operation.

While only a particular embodiment of the present invention and one mode of practicing the invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is: l. A method for testing earth formations traversed by a well bore and comprising the steps of:

engaging fluid-admitting means coupled by a fiitering medium to a fluid passage against a waii surface of said well bore adjacent to an earth formation be lieved to contain producibie connate fluids for isolating said wall surface from fluids in said weii bore and placing said fluid-admitting means in position for receiving connate fluids from said earth formation; discharging said well bore fluids from said fluid passage in a reverse direction through said filtering medium and into said fluid-admitting means and said earth formation for cleansing said filtering medium; and, thereafter, communicating said fluid passage with an enclosed chamber initially at a reduced pressure for drawing producible connate fluids from said earth formation and in the opposite direction through said filtering medium and into said fluid passage to obtain a filtered sample of said connate fluids in said enclosed chamber. 2. The method of claim 1 further including the additional step of:

measuring the pressure in saidenclosed chamber and said fluid passage for obtaining at least one pressure measurement indicative of at least one characteristic of said earth formation. 3. The method of claim 1 further including the additional steps of:

monitoring at least one characteristic of said filtered sample drawn into said fluid passage for obtaining a series of measurements representative of the production characteristics of said earth formation; and, thereafter, discontinuing further communication between said fluid passage and said enclosed chamber for trapping said filtered sample therein. 4. The method of claim 1 further including the additional steps of:

monitoring at least one characteristic of said filtered sample drawn into said fluid passage for obtaining a series of measurements representative of the production characteristics of said earth formation; and, thereafter, expelling said filtered sample from said enclosed chamber. 5. A method for testing earth formations traversed by a well bore and comprising the steps of:

urging fluid-admitting means including a normallyclosed fluid-sampling member coupled by a filtering medium to a fluid passage into sealing engagement with a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids for isolating said wall surface from fluids in said well bore and placing said fluidsampling member in position for subsequently communicating with said earth formation; opening said fluid-sampling member and admitting said well bore fluids into said fluid passage for passing said wellbore fluids through said filtering meiii dium and said fluid-sampling member into said earth formation to cleanse said filtering medium sand said fluid-sampling member of potentiallyplugging materials; closing communication between said weli bore fluids and said fluid passage; and, thereafter, coupling an enclosed reduced-pressure chamber to said fluid passage for drawing producibie con'nae fluids from said earth formation through said sampling member and said filtering medium and into said fluid passage to obtain a filtered sarnpie of said connate fluids in said enclosed chamber. ti. The method of claim 5 further inciuding the additional step of:

uncoupling said enclosed chamber from said fluid passage for collecting said fiitered sample. 7. The method of claim 5 further including the additional steps of:

monitoring the pressure in said fluid passage for obtaining a series of pressure measurements represen tative of the production characteristics said earth formation; and uncoupling said enclosed chamber from said fluid passage for collecting said fi tered sample in said enclosed chamber. d. The method of claim 5 further including the additional steps of:

monitoring the pressure in said fluid passage for obtaining a series of pressure measurements representative of the production ci'zaracteristics of said earth formation; expelling said filtered sampie from said enciosed chamber and uncoupling saidenciosed chamber from said fluid passage; reclosing said fluid-sampling member; reducing the pressure in said enclosed chamber; removing said fluid-admitting means from said wall surface and urging said fluid-admitting means into sealing engagement with another waii surface of said well bore adjacent to another earth formation believed to contain producible connate fluids for isolating said other wall surface from said weil bore fluids and placing said fluid-sampling member in position for subsequently communicating with said other earth formation; re-opening said fluid-sampling member and readmitting said well bore fluids into said fluid passage for passingsaid well bore fluids through said filtering medium and said fluid-sampling member into said other earth formation to recleanse said filtering medium and said fluid-sampling member-of potentially-plugging materials; reclosing communication between said well bore fluids and said fluid passage; recoupling said enclosed chamber to said fluid passage for drawing producible connate fluids from said other earth formation through said fluidsampling member and said filtering medium and into said fluid passage to obtain a filtered sample of said connate fluids from said other earth formation in said enclosed chamber; and. remonitoring the pressure in said fluid passage for obtaining a second series of pressure measurements representative of the production characteristics of said other earth formation. 9. The method of claim 5 further including the additional steps of:

