US2703055A - Diaphragm-type mud pump - Google Patents

Description

March l, 1955 J, VETHl ET AL 2,703,055

` DIAPHRAGM-TYPE MUD PUMP Filed July l1, 1951 2 Sheets-Sheet l lnveni'ors'- J. Vei'h W. J. van Heeokeren l:Their Aforneg March 1, 1955 J. VETH ETAL 2,703,055

DIAPHRAGM-TYPE MUD PUMP Filed July 1l, 1951 2 Sheets-Sheet 2 Inveni'or'- l Vei'h Ffa' Z WJ. von Heeckeren Their A'orneg DIAPHRAGM-TYPE MUD PUMP Jan Veth and Willem Jan Van Heeckeren, Delft, Netherlands, assignors to Shell Development Company, Emeryville, Calif., a corporation of Delaware Application July 11, 1951, Serial No. 236,136 Claims priority, application Netherlands July 21, 1950 7 Claims. (Cl. 103-152) This invention relates to pump installations and pertains more particularly to a system for pumping and circulating a corrosive liquid or a liquid containing appreciable quantities of an abrasive material such, for example, as a well drilling iluid.

During the drilling of Wells by the rotary method, a drilling mud which commonly contains clay or a solid weighting material is circulated down a string of drill pipe and up around said pipe to carry the bit cuttings to the surface. While most of the cuttings are removed from the mud by screens or settling pits, complete removal of the cuttings is never effected. Consequently, the mud pumps are required to handle fluid containing a considerable amount of abrasive material, resulting in rapid wear of the pump parts.

In order to overcome the abrasive action of the mud, diaphragm pumps have been used which employ an auxiliary or motive liquid which serves to impart the necessary pressure and displacement action to the mud to be pumped by means of a diaphragm. In this type of a pumping installation, the` auxiliary liquid compartments of two diaphragm displacers or accumulators are connected by means of a change-over device or a reversing valve to the suction and pressure sides of an auxiliary liquid pump in such a way that the auxiliary liquid is alternately pumped into or drawn out of the compartments as the mud is pumped out of or drawn into the compartments on the other side of the diaphragms.

At the end of each stroke all the mud in one diaphragm displacer is forced therefrom yby the auxiliary-Huidactuated diaphragm therein While the other diaphragm displacer has been filled with drilling mud. It will be seen that the greatest drawback to this type of a pumping installation is that there is substantially no ilow of mud from either diaphragm displacer at the end of each stroke or displacement of the diaphragms.

It is therefore the primary object of the present invention to provide a pumping installation wherein the output (volume per unit of time) of the liquid being pumped is maintained at a substantially constant value.

It is also an object of this invention to provide a pumping installation adapted to pump a liquid containing substantial amounts of an abrasive material which normally causes considerable wear to various parts of conventional pumps.

It is also an object of the present invention to provide a light Weight mud pump which may be readily transported from one drilling location to another.

A further object of this invention is to provide a highpressure high-capacity mud pump capable of circulating a weighted drilling mud in deep (say, 20,000 ft.) Well drilling operations.

These and other objects of this invention will be understood from the following description of the invention as shown in the accompanying drawing, wherein:

Figure 1 is a diagrammatic View of the present pumping installation, including a suitable piping arrangement for connecting the installation to a well head and a mud pit.

Figure 2 is a cross-sectional view of a change-over device or reversing valve incorporated in the present pumping installation.

Figure 3 is a cross-sectional view of a diaphragm displacer or accumulator of the present invention.

Figure ,4, is a cross-sectional view of a slide valve mounted atop of the diaphragm displacers for controlling K N United States Patent O Patented Mar. 1, 1955 ice the iiow of a pressure liuid to the change-over device of the present invention.

It has been found that drilling operations may be carried out more eiciently if the ow of drilling mud from the mud pump is kept at a substantially constant value. In .Order for a dual diaphragm pump installation to produce a substantially constant output, it is necessary for the diaphragms of said pumps to work together in such a manner that each takes over, as gradually as possible, the others function of discharging the mud into a common ow line.

