US2581070A - Formation tester - Google Patents

Description

2 sr-xEETs-SHEET 2 4 i ooo n ma@ i w vwz 462/2 A@ :FM ........,..\F /7 y 3 4 ,J f ca ...1 m f... 5 1 q 4r ..wN..vak. JL A `J.I.....r.J\ /...\H.l.\.. 5 JL Jan. 1, 1952 Filed Feb. 6, 1948 Qobcr-b H. @Lood Sovenov Patented `an. 14, 1952 OFFICE FORMATION TESTER Robert H; Blood, Tulsa, Okla., assignor to Stand? ard Oil Development Company, a corporation of Delaware Application February 6, 1948, Serial No. 6,780

This invention relates to improved apparatus for the testing of formations through which a hole is drilled to determine possible oil bearing strata. In particular the invention concerns a means which may be inflated to seal olf a desired portion of a well and permeable means associated therewith through which fluid samples may beV withdrawn from the desired portion of the well.

In conventional oil drilling operations, drilling devices arev used to bore a hole in the earth. During drillingthe hole is generally flooded with drilling mud which .creates sufficient hydrostatic pressure toprevent the ow of any fluids from formations which are drilled.` It is frequently desirable to periodically seal oil" the well and to reduce the hydrostatic pressure on the well suflciently to Venable samples of the fluids existing in the well to be brought to the surface. The present invention is concerned with an improved apparatus for sealing off the well and for withdrawing a portion of the fluid as desired. This operation is called formation testing. Formation testing gives valuable information as to whether or not oil production may be expected from the formation tested. Information will be given relative to the possible productivity of the well, the pressure'of the oil, and the ratio of gas to oil.

Oil bearing formations generally occur in permeable zones positioned below an impermeable zone in the earth. It is generally desired therefore to seal off the well immediately below the impermeable zone in such a manner that the hydrostatic pressure of the drilling mud maintained in the well may be decreased suiciently to permit withdrawinga sample of the fluid existing below the impermeable layer and so that the 'sample of fluid may be brought to the surface. In accordance with the present invention a balloon type packenwhich may be inflated, is suspended in the well at the point it is desired to test the formation. On suitably inating this packer the well may be completely sealed off at the desired point so that the hydrostatic head above the seal may be reduced. A permeable membrane associated with the inflated packer permits withdrawal of fluids from theformation. The reduction of the hydrostatic head above the inflated packer permits the ud flowing through 'the membrane to flow upwardly through, the drilling string to the surface of the earth.

My invention will be more fully understood from the following detailed description. in conmeable rubber or s claims. (o1. 16e-40) nection with the accompanying drawings in which:

Figure I represents an embodiment of my in.-

vention in the deflated position` adapted for sampling a formation which is not'at the bottomj= of the hole being drilled;

Figure II represents the same apparatusl injthe.- inflated position suitable for rwithdrawing the desired sample;

Figure III represents an embodiment ofi'my-y invention in the deflated position which is adapted for sampling a formation at the bottom off.'

a drilled hole and;

Figure IV representsthe embodiment ofFigurel III in the inated position adapted for with'- drawing the desired sample.

Referring now to Figure I, the'numeral I designates a metallic structure which is suitablyconnected to thedrilling pipe orl string 2. Thedrilling string is generally connected in 30 foot sections and extends upwardly to the surface of theV earth. The structure l is partially drilled out at its upper end to providea cavity llhaving l are a'pair of concentrically positioned elastic. bags 6` and 26 deningbetween them an annular chamber 28. These bagsaresuitablyr sealed atv the lower end to a rod l, attached to orintegral with the structure l, and extendingdownwardly through the elastic bag 26. The elastic bagsare conveniently composed of rubber, although'it-is to be understood other materialsmay be used such as impermeable cloth or fabric. The'bags are so attached to the structure l'Y thatv they'are separated by permeable plug 8l at the juncture with structure l.

may be metallic in nature. Provision of this permeable plug permits a flow ofy fluid froml inside chamber 28, through the permeable plug 8, into the passageway 3; which is controlled by check valve 9. Thisvalve ls-'so connected as to permit a flow by a similar check valveA Ill; This valve is'adapted to permit the flow ofv lluidfromA the cavity Ilto chamber 24' in-theelastic bagwhile prevent'-v This plug may consist of per#` of uidupwardly: from` the bag but so as to prevent the flow of` l, downwardly to chamber -24l within elastic bag 26, is controlled 3 ing the flow of fluid in the reverse direction. This valve may be called the inflation valve.