monitoring the pressure in said fluid passage for obtaining a series of pressure measurements representative of the production characteristics of said earth formation;

coupling a sample receiver at a reduced pressure to said fluid passage for collecting filtered connate fluids from said earth formation in said sample receiver;

closing said sample receiver for entrapping connate fluids collected therein;

expelling said filtered sample from said enclosed chamber and uncoupling said enclosed chamber from said fluid passage;

reclosing said fluid-sampling chamber;

removing said fluid-admitting means from said wall surface and urging said fluid-admitting means into sealing engagement with another wall surface of said well bore adjacent to another earth formation believed to contain producible connate fluids for isolating said other wall surface from said well bore fluids and placing said fluid-sampling member in position for subsequently communicating with said other earth formation;

re-opening said fluid-sampling member and re admitting said well bore fluids into said fluid passage for passing said well bore fluids through said filtering medium and said fluid-sampling member into said other earth formation to recleanse saidfiltering medium and said fluid-sampling member of potentially-plugging materials;

reclosing communication between said well bore fluids and said fluid passage;

recoupling said enclosed chamber to said fluid passage for drawing producible connate fluids from said other earth formation through said fluidsampling member and said filtering medium and into said fluid passage to obtain a filtered sample of said connate fluids from said other earth formation in said enclosed chamber; and

remonitoring the pressure in said fluid passage for obtaining a second series of pressure measurements representative of the production characteristics of said other earth formation.

10. The method of claim 9 further including the additional step of:

following the remonitoring step, coupling a second sample receiver at a reduced pressure to said fluid passage for collecting filtered connate fluids from said other earth formation in said second sample receiver; and I closing said second sample receiver for entrapping connate fluids collected therein.

11. The method of claim further including the additional steps of:

monitoring the pressure in said fluid passage for obtaining 21 series of pressure measurements representative of the production characteristics of said earth formation;

expelling said filtered sample from said enclosed chamber and uncoupling said enclosed chamber from said fluid passage;

reclosing said fluid-sampling member;

reducing the pressure in said enclosed chamber;

removing said fluid-admitting means from said wall surface and urging said fluid-admitting means into sealing engagement with another wall surface of said well bore adjacent to another earth formation believed to contain producible connate fluids for isoiating said other wail surface fromsaid well bore fluids and placing said fluid-sampling giember in position for subsequently communicating with said 7 other earth formation;

re-opening said fluid-sampling member and readmitting said well bore fluids into said fluid passage for passing said weil bore fluids through said filtering medium and said fluid-sampling member into said other earth formation to recleanse said Hi tering medium and said fluid-sampling member of potentially-plugging materials;

reclosing communication between said well bore fluids and said fluid passage;

recoupling said enclosed chamber to said fluid pas sage for drawing producible connate fluids from said other earth formation through said fluid sampling member and said filtering medium and into said fluid passage to obtain a filtered sample of said connate fluids from said other earth formation in said enclosed chamber;

remonitoring the pressure in said fluid passage for obtaining 'a second series of pressure measurements representative of the production characterisby a well bore and comprising the steps of:

urging fluid-admitting means including a fluid passage coupled by a filtering medium to a fluidsampling member having a normally-closed forward end and a rearward portion to the rear of said filtering medium into sealing engagement with a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids for isolating said wall surface from fluids in said well bore and placing said closed end of said fluid-sampling member into position for subsequently receiving connate fluids from said earth formation;

opening said normally-closed forward end of said fluid-sampling member and admitting said well bore fluids into said fluid passage for passing said well bore fluids through said filtering medium and said fluid-sampling member into said earth formation to cleanse said filtering medium and said fluidsampling member of potentially-plugging materials;

closing communication between said well bore fluids and said fluid passage;

expanding the volume of an enclosed test chamber coupled to said fluid passage downstream of said filtering medium for reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure;

after said test chamber is expanded, coupling said test chamber to said fluid passage at a speed sufficient to quickly induct a filtered sample of producible connate fluids from said earth formation into said expanded test chamber for momentarily reducing the pressure of said connate fluid sample to about atmospheric pressure and displacing loose plugging materials from said wall surface into said rearward portion of said fluidsampiing member to the rear of said filtering medium; and

monitoring the pressure in said expanded test chamber for obtaining a series of pressure measurements indicative of the production capabilities of said earth formation.