The uniformity of liquid delivery by a pump installation utilizing an auxiliary or power liquid depends in the first place, assuming a uniform discharge by the auxiliary liquid pump, on the correct functioning of a change-over device, the reversing of which causes a suction displacer to become a pressure displacer, and vice versa. When employing two displacers there must be no hiatus between the pressure period of the one and that of the other; in other words, one period must follow directly upon the other or gradually merge into the other. This has been achieved in the present pumping installation by ensuring that the output of one displacer gradually decreases towards the end of its pressure period, While the other displacer begins its delivery at an increasing rate, so that the joint output during this transition period is substantially equal to that of one displacer during the remaining part of its pressure period. Thus, since the suction period of a displacer is shorter than the pressure period, the suction capacity of the pumping apparatus for the auxiliary liquid should preferably be greater than its pressure capacity. The pumping apparatus can, therefore, consist of a suction and force pump, the latter having a smaller capacity than the former. It is preferable to choose a rotary type for these pumps, for example, centrifugal or screw pumps, which combine light Weight with a uniform output. These pumps may preferably be installed in an open circuit for the auxiliary liquid, viz. a circuit having a reservoir from which the force pump withdraws its fluid and into which the suction pump delivers its liquid. The quantity of liquid in this reservoir can vary in connection with, for instance, expansion due to temperature increases. Hence, factors such as changes in temperature of the mud, etc., have no adverse effects on the installation according to the invention, but are completely absorbed by the reservoir. The liquid level in the reservoir can, at the same time, give an indication regarding leaks in the circuit of the auxiliary liquid such as might arise as a result of cracks in a pump diaphragm, as such leaks will alter the quantity of liquid in the circuit of the auxiliary liquid.

For the most eicient operation of the installation it over device of the present invention is regulated auto` matically, depending on the position of the diaphragms in the diaphragm displacers. Since an auxiliary liquid under pressure is used in the present installation, hydraulic controls for operating the change-over device are employed, although these controls may also be mechanical, electrical or pneumatic.

It is important that the diaphragms should not be excessively burdened by too great a difference between the pressures prevailing on either side of them. This danger presents itself particularly at the end of the stroke of a diaphragm, as a continued supply or discharge of auxiliary liquid might then cause undesirable deformation to occur. In order to prevent this with certainty, the present pump provides that, at the end of a stroke, the chamber within the displacer casing which has the minimum volume is shut off from the line or lines connected thereto. At the end of the suction stroke, it is the charnber for the auxiliary liquid which is thus shut ci from the suction line for the auxiliary liquid, so that no more auxiliary liquid can be draw from the displacer casing. At the end of the pressure stroke, the pressure chamber for the mud ilush is shut olf. Should further auxiliary liquid be fed to the displacer and the pressure in the auxiliary liquid chamber rise as a result of this, this pressure would be transmitted by the diaphragm to the mud fluid chamber, so that the diaphragm is exposed only to unimportant pressure differences. The shutting Volf of the said chambers of the displacer casing can be effected in a simple manner by means of valves fitted to the diaphragms which are arranged to seat in and close the uid ports to the relevant chambers.

Referring to Figure l of the drawing, the present mud pumping installation comprises two spherically constructed displacer casings 1 and 1', each of which contains a diaphragm 2, 2', attached at its circumference tothe displacer casing along a median circle thereof. In the drawing, each of the diaphragms is illustrated as being near one of its end or flexed positions, diaphragm 2 having just completed its suction stroke while diaphragm 2' approaches the end of its pressure stroke. The chambers 51 and 51 situated under the diaphragms in the displacer casings are for the mud iiush. The mud is sucked from a reservoir 3 via a conduit or line 4, the lines 5 and S', the suction valves 6 and 6, and the lines 7 and 7', which last are connected to the lowest point of the displacer casings 1 and 1'. The mud iiush under pressure coming from the displacers is discharged via the lines 7, 7', the pressure valves 8, 8', the lines 9, 9' and the line 10, to which an air chamber 11 may be tted if necessary. The line leads to a well borehole (not shown), from which the line 50 feeds the mud ilush back to the reservoir 3. The suction and delivery valves 6, 6' and 8, 8' are of normal construction.

