METHOD AND MEANS TO PUMP A WELL

Abstract: Method and means to pump a well with a hydraulically-driven downhole pump (15) as powered by a hydraulic surface unit (1), including a downhole filter assembly (71) and a flowline mounted oil leach (27) for supplying makeup oil to the surface unit.

Description: Method and Means to Pump a Well Technical Field This invention relates generally to methods and means for pumping oil and water from deep wells and more particularly to the use of hydraulically-driven pumps. Although fluid power has long been used to drive such pumps, severe difficulties still exist in the pumps now available such as sand cutting, sand fouling, ~ ~ excessive use of energy, excessive downtime and excessive maintenance. Although the use of sucker rods to operate a downhole reciprocating pump is the oldest and most widespread methods, the well known high first cost and endless maintenance problems inherent in sucker rod systems have almost become accepted by many operators as inevitable which, unfortunately, drives up the 10 cost of oil and gas and many "crooked holes" cannot be pumped at all with the use of sucker rods. The practice of "gaslifting" liquids from wells by injecting pressurized gas into a column of liquid within a tubing is well known to be an inefficient system when compressors are required to compress the gas before injection, and it cannot be used at all in most deep wells of today. 15 Downhole hydraulic pumps have been used since 1935, but are used in less than 1% of pumping wells today because of excessive cost and excessive maintenance. Typical recommendation is to change the pump every two months. Therefore, particularly with regard to such wells as offshore wells which are generally both deep and directionally drilled, when the pressure of their 20 producing formation declines such that they will not longer flow on their own, a more reliable and efficient method and means for pumping is needed by the industry to gain many millions of barrels of oil and billions of cubic feet of gas, as the present invention provides. In many oilwells, paraffin that may be present in the formation oil may 25 precipitate from the oil as it nears the surface and deposit on the walls of the conduit and thereby reduce the flow area to make remedial action necessary which may result in considerable expense and lost production. Background Art 30 U.S. Patents 2,362,777 and 3,123,007 disclose early systems for hydraulically driving a reciprocating well pump but neither have bearing on the present invention. Many similar patents exist, some having fluid motors for attachment to conventional pumps or to operate a string of sucker rods which in turn operate a conventional downhole pump. Coberly patent 2,952,212, the type pump that virtually all downhole hydraulicallydriven pumps in use today comprise, operates by co-mingling spent power fluid with produced liquid from the well which requires separation and purification of all of the power fluid before recirculation to the downhole pump. A later Coberly patent, 3,005,414, employs a power fluid string and a separate conduit to return exhaust power fluid to the surface and a production string to convey produced liquid to the wellhead as does the present invention. However, frequent clogging of small flow paths in that type of pump by solids entrained in the power fluid, require frequent replacement of the pump. As with all hydraulic equipment, some leakage may occur at moving seals, at pipe fittings or the like such that makeup fluid is required to replace such leakage so as to allow for continuous operation of the system. The open system described by Coberly causes co-mingling of the exhaust power fluid with the produced well fluid which in many wells may be mostly water, thereby requiring a production separator to process the entire stream of produced fluid mixed with exhausted power fluid so as to make available power -fluid for continued operation. A closed system does not mingle produced fluid with exhausted power fluid and therefore, it is not required to separate the two for each cycle of the fluid, however, makeup fluid is required by the system to offset aforementioned leakage. Makeup fluid for a closed hydraulic system is usually provided by the operator keeping track of oil level in the tank and periodically delivering oil to inject into the system. Unattended operations in the field can thereby be jeopardized by any delay of that service. It is therefore desirable to prevent the need for and cost of separating all power fluid for each cycle and to have makeup pow-er fluid automatically supplied to the system without the need for extended supply lines from distant tanks and/or treatment facilities, or the manual replenishment of oil to the system. Presley patent 4,233,154 discloses a production separator, normally mounted