13. The method of claim l2 further including the additional step of:

recording said pressure measurements for obtaining a record representative of the pressure characteristics of said earth formation as connate fluids are produced therefrom. 14. The method of claim l2 further including the additional step of:

after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage down stream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation. 15. The method of claim l2 further including the ad ditional steps of: s

after the pressure-monitoring step, reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore; uncoupling said test chamber from said fluid passage;

reclosing said normally-closed forward end of said fluid-sampling member;

re-opening said normally-closed forward end of said fluid-sampling member and re-admitting said well bore fluids into said fluid passage for again passing said well'bore fluids through said filtering medium and said fluid-sampling member into said earth formation to recleanse said filtering medium and said fluid-sampling member for potentially-plugging materials;

reclosing communication between said well bore fluids and said fluid passage;

re-expanding the volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure;

after said test chamber is re-expanded, re-coupling said re-expanded test chamber to said fluid passage at a speed sufficient to quickly induct a second filtered sample of producible connate fluids into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure and displacing additional loose plugging materials from said wall surface into said rearward portion of said fluid-sampling member to the rear of said filtering medium; and

re-monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative of the production capabilities of said earth formation.

16. The method of claim 35 further including the additional step of:

after obtaining said pressure measurements, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation.

17. The method of claim l5 further including the additional steps of:

22 after ob a ning said pressure measurements, reducing the volume of said test chammr again for expelling said second sample into said well bore; reclosing said normally-closed forward end of said fluid-sampling member; and disengaging said fluid-admitting means from said wall surface. id. The method of claim l2 further including the additional steps of:

after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting an other filtered sample of connate fluids from said earth formation; reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore; uncoupling said test chamber from said passage;

reclosing said normally-closed forward end of said fluid-sampling member;

ire-expanding the volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure;

disengaging said fluid-admitting means from said wali surface and urging said fluid-admitting means into sealing engagement with another wall surface of saidwell bore adjacent to another earth formation believed to contain producible connate fluids for isolating said other wall surface from said well bore fluids;

re-opening said normally-closed iorward end of said fluid-sampling member and readmitting said well bore fluids into said fluid passage for again passing said well bore fluids through said filtering medium and said fluid-sampling member into said other earth formation to recleanse said filtering medium and said fluid-sampling member of potentiallyplugging materials;

reclosing communication between said weli bore fluids and said fluid passage;

re-coupling said re-expanded test chamber to said fluid passage at a speed sufficient to quickly induct a second filtered sample of producible connate fluids into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure and displacing loose plugging materials from said other wall surface into said rearward portion oisaidfluid-sampling member to the rear of said filtering medium; and

re-monitoring the pressurein said re-expanded test chamber for obtaining a second series of pressure measurements indicative of the production capabilities of said other earth formation.

19. The method of claim l8 further including the additional steps of:

after obtaining said secondseries of pressure rneasurements, coupling an enclosed sample chamber to said fluid passage downstream for collecting another sample of connate fluids from said other earth formation.

Ed. The method of claim iii further inciuding the ad ditional steps of:

after obtaining said second series of pressure measurements, reducing the volume of said test chamher again for expelling said second sample into said sample-collecting means on said body including a well bore; sample chamber, and means selectively operable uncoupling said test chamber from said fluid passage; for coupling said sample chamber to said fluid passage to receive connate fluids entering said fluidre-closing said normally-closed end of said fluidadmitting means.

sampling member; and 24. The formation-testing apparatus of claim 23 furdisengaging said fluid-admitting means from said ther including:

other wall surface. pressure-measuring means adapted for providing an 21. Formation-testing apparatus adapted for suspenindication of the pressure conditions in fluid sion in a well bore traversing earth formations and passage. comprising: I 2. The formation-testing apparatus of claim 23 fura body having a fluid passage adapted to receive conther including: I