The chambers 52 and 52 located above the diaphragms inthe displacer casings are intended for the auxiliary liquid, which, for instance, may be a suitable oil. The circuit for the auxiliary liquid consists of two pumps, viz., a suction pump 12 and a force pump 13, a reservoir 14, a change-over device and the necessary conduits or lines connecting these parts. While the suction pump 12 is normally sutiicient to iill the displacers 1 and 1' with mud, an auxiliary booster pump 56 may be positioned in the suction line 4 from the rnud pit 3, if desired. In the position of the change-over device 15 shown in Figure 1, the displacer 1 is connected to the delivery side of the pump 13 and the displacer 1 to the suction side of the pump 12. The force pump 13 withdraws auxiliary liquid from the reservoir 14 via a line 16 and pipes it under pressure via a line 17 to the change-over device 15, whence the liquid is fed to the displacer 1' via line 18. At the suction stroke of the displacer 1 (shown completed in the drawing) the auxiliary liquid is withdrawn from this displacer through the line 18, the change-over device 15 and the line 19 by the pump 12, which pump discharges the auxiliary liquid through the line 20 to the reservoir 14.

The change-over device 15 is constructed as a cylinder with a piston valve 21 movable therein. In Figure 1 of the drawing this valve is shown in its extreme right position; when it is in its left hand position the displacer 1 is connected through line 18 and valve 15 to the line 17 of the force pump and the displacer 1' is connected through line 18' and device 15 to the line 19 of the suction pump 12. The piston valve 21 is connected to a piston 22, which lies inside a cylinder 23 and is actuated by means of pressure fluid which can be supplied on either side of the piston 22 to the cylinder 23 in a manner which will be described in more detail hereinbelow.

The construction of the change-over device 15 is shown in greater detail in Figure 2. To a casing 24 are connected the lines 18 and 18' which lead to the displacers, line 17 for the pressure liquid originating from the force pump, and the manifold line 19 whose other end is connected to the suction side of the suction pump. A divided or split cylinder lining 25 is fitted inside the casing 24 and is provided with ports 26 and 26' communicating with lines 18 and 18', a port 27 communicating with line 17, and ports 28 and 28' communicating with line 19. The piston valve itself comprises two pistons 29 and 30 which are mounted on a rod having portions 21 and 31.

When the piston valve is in the position shown in Figure 2, lines 1.7 and 18 are in communication with each other as are also lines 19 and 18'. At this position, therefore, auxiliary liquid is fed under pressure to the displacer 1 and is drawn off from the displacer 1'. The ports in the cylinder lining 25 and the pistons 29 and 30 on the rod 31 are preferably located so that the distance between the pistons 29 and 30 is at least equal tothe distance between the ports 26 and 26'. Thus, when the pistonvalve 21 is moved (from its position shown in Fig. 2) to the right for the change-over of the displacers, the

. most position by means of a little ball 40 under spring' piston 30 begins to open the port 26' at the momentat" which piston 29 begins to close the port 26, and this latter port is only completely 'closed at the moment at which port 26 is fully open. Accordingly, between the two given extreme positions of the piston valve 21, auxiliary liquid is fed under pressure into both the displacer 1 and the displacer 1', to the first at a gradually decreasing, and to the second at a gradually increasing rate.

Concurrent with this action, the output of mud flush discharged by the displacer 1 also gradually decreases and that of the displacer 1" gradually increases so that the function of discharging drilling mud ush is gradually taken over by one displacer from the other. As the output of pressure liquid from the pumping apparatus is substantially constant, the output of mud flush under pressure is also constant. In Figure 2, a servomotor housing 23, is shown on the right side of the casing 24 which houses the change-over device 15. A piston 22 is mounted on the piston rod 31 which extends into the housing 23. Lines 32 and 32 are connected to the two extremities of the housing 23 so that servicing liquid can be fed to and discharged from these extremities. The manner in which this is carried out will be explained with reference to' Figure l.