a considerable distance from the wellhead and in some cases miles from the wellhead, that makes provision to pump fluid back to the well for driving a downhole pump in an open system as taught by Coberly 2,952,212. No prior art known to the inventor provides for a downhole filter so as to exclude particles, within the power conduit being used to convey pressurized fluid downwardly to the pump motor, from entering the pump motor; automatically provides at the wellhead, for the proper volume of makeup fluid to offset leakage from a closed system; prevents precipitation of paraffin from the well fluid by heating power fluid used to drive a downhole pump; eliminates the hydrostatic pressure differential across the wall of the conduit used to convey pressurized power fluid. Such omissions may partially explain the extremely limited application Disclosure of Invention The present invention provides for method and means to sufficiently clean hydraulic fluid in a closed system used to drive a downhole well pump and to automatically make up, at or near the wellhead, for power fluid lost from the system. One or more filter elements are positioned in a joint of tubing mounted immediately above the downhole pump so as to exclude from the pump, solid particles that may be in the supply or return tubing conveying power fluid to or from the pump. As depicted, the filter elements comprise conically formed filter screens, supported at a lower section near the apex of the cone against downward movement by an axially disposed tension member attached at an upper end above the screen with the tubing wall within which the screens are mounted. An upper section of the screen, being of maximum diameter, is mounted with an inner surface of the tubing so as to direct all fluid flow through the screen. A device much smaller than a production separator is mounted with the flow line near the wellhead so as to receive a small portion of the fluid produced from the well, separate an amount of oil therefrom sufficient to offset leakage from the closed system, such that the system may continue to operate unattended and without the necessity to periodically furnish oil to the system by other means. Tubing connections are provided so as to improve in combination, improved clearance, axial strength and sealability, arranged in a concentric pattern with a conduit for conveying pressurized power fluid at the center within a conduit for conveying exhaust fluid back to the wellhead, such that the hydrostatic pressure across the wall of the centermost conduit is balanced. The pressurized power oil being pumped downwardly to drive the bottom hole pump may be heated at the surface so as to prevent precipitation of paraffin from the well fluid and thereby prevent reduction of the flow area of the conduct conveying well fluid to the wellhead. Brief Description of the Drawings Figure 1 depicts a general arrangement of means that may be used to practice this present invention. Figure 2 depicts a small separator or "leach" for separating a minor portion of oil from a flow line. Figure 3 is a vertical section of a filter screen in accord with the present invention. Figure 4 depicts a preferred position for the downhole filter of the present invention. Detailed Description of the Invention Figure 1 depicts a surface-mounted source of hydraulic power henceforth called the surface unit, shown generally at 1 comprising: tank 2, motor 3, pump -4- 4 and float valve 5, motor 3 being of whatever type most convenient for each well location. The wellhead shown generally at 6 may comprise: casing head 7 mounted with casing string 8 and in communication therewith; tubing head 9 mounted with production tubing string 10 and in communication therewith; tubing head 11 mounted with return tubing string 12 and in communication therewith; tubing head 13 mounted with power tubing string 14 and in communication therewith. Bottom hole pump 15 which may comprise features as disclosed in my co-pending U.S. applications SN 421,503 filed 22 September 1982, SN 532,845 filed 16 Septemer 1983, and an application entitled "Hydraulically Driven Downhole Pump" filed herewith. Pump 15 may be installed with return string 12, positioned on the lower end thereof and sealed as at 16 with the lower portion of production string 10 through which it is inserted, in any suitable manner. Filter joint 17 may be mounted with and immediately above pump 15 so as to filter all power fluid flowing to the pump immediately before the power fluid enters the pump so as to exclude all solid particles entrained with power fluid that may otherwise damage or clog the pump. A lower member 18 of remotely actuated tubing connector 19, which may comprise features disclosed in my co-pending U.S. application SN 421,503, may be connected with the upper portion of filter joint 17 so as to allow connection