The passageway 5 connects the cavity I1 to the external portion of the well around the structure l. A check valve H controls the flow of fluid through this passageway so as to permit flow from the cavity I1 to the wel.

Contained within the annular chamber 28 formed by the elastic bags s and mare a multitude of pellets l2. These may consist of glass beads, metal balls, or equivalent packing. The pellets l2 are maintained throughout the chamber by means of separating partitions I3, I4, i5, and i6. These partitions branes such as permeable rubber, adapted to prevent the passage of the packing material l2, from one compartment to another while permitting the flow of fluid through the diierent compartments. Circumferentially extending around the wall of the bag 6, approximately midway between the top and the bottom of the bag, is a permeable membrane 2l. This membrane may consist of permeable rubber, for example, or if desired may consist of a fine mesh metallic screen. This-section of the bag is anV integral part of the wall of bag 6. It will be noted that a comparatively small circumference o the bag is provided with the permeable material 2|.

In operating the embodiment shown in Figure I, after a suitable hole has been drilled, the device shownis lowered intol the Well attached to the bottom ofy a drill string. Y The device is lowered to the point at which it is desired to test for possible oil production, which may have been determined by well-logging or equivalent procedures carried out during the drilling proce-dure. In Figure I it is assumed that a possible production consist of permeable mem- I zone, permeable stratum 20, exists adjacent to the permeable membrane 2| of the bag. The bag 26 is then inflated to the position shown in Figure II by pumping drilling mud or other iluid through the drill string, through the cavity I1 of the structure I, and through the passageway 4 into chamber 24 of the fiexible bag. During this operation, valve 9 prevents floWof the mud into annular chamber 28 and valve il is likewise closed. This is effective incausing the bag to inflate as in Figure 2, completely sealing the hole along the expanded circumference of the bag. When the pressure of the drilling mud pumped within the bag reaches a predetermined level, determined by the toughness of the bag, further expansion is limited by the opening of the by-pass valve ll, which serves to 'by-pass the iiow of drilling mud into the external portion of the well. This may be accomplished by suitably adjusting the force of the spring 25 in the valve l I, so that the drilling mud will be by-passed when the bag has been inflatedto a desired pressure. When mud has been pumped intothe 'drilling lstem sufficiently long so that the bagl will have been completely inflated and some by-passing of the mud will have occurred, pumping may be discontinued causing the valves l0 and Il to close, completely sealing the drilling mud in the expanded bag. Thereafter,

pressure may be relieved from the fluid contained in the drilling string so that the hydrostatic head in the drilling stem is lower than the pressure existing in the formation 2|) to be tested. Suitable decrease in the hydrostatic pressure existing in the drilling string` may be achieved simply by discontinuing the pumping 4of fluid through the string and by applying a pump to withdraw fluid from the* drilling string. Whenthis has been achieved, iiuidsfrom theproduction zone 20 will permeate the membrane 2l', flowing within the annular chamber 28. The pressure differential will cause the fluid to flow upwardly through the annular chamber and through the. production valve 9, into the cavity of the structure I, and upward through the drilling string. By this means a sample of the iiuid existing in the zone 2U, may be withdrawn and passed to the surface of the earth. It will be noted that the packing material l2 is effective during this portion of the operation to prevent the sealing of the annular chamber between the bags by virtue of the pressure of the drilling mud within the bag 26. After a suitable sample has been withdrawn from the formation to be tested, the bag may be deflated by dropping a suitable tripping device into the drill string. As illustrated in Figure I, the tripping device 30 may consist of a cylindrical metallic object having an extending lug 3l at its lowermost end. This lug is adapted to press against the valve I0 so as to permit flow of uid through the passageway 4 upwardly into the drilling stem.Y Suitable corrugations along the contact surface of the tripping device 30 may be employed to permit the ow of fluid between the tripping device and the structure l. By thismeans the valve I0 is opened permitting the flow of drilling mud from the inside of the bag 26, causing deflation of the bag. The entire device may then be withdrawn from the well and drilling operations may be resumed. It is to be noted that in the embodiment shown in Figures I and II the formation to be'v tested is not at the bottom of the well. Consequently on sealing off the upper part of the wellV a considerable pressure differential could developV above and below the sealing bag. This could be caused for example by the loss oi drilling mud below the tester into an adjacent formation. A conduit 35 is provided through the rod 'l providing a passageway to permit equalization of this pressure. f