The lines 32, 32' connect the servomotor housing 23 with the distribution valve mechanisms 33, 33' which are built yon the displacers 1 and 1' and are formed by cylinders in which movable distribution valves 34 or 34 (see Figure 4) are positioned. Each distribution mechanism is connected to a line 35 or 35', which line is in communication with the delivery line 17 of the force pump 13, and to a discharge line 36 or 36 which leads to the reservoir 14. The pressure liquid necessary to actuate the servomotor piston 22 is thus withdrawn from the 'circuit of the auxiliary liquid. The distributing slide valves 34, 34 are controlled by the movement of the diaphragms 2, 2 by through rods 37, 37' which are attached to the diaphragms. The rods are fitted with stops 38, 39 and 38', 39', respectively. Each time one of the diaphragms approaches one of its extreme end positions or, in other words, nears the end of its stroke, one of the distributing slide valves is moved by one of these stops.

Accordingly, in Figure 1, the distributing slide valve 34' has reached a position in which lines 32' and 35 are brought into communication with each other and pressure liquid is thus admitted to the right side of the servomotor piston 22. The other distribution slide valve 34 is now in its highest position and thereby connects the linesk 32 and 36 with each other, so that the liquid on the left side of the servomotor piston 22 escapes to the reservoir 14. The change-over device 15 is therefore now in its change-position.

It is worthy of note that this change-over can only take place when the two distributing slide valves 34 and 34' have been actuated by the diaphragms. As already stated above, the pressure stroke of a displacer is of longer duration than the suction stroke, since the pressure strokes of both displacers must partially overlap each other. The diaphragm 2 will therefore reach the end of its 'suction stroke before the membrane 2' reaches the end of its pressure stroke, and will therefore actuate the distributing slide valve 34 before diaphragm 2' actuates distributing slide' valve 34'. When distributing slide valve 34 has already been actuated, the diaphragm 2' continues its pressure stroke for a moment until the distributing slide valve 34' has also been moved and the change-over mechanism cango into action. As previously explained, during this change-over diaphragm 2' will, further continue its pressure period for a moment after diaphragm 2 has already begun its period of pressure.

One type of distributing slide valves is shown in greater detail in Figure 4. In this figure, 33 is the cylinder for the sliding valve, 34 the valve, 32 the line leading to the servomotor cylinder, 35 the line for the pressure liquid, 36 the discharge line,y 37 the rod attached to the diaphragm and 38 and 39 are the stops attached to this rod. The distributing slide valve 34 is held in its upperpressure, which is pressed into a grooye 41 of the cylinder 33. The distributing slide valve 34 is held in its lowest position by means of an annular disc 42 on which the distributing slide valve 34 can rest.

Figure 3 shows, in greater detail, a displacer with the casing 1 divided into two hollow hemispheres and the diaphragm 2 clamped by its edge between these two parts.

In addition to the rod 37, which actuates the distributing slide valve 34 (Fig. 4), the diaphragm also has a valve disc 43, 44 on either side. The outlet ports from the displacer casing 1 to lines 18 and 7 are so constructed as to serve as seats for the valve discs 43 and 44, respectively. When the diaphragm 2 has moved as far as possible in one of its prescribed directions, one of the chambers into which it divides the displacer casing is shut olf from the line connected to this chamber. In Figure 3 the uppermost chamber 52 is thus separated from the line 18. Accordingly, any decrease in pressure in this line cannot be transmitted to the uppermost chamber of the displacer casing and the diaphragm is thereby safeguarded from too great differences in pressure. When the diaphragm is in its lowest position the valve disc 44 shuts off the line 7. A continued supply of pressure liquid to the upper surface of the diaphragm can bring about increased pressure above the diaphragm, but this pressure is transmitted through the diaphragm to the chamber beneath the diaphragm, so that a notable difference in pressure between the two chambers cannot arise and the diaphragm is protected against overloading which might lead to the formation of cracks.