with upper member 20 of connection 19 mounted with the lower portion of power string 14 after power string 14 is inserted into and lowered through return string 12 to mate memers 18 & 20. Pressured power fluid may then be conveyed from pump 4 through conduit 21, through head 13, downwardly through power string 14, through connection 19, through filter joint 17 and thence to drive pump 15. Exhaust power fluid from pump 15 may return upwardly through annulus 22 formed between strings 12 and 14 through head 11 and conduit 23 for return to tank 2. Well fluid within which pump 15 may be immersed as at 24, may be produced upwardly through annulus 25 formed between strings 10 and 12, through head 9 and thence through flowline 26 to surface treatment facilities and thence to storage tanks or pipeline. Connectors for some or all of the tubing strings 10, 12 & 14 may be formed as depicted and described by my co-pending PCT application filed herewith and entitled "Oilw ell Tubing Connector" so as to provide conduits within the space available in typical oilw ells and to provide tubing joints having adequate axial strength and sealing capability. So as to provide makeup power fluid that may have leaked from the system, leach 27 to be later described, may be connected with an upper opening in the flowline 26 as with tee 50, so as to supply makeup fluid via conduit 28 to conventional float valve 5 such that float valve 5 will admit makeup fluid from Now referring to Figure 2, leach 27 may comprise: tubular shell 29 sealingly affixed with an upwardly positioned outlet of tee 50 and enclosed at an upper extremity as at 30; flow restrictor 31 mounted in flow path 32 of flowline 26 so as to create a differential fluid pressure across flow restrictor 31 sufficient for purposes later described, while allowing the vast majority of the volume of flow within the flowline to pass under the restrictor together with solids that may be entrained so as to maintain the leach as self-cleaning; gas conduit 33 extending from an upper portion of shell 29 to a position within flowpath 32 downstream of restrictor 31 may be of sufficient capacity so as to vent gas that may collect in the upper portion of shell 29, the differential created across restrictor 31 being sufficient to exceed the hydrostatic pressure then existing between the inlet and outlet of conduit 33; radially positioned wall 34 formed in a lower portion of shell 29 and around conduit 33 so as to divide shell 29 into upper chamber 35 and lower chamber 36, wall 34 being formed with openings as at 37 formed therethrough for cooperation with upper surface 38 of water shutoff valve 39 mounted therebelow so as to seal openings 37 to prevent the flow of water therethrough; chamber 40 formed within upper portion of conduit 33 in communication therewith having downwardly facing wall 41 formed with openings as at 42 therethrough for cooperation with an upper surface 43 of oil shutoff valve 44 so as to prevent oil from entering conduit 33; oil chamber 45 formed within shell 29 intermediate valve 44 and wall 37 having an upper wall 46 formed with openings as at 47 therethrough for cooperation with a lower surface 48 of gas shutoff valve 49 mounted above wall 46 so as to seal openings 47 and thereby prevent the flow of gas therethrough; conduit 28 connected so as to convey oil from chamber 45 to float valve 5 of Figure 1; membrane 51 attached with an upper portion of restrictor 31 and extending upwardly to wall 52 extending from the downstream side of the lower chamber so as to form water chamber 53 open at a lower extremity to flowpath 32 downstream of restrictor 31. Water shutoff valve 39 may be formed of suitable material and dimensioned so as to float in water and to sink in oil such that should water rise within shell 29 to approach wall 34, valve 39 will rise and seal openings 37 so as to prevent the flow of water therethrough and when water is at a lower level, oil and gas may rise through openings 37 to enter upper chamber 35. Oil shutoff valve 44 may be formed of suitable material and dimensioned so as to float in oil and to sink in gas such that should oil rise within shell 29 to approach wall 41, valve 44 will rise and seal openings 42 so as to prevent the flow of oil therethrough and when oil is at a lower level, gas may pass through openings 42 into conduit 33 and thence re-enter flowpath 32 as at 54. Gas shutoff valve 49 may be formed of suitable materials and dimension - so as to float in oil and to sink in gas such that should the oil level falls with. . shell 29 to approach wall 46, valve 49 will descend and seal openings 47 so as to prevent the flow of gas therethrough and when oil is at a higher level, oil may pass through openings 47 into oil chamber 45 and thence through conduit 28 and to tank 2 as regulated by float valve 5. Should it be desirable