A further embodiment of my invention is illustrated in Figures III and IV. The embodiment illustrated is particularly adapted for the4 testing of a formation located at the bottom of a drilled hole. InFigures III and IV, parts similar to those of Figures I and II areV identiiied by similar numerals. The apparatus illus-- trated may be fully understood by reference to the foregoing description of the apparatus shownA in Figures I and II. It will be Anoted that in order to test a formation at the bottom of the hole. theV permeable portion 2l of bag 6 ispositioned at the bottom of the bagrather than midway up the bag. Consequently, it is not necessary that the outer bag 6 extend over the entire length of lbag 26, it onlybeing necessary that the lower portion of the packer have an annular chamber 28. When the bag has been inflated, `according to *ther procedure described,

and when the hydrostatic pressure in the drilling string has been suitably decreased, -fluid samples flowing from the formation 20 will en-V ter the annular chamber 28 through the porousv membrane 2l. The uid may then flow through the permeable plug 8, which in this embodiment is a circular ring, and may then enter the passageway 31` through the connecting passageway 45, and thence to the surface through valve 9, chamber 3 and the drill string. Since the formation tester in this case is positioned at the bottom of the drill hole, it is not necessary to provide meansfor equalizing the pressure above and-below the elastic packer. Consequently, it is not necessary to have the equivalent of pas-t sage 35 in Figure I, in the embodiment of Figures III and IV.

As described my invention comprises a packer consisting of a pair of concentrically positioned elastic bags, adapted to be lowered into a drill hole. A portion of the Wall of the outer elastic bag consists of a porous membrane permitting a now of iluid through the membrane to the annular chamber dened by the two bags. The bags are suitably attached to a supporting member, and a permeable plug is positioned in the termination of the annular chamber so that the uid may ow through this permeable plug into chambers provided to conduct the uid into the drilling string and to the surface of the earth. While my invention has been described in connection with drill pipe, it is to be understood that it may readily be adapted to wire-line devices as well. It is apparent many other modications of the apparatus described may be The appended claims are, therefore, to be given a broad interpretation commensurate to the contribution to the prior art.

Having now described my` invention, I claim:

1. Apparatus for use in testing a borehole to determine the presence of possible oil bearing formations which comprises supporting means adapted to be connected to a drill string, a pair ber, a permeable membrane comprising a portion of the wall of the outer of said pair of elastic bags, a conduit connecting the interior of the drill string with the interior of the inner of said pair of elastic bags, said conduit having a valve permitting the ilow of uid from the interior of the drill string to the interior of said inner elastic bag and preventing uid ow in the op- CTI posite direction, and a conduit connecting the interior of the drill string with said annular chamber, said last named conduit having a valve permitting I'low of uid from said annular chamber to the interior of the drill string and preventing uid ow in the opposite direction.

2. The apparatus defined by claim 1 including a conduit' connecting the interior of the drill string with the exterior thereof through a valve permitting flow of fluid outwardly into the borehole from the interior of the drill string when a predetermined fluid pressure is attained withf in the drill string.

3. Apparatus according to claim 1 including a plurality of permeable separating partitions disposed within said annular chamber and defining separate compartments for said packing material.

6. The apparatus defined by claim 1 in which the elastic bags are constructed of rubber.

ROBERT H. BLOOD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS

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