The apparatus may be tted with the necessary indicators and safety devices, such as safety and overflow valves 53 and 54 which operate when the desired pressures are exceeded or not attained.A It is of particular importance to be able to recognize quickly any signs of leakage in the diaphragms, for a leaking diaphragm would permit the penetration of mud flush into the circuit for the auxiliary liquid, oil for example, and cause damage to, or excessive wear of the pumps and regulating devices included in this circuit. An indication of the presence of such a leak can readily be found in the liquid level of the tank 14, as a leak would cause an increase or decrease in the quantity of liquid in the auxiliary liquid circuit and thus alter the level in the tank 14. Any suitable device, for example a float 55, which reacts to this level, can therefore be used as a level indicator. Another, quicker method of detecting the presence of mud flush in the auxiliary liquid circuit can be found, for instance, in indicators 45, 45 which may be incorporated in the lines 1S, 18 and can react to the electric conductivity or the di-electric constant of the liquid passing through the lines 18, 18', which liquid, as already stated, is normally oil.

The various parts of the installation, such as the displacers, change-over and control devices, can, of course, be constructed in other ways. Furthermore, instead of only two displacers a greater number may be provided. Although the present pumping installation has been described for purposes of illustration with regard to its use in pumping abrasive drilling muds, it is understood that the subject pumping installation may also be employed for pumping corrosive or abrasive fluids, or fluids of any other type which have a deleterious effect on the working elements of pumps.

We claim as our invention:

1. In an apparatus for pumping an abrasive fluid, a reservoir containing a non-abrasive driving fluid, a reservoir containing an abrasive fluid, at least two pump chambers formed in said apparatus, a flexible diaphragm separating each of said chambers into two compartments containing the driving fluid and the abrasive fluid respectively, a force pump, a suction pump, conduits connecting each of said pumps with said driving fluid reservoir, conduit means connecting the driving fluid compartment of each of said pump chambers with said pumps, valve means in said conduit means for controlling the flow of driving fluid between the reservoir and said chambers and thereby causing displacements of said diaphragms in one direction and then the other, said valve means comprising a valve housing having port means in communication with said conduit means, piston means slidable within said valve housing from one end to the other, opening and closing said port means, said conduit means to both of said pump chambers being opened when said piston means is in an intermediate position of travel within said housing, transmission means operatively connected and responsive to the movement of said diaphragms for selectively actuating said valve means so as to cause a simultaneous discharge of driving fluid into the respective compartments of said pump chambers over a portion of the discharge stroke of said diaphragms, and intake and discharge conduit means in communication with said abrasive flu1d compartments of said pump chambers.

2. An apparatus for pumping an abrasive drilling fluid` comprising at least two pump chambers formed in said apparatus, a flexible diaphragm dividing each of said chambers into two compartments adapted to contain a driving fluid and an abrasive fluid respectively, a force pump, a suction pump, conduits connecting each of said pumps with a reservoir of driving fluid, conduit means connecting the driving fluid compartment of each of said pump chambers with said pumps, valve means in said conduit means for controllingthe flow of driving fluid between the reservoir and said chambers thereby causing displacements of said diaphragms in one direction and then the other, said valve means comprising a valve housing having port means in communication with said conduit means, piston means slidable within said valve housing from one end to the other, opening and closing said port means, said conduit means to both of said pump chambers being opened when said piston means is in an intermediate position of travel within said housing, transmission means operatively connected to said valve means so as to cause a simultaneous discharge of driving fluid into the respective compartments of said pump chambers over a portion of the discharge stroke of said diaphragms, conduit means connecting the abrasive fluid compartments of said pump chambers with an abrasive fluid reservoir and a well borehole, and valve means in said abrasive fluid conduit means for alternately connecting said pump chambers to said abrasive fluid reservoir and then said well borehole.