nate fluids; pressure-reducing means on said body inciading an fluid-admitting means on said body including a fluidenclosed test chamber, and means selectively opersampling member having a forward end adapted to able for varying the volume of said test chamber be selectively engaged with a well bore wall for isoincluding piston means movable back and forth belating a portion thereof from well bore fluids, first tween 21 first position reducing the volume of said valve means normally closing said forward end of test chamber and a second position sufficiently exsaid fluid-sampling member, and filtering means pending the volume of said test chamber to reduce coupling said fluid passage to said fluid-sampling the pressure in said test chamber to about atmo member to the rear of said first valve means; spheric pressure; means on said body and selectively operable for posipressure-measuring means adapted for providing intioning said fluid-admitting means against a well dications representative of the pressure conditions bore wall to place said fluid-sampling member in in said test chamber; and communication with earth formations beyond said 25 control means selectively operable after movement well bore wall; and of said piston means to said second position and incontrol means including second-valve means selec eluding third valve means for coupling said test tively coupling said fluid passage to the exterior of chamber to said fluid passage at a speed sufficient said body for discharging well bore fluids through to induct a sample of producible connate fluids said fluid passage and in a reverse direction g from an earth formation in communication with through said filtering means and into an earth forsaid fluid-admitting means into said fluid passage mation to cleanse said filtering means of potentialand said expanded test chamber for momentarily ly-plugging material upon opening of said first reducing the pressure of a connate fluid sample to valve means. about atmospheric pressure. 22. The formation-testing apparatus of claim 21 fur- 26. The formation-testing apparatus of claim25 further including: ther including:

pressure-measuring means adapted for providing an a sample chamber on said body, and fourth valve indication of the pressure conditions in said fluid means selectively operable for coupling said sampassage. ple chamber to said fluid passage to receive con- 23. The formation-testin g apparatus of claim 21 furna'te fluids entering said fluid-sampling member. ther including:

UNITED STATES PATENT OFFICE CE.TEFECATE 0F CORRECTIGN PATENT NO. 3,813,936 DATED 3 June 4, 'NVENTOWS) 1 Harold J. Urbanosky and Frank R. Whitten It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

3 Column 2, line 12, "13" should read a Column 2, line 31, delete "A and B". Column 3, line 28, "borehole" should read The Column 4, line 19, "tublar" should read tubular Column 4, line 36,"2" should read 52 Column 4, line 52, "menas" should read means Q Column 8, line 24, "pressure-actuated" should read imposed Column 8, line 27, delete "23". Column 8, line 44, following "line" insert 96 Column 9, line 42, "systems" should read system Column 10, line 66, "wil" should read will Column 10 line 68, "197" should read 97 9 Column 12, line 15 "wall" should read well Column 14, line 63, "position" should read portion Column 16, line 42, "11'' should read in Column 17, line 31, "saidenclosed" should read said enclosed Column 18, line 3, "sand" should read and Column 19, line 14, "chamber" should read member Column 20, lines 57-58, delete "coupled medium".

Column 20, lines 58-59, delete "said and". Column 21, lines 42-43, delete "said and". Column 22, lines 24-24, delete "said and". Column 22, line 35, "agaln" should read again Sugncd and Scaled this rst a 0 mm 1 D y f June1976 o Arrest:

RUTH C. MACON C. MARSHALL DANN Q Commissioner nfParerm and Trademarks

Claims (26)

1. A method for testing earth formations traversed by a well bore and comprising the steps of: engaging fluid-admitting means coupled by a filtering medium to a fluid passage against a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids for isolating said wall surface from fluids in said well bore and placing said fluid-admitting means in position for receiving connate fluids from said earth formation; discharging said well bore fluids from said fluid passage in a reverse direction through said filtering medium and into said fluid-admitting means and said earth formation for cleansing said filtering medium; and, thereafter, communicating said fluid passage with an enclosed chamber initially at a reduced pressure for drawing producible connate fluids from said earth formation and in the opposite direction through said filtering medium and into said fluid passage to obtain a filtered sample of said connate fluids in said enclosed chamber.

2. The method of claim 1 further including the additional step of: measuring the pressure in saidenclosed chamber and said fluid passage for obtaining at least one pressure measurement indicative of at least one characteristic of said earth formation.

3. The method of claim 1 further including the additional steps of: monitoring at least one characteristic of said filtered sample drawn into said fluid passage for obtaining a series of measurements representative of the production characteristics of said earth formatioN; and, thereafter, discontinuing further communication between said fluid passage and said enclosed chamber for trapping said filtered sample therein.

4. The method of claim 1 further including the additional steps of: monitoring at least one characteristic of said filtered sample drawn into said fluid passage for obtaining a series of measurements representative of the production characteristics of said earth formation; and, thereafter, expelling said filtered sample from said enclosed chamber.

5. A method for testing earth formations traversed by a well bore and comprising the steps of: urging fluid-admitting means including a normally-closed fluid-sampling member coupled by a filtering medium to a fluid passage into sealing engagement with a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids for isolating said wall surface from fluids in said well bore and placing said fluid-sampling member in position for subsequently communicating with said earth formation; opening said fluid-sampling member and admitting said well bore fluids into said fluid passage for passing said well bore fluids through said filtering medium and said fluid-sampling member into said earth formation to cleanse said filtering medium sand said fluid-sampling member of potentially-plugging materials; closing communication between said well bore fluids and said fluid passage; and, thereafter, coupling an enclosed reduced-pressure chamber to said fluid passage for drawing producible connate fluids from said earth formation through said fluid-sampling member and said filtering medium and into said fluid passage to obtain a filtered sample of said connate fluids in said enclosed chamber.

6. The method of claim 5 further including the additional step of: uncoupling said enclosed chamber from said fluid passage for collecting said filtered sample.

7. The method of claim 5 further including the additional steps of: monitoring the pressure in said fluid passage for obtaining a series of pressure measurements representative of the production characteristics of said earth formation; and uncoupling said enclosed chamber from said fluid passage for collecting said filtered sample in said enclosed chamber.

8. The method of claim 5 further including the additional steps of: monitoring the pressure in said fluid passage for obtaining a series of pressure measurements representative of the production characteristics of said earth formation; expelling said filtered sample from said enclosed chamber and uncoupling said enclosed chamber from said fluid passage; reclosing said fluid-sampling member; reducing the pressure in said enclosed chamber; removing said fluid-admitting means from said wall surface and urging said fluid-admitting means into sealing engagement with another wall surface of said well bore adjacent to another earth formation believed to contain producible connate fluids for isolating said other wall surface from said well bore fluids and placing said fluid-sampling member in position for subsequently communicating with said other earth formation; re-opening said fluid-sampling member and re-admitting said well bore fluids into said fluid passage for passing said well bore fluids through said filtering medium and said fluid-sampling member into said other earth formation to recleanse said filtering medium and said fluid-sampling member of potentially-plugging materials; reclosing communication between said well bore fluids and said fluid passage; recoupling said enclosed chamber to said fluid passage for drawing producible connate fluids from said other earth formation through said fluid-sampling member and said filtering medium and into said fluid passage to obtain a filtered sample of said connate fluids from said other earth formation in said enclosed chamber; and remonitoring the pressure in said fluid passage for obtaining a secOnd series of pressure measurements representative of the production characteristics of said other earth formation.

9. The method of claim 5 further including the additional steps of: monitoring the pressure in said fluid passage for obtaining a series of pressure measurements representative of the production characteristics of said earth formation; coupling a sample receiver at a reduced pressure to said fluid passage for collecting filtered connate fluids from said earth formation in said sample receiver; closing said sample receiver for entrapping connate fluids collected therein; expelling said filtered sample from said enclosed chamber and uncoupling said enclosed chamber from said fluid passage; reclosing said fluid-sampling chamber; removing said fluid-admitting means from said wall surface and urging said fluid-admitting means into sealing engagement with another wall surface of said well bore adjacent to another earth formation believed to contain producible connate fluids for isolating said other wall surface from said well bore fluids and placing said fluid-sampling member in position for subsequently communicating with said other earth formation; re-opening said fluid-sampling member and re-admitting said well bore fluids into said fluid passage for passing said well bore fluids through said filtering medium and said fluid-sampling member into said other earth formation to recleanse said filtering medium and said fluid-sampling member of potentially-plugging materials; reclosing communication between said well bore fluids and said fluid passage; recoupling said enclosed chamber to said fluid passage for drawing producible connate fluids from said other earth formation through said fluid-sampling member and said filtering medium and into said fluid passage to obtain a filtered sample of said connate fluids from said other earth formation in said enclosed chamber; and remonitoring the pressure in said fluid passage for obtaining a second series of pressure measurements representative of the production characteristics of said other earth formation.