3. An apparatus for pumping an abrasive drilling fluid,` L

comprising a reservoir of a non-abrasive driving fluid, a reservoir of drilling fluid, at least two pump chambers formed in said apparatus, a flexible diaphragm separating each of said chambers into two compartments containing the driving fluid and the drilling fluid respectively, a force pump, a suction pump, conduit means connecting each of said pumps with said reservoir of driving fluid, a system of conduits connecting the driving fluid compartment of each of said pump chambers with said pumps, valve means in said system of conduits for controlling the flow of driving fluid between the reservoir and said chambers and thereby causing displacements of said diaphragms in one direction and then the other, said valve means comprising a valve housing having port means in communication with said conduit means, piston means slidable within said Valve housing from one end to the other, opening and closing said port means, said conduit means to both of said pump chambers being opened when said piston means is in an intermediate position of travel within said housing, linkage means affixed to said diaphragms and movable therewith so as to cause a simultaneous discharge of driving fluid into the respective compartments of said pump chambers over a portion of the discharge stroke of said diaphragms, conduit means connecting the drilling fluid compartments of said pump chambers with the drilling fluid reservoir and a well borehole, valve means in said drilling fluid conduit means for alternately connecting said pump chambers with said reservoir and said well borehole, and a second force pump in said conduit means between the drilling fluid compartments and reservoir for charging the pump chambers with drilling fluid.

4. An apparatus for pumping an abrasive drilling fluid, comprising a reservoir of a non-abrasive driving fluid, a reservoir of drilling fluid, two pump chambers formed in said apparatus, a flexible diaphragm separating each of said chambers into two compartments containing the driving lluid and the drilling fluid respectively, a force pump, a suction pump, conduits connecting each of said pumps with said reservoir of driving fluid, a system of conduits connecting the driving fluid compartment of each of said pump chambers with said pumps, valve means in said system of conduits for controlling the flow of driving fluid between the reservoir of driving fluid and said chambers and thereby causing displacements of said diaphragms in one direction and then the other, said valve means comprising a valve housing having port means in communication with said conduit means, piston means slidable within said valve housing from one end to the other, opening and closing said port means, said conduit means to both of said pump chambers being opened when said piston means is in an intermediate position of travel withinsaid housing, rod means aixed to said diaphragms and movablev therewith Vso as to cause a simultaneous discharge of driving uid into the respective compartments of 4said pump chambers over a portion of the discharge stroke of said diaphragms, conduit means connecting the drilling fluid compartments of said pump chambers with the drilling Huid reservoir and a Well borehole, and a plurality of valves in said drilling uid conduit means for alternately connecting said pump chambers to said reservoir of drilling uid and then said well borehole.

5. The apparatus of claim 4 wherein the valve means for controlling the flow of driving uid between the reservoir of driving luid and the pump chambers formed in said apparatus is a flow reversing device, said device comprising a casing in Huid communication with said system of conduits, piston means slidably mounted in said casing for alternately directing the driving iluid to rst one pump chamber and 'then the other, and servomotor means connected to said piston means for actuating said piston means.

6. The apparatus of claim 4 wherein the valve means for controlling the flow of driving fluid between the reservoir of driving fluid and the pump chambers formed in said 'apparatus is a ow reversing device, said device comprising a casing, piston means slidably mounted in said casing for alternately directing the driving uid to first one pump chamber and then the other, servomotor means connected to said piston means for actuating said piston means, conduit means in communication between the force pump and said servomotor means, and valve means in said conduit means adapted to be alternately actuated by the rod means afxed to the diaphragms.

7. The apparatus of claim 4 wherein the valve means for lcontrolling vthe flow of driving fluid between the reservoir of driving fluid and the pump chambers formed in said apparatus is a ow reversing device, said device comprising ay casing, piston means slidably mounted in said casing for alternately directing the driving uid to irst one pump chamber and then the other, a servomotor piston connected to said piston means for actuating said piston means, iluid pressure conduits in cornmunication between the force pump and either side of said servomotor piston, a slide valve mounted in each of said lluid pressure conduits, said valve having an axial bore therethrough, rod means slidably mounted in said axial bore and connected to one 'of said diaphragms, stop means affixed near each end of rod means, said stop means being adapted to contact the valve surrounding the rod means for alternately opening and closing said valve on iiexure of the diaphragm in opposite directions.

References Cited in the le of this patent UNITED STATES APATENTS 2,186,972 Hollander Jan. 15, 1940 2,212,667 Mayer Aug. 27, 1940 2,260,306 Ferguson Oct. 28, 1941 FOREIGN PATENTS 744,815 France Apr. 27, 1933

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