10. The method of claim 9 further including the additional step of: following the remonitoring step, coupling a second sample receiver at a reduced pressure to said fluid passage for collecting filtered connate fluids from said other earth formation in said second sample receiver; and closing said second sample receiver for entrapping connate fluids collected therein.

11. The method of claim 5 further including the additional steps of: monitoring the pressure in said fluid passage for obtaining a series of pressure measurements representative of the production characteristics of said earth formation; expelling said filtered sample from said enclosed chamber and uncoupling said enclosed chamber from said fluid passage; reclosing said fluid-sampling member; reducing the pressure in said enclosed chamber; removing said fluid-admitting means from said wall surface and urging said fluid-admitting means into sealing engagement with another wall surface of said well bore adjacent to another earth formation believed to contain producible connate fluids for isolating said other wall surface from said well bore fluids and placing said fluid-sampling member in position for subsequently communicating with said other earth formation; re-opening said fluid-sampling member and re-admitting said well bore fluids into said fluid passage for passing said well bore fluids through said filtering medium and said fluid-sampling member into said other earth formation to recleanse said filtering medium and said fluid-sampling member of potentially-plugging materials; reclosing communication between said well bore fluids and said fluid passage; recoupling said enclosed chamber to said fluid passage for drawing producible connate fluids from said other earth formation through said fluid-sampling member and said filtering medium and into said fluid passage to obtain a filtered sample of said connate fluids from said other earth formation in said enclosed chamber; remonitoring the pressure in said fluid passage for obtaining a second series of pressure measurements representative of the production characteristics of said other earth formation; coupling a sample receiver at a reduced pressure to said fluid passage for collecting filtered connate fluids from said other earth formation in said sample receiver; and closing said sample receiver for entrapping connate fluids collected therein.

12. A method for testing earth formations traversed by a well bore and comprising the steps of: urging fluid-admitting means including a fluid passage coupled by a filtering medium to a fluid-sampling member having a normally-closed forward end and a rearward portion to the rear of said filtering medium into sealing engagement with a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids for isolating said wall surface from fluids in said well bore and placing said closed end of said fluid-sampling member into position for subsequently receiving connate fluids from said earth formation; opening said normally-closed forward end of said fluid-sampling member and admitting said well bore fluids into said fluid passage for passing said well bore fluids through said filtering medium and said fluid-sampling member into said earth formation to cleanse said filtering medium and said fluid-sampling member of potentially-plugging materials; closing communication between said well bore fluids and said fluid passage; expanding the volume of an enclosed test chamber coupled to said fluid passage downstream of said filtering medium for reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure; after said test chamber is expanded, coupling said test chamber to said fluid passage at a speed sufficient to quickly induct a filtered sample of producible connate fluids from said earth formation into said expanded test chamber for momentarily reducing the pressure of said connate fluid sample to about atmospheric pressure and displacing loose plugging materials from said wall surface into said rearward portion of said fluid-sampling member to the rear of said filtering medium; and monitoring the pressure in said expanded test chamber for obtaining a series of pressure measurements indicative of the production capabilities of said earth formation.

13. The method of claim 12 further including the additional step of: recording said pressure measurements for obtaining a record representative of the pressure characteristics of said earth formation as connate fluids are produced therefrom.

14. The method of claim 12 further including the additional step of: after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation.

15. The method of claim 12 further including the additional steps of: after the pressure-monitoring step, reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore; uncoupling said test chamber from said fluid passage; reclosing said normally-closed forward end of said fluid-sampling member; re-opening said normally-closed forward end of said fluid-sampling member and re-admitting said well bore fluids into said fluid passage for again passing said well bore fluids through said filtering medium and said fluid-sampling member into said earth formation to recleanse said filtering medium and said fluid-sampling member for potentially-plugging materials; reclosing communication between said well bore fluids and said fluid passage; re-expanding the volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospHeric pressure; after said test chamber is re-expanded, re-coupling said re-expanded test chamber to said fluid passage at a speed sufficient to quickly induct a second filtered sample of producible connate fluids into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure and displacing additional loose plugging materials from said wall surface into said rearward portion of said fluid-sampling member to the rear of said filtering medium; and re-monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative of the production capabilities of said earth formation.

16. The method of claim 15 further including the additional step of: after obtaining said pressure measurements, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation.

17. The method of claim 15 further including the additional steps of: after obtaining said pressure measurements, reducing the volume of said test chamber again for expelling said second sample into said well bore; reclosing said normally-closed forward end of said fluid-sampling member; and disengaging said fluid-admitting means from said wall surface.

18. The method of claim 12 further including the additional steps of: after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation; reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore; uncoupling said test chamber from said fluid passage; reclosing said normally-closed forward end of said fluid-sampling member; re-expanding the volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure; disengaging said fluid-admitting means from said wall surface and urging said fluid-admitting means into sealing engagement with another wall surface of said well bore adjacent to another earth formation believed to contain producible connate fluids for isolating said other wall surface from said well bore fluids; re-opening said normally-closed forward end of said fluid-sampling member and re-admitting said well bore fluids into said fluid passage for aga1n passing said well bore fluids through said filtering medium and said fluid-sampling member into said other earth formation to recleanse said filtering medium and said fluid-sampling member of potentially-plugging materials; reclosing communication between said well bore fluids and said fluid passage; re-coupling said re-expanded test chamber to said fluid passage at a speed sufficient to quickly induct a second filtered sample of producible connate fluids into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure and displacing loose plugging materials from said other wall surface into said rearward portion of said fluid-sampling member to the rear of said filtering medium; and re-monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative of the production capabilities of said other earth formation.

19. The method of claim 18 further including the additional steps of: after obtaining said second series of pressure measurements, coupling an enclosed sample chamber to said fluid passage downstream for collecting another sample of connate fluids from said other earth formation.

20. The method of claim 18 further including the additional steps of: after obtaining said second series of pressure measurements, reducing the volume of said test chamber again for expelling said second sample into said well bore; uncoUpling said test chamber from said fluid passage; re-closing said normally-closed end of said fluid-sampling member; and disengaging said fluid-admitting means from said other wall surface.

21. Formation-testing apparatus adapted for suspension in a well bore traversing earth formations and comprising: a body having a fluid passage adapted to receive connate fluids; fluid-admitting means on said body including a fluid-sampling member having a forward end adapted to be selectively engaged with a well bore wall for isolating a portion thereof from well bore fluids, first valve means normally closing said forward end of said fluid-sampling member, and filtering means coupling said fluid passage to said fluid-sampling member to the rear of said first valve means; means on said body and selectively operable for positioning said fluid-admitting means against a well bore wall to place said fluid-sampling member in communication with earth formations beyond said well bore wall; and control means including second valve means selectively coupling said fluid passage to the exterior of said body for discharging well bore fluids through said fluid passage and in a reverse direction through said filtering means and into an earth formation to cleanse said filtering means of potentially-plugging material upon opening of said first valve means.

22. The formation-testing apparatus of claim 21 further including: pressure-measuring means adapted for providing an indication of the pressure conditions in said fluid passage.

23. The formation-testing apparatus of claim 21 further including: sample-collecting means on said body including a sample chamber, and means selectively operable for coupling said sample chamber to said fluid passage to receive connate fluids entering said fluid-admitting means.

24. The formation-testing apparatus of claim 23 further including: pressure-measuring means adapted for providing an indication of the pressure conditions in said fluid passage.

25. The formation-testing apparatus of claim 21 further including: pressure-reducing means on said body including an enclosed test chamber, and means selectively operable for varying the volume of said test chamber including piston means movable back and forth between a first position reducing the volume of said test chamber and a second position sufficiently expanding the volume of said test chamber to reduce the pressure in said test chamber to about atmospheric pressure; pressure-measuring means adapted for providing indications representative of the pressure conditions in said test chamber; and control means selectively operable after movement of said piston means to said second position and including third valve means for coupling said test chamber to said fluid passage at a speed sufficient to induct a sample of producible connate fluids from an earth formation in communication with said fluid-admitting means into said fluid passage and said expanded test chamber for momentarily reducing the pressure of a connate fluid sample to about atmospheric pressure.

26. The formation-testing apparatus of claim 25 further including: a sample chamber on said body, and fourth valve means selectively operable for coupling said sample chamber to said fluid passage to receive connate fluids entering said fluid-sampling member.

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