in some applications, restriction 31 may be adjusta -- as by providing gate valve stem 55 mounted within hub 56 formed with tee by means of screw threads 57 and sealed as by packing 58 around stem 55 so as to allow rotation and axial movement of stem 55 without leakage from flowpath 32. Restrictor 31 may be formed with a conventional tee slot to fit radial flang- 74 formed on the end of stem 55 so as to allow stem 55 to push and pull cπ restrictor 31 which may be slidably mounted as the gate of a conventional ga;s valve. So as to prevent unwanted flow above restrictor 31, plate 59 may be affixed so as to overlap membrane 51 and restrictor 31 over the full range of adjustment of the restrictor. Now referring to Figure 3, a filter assembly shown generally at 71 may compri a suitable filter material formed as the frustrum of a cone as at 60 mountec within tubular filter joint 61 and supported by any suitable attachment as at 62 with tension member 63. Tension member 63 may be attached with an uppe r portion of filter joint 61 in any suitable manner as by a bar 69 of Figure 4 positione 1 across the inner diameter of filter joint 61 and having threaded ends for matin-,- with a portion of internal threads formed in the upper portion of the filter joint. The upper and larger end of cone 60 may be mounted with member 64 formed of elastomer or the like so as to prevent fluid flow around the upper peripher;; 65 of cone 60 so as to direct all flow through filter joint 61 to be filtered through cone 60. Figure 4 depicts a series of cones 65, 66,67, & 68, attached to tension member 63 and mounted within filter joint 61 as previously described for the purpose of extending the usable life of the filter assembly. For example, if it was desir≤ . to prevent particles larger then ten microns from entering pump 15 and seal within strings 12 and 14 constituted particles ranging from 10 to 500 microns, a single fine filter would become prematurely clogged with large particles whereas a single course filter would pass particles that would damage pump 15. Therefore, it may be desirable to make: cone 65 to filter 400 micron particles; cone S6 to filter 200 micron particles; cone 67 to filter 100 micron particles, and cone 68 to filter 50 micron particles. A lower end of tension member 63 may be fastened at 70 as described at 69 to secure the assembly during handling aπc: shipment. So as to be able to run economically feasible sizes of tubing for powe -?- string 14 and return string 12 and still provide for flow paths having adequate cross sections so as to allow passage of power fluid within practical limits of pressure drop, flush joint tubing joints as disclosed in my co-pending application entitled "Oil Well Tubular Connection" filed herewith, may be used therefor. Should the well fluid flowing upwardly toward the wellhead be of low enough temperatures to cause precipitation of paraffin that may be a part of the well fluid, oil heater 90 may be connected so as to heat power oil flowing to the well so as to transfer sufficient heat through the tubing walls as required to prevent said precipitation. Operation of the invention may now be understood. After installation of casing string 8, head 7, production tubing string 10 and head 9 in a conventional manner, pump 15, filter joint 17 and lower member 18 of remotely actuated connector 19 may be sealably connected together in the order shown by Figure l. Pump 15 may then be sealably connected to the lower end of return string 12 for insertion donwardly into string 10 so as to connect and lower all joints of string 12. Pump 15 may then be sealably connected with the lower portion of string 10 as disclosed in my co-pending application identified above or by any suitable means. String 12 may then be mounted with head 11 in a conventional manner. Any solid particles such as sand, pipe scale, or such that may fall down within string 14 during or after installation of string 14 will fall into the annulus between string 14 and filter joint 17 or be stopped by filter screens 65-68 so as to preclude such particles from pump 15 during installation. Upper member 20 may now be sealably mounted with the lower end of power tubing string 14 which may then be inserted into and run downwardly into string 12 so as to connect member 20 with member 18 and thereby effect a conduit for delivery of high pressure power fluid to pump 15. String 14 may then be mounted with head 13 in a conventional manner so as to complete the downhole circulation system. An outlet of head 7 may be connected with a gas line so as to receive gas from the formation upwardly through the annulus between strings 8 and 10 and an outlet of head 9 may be connected with flowline 26 so as to receive fluid being pumped by pump 15 upwardly through annulus 25. Conduits 21, 23 and 28 may then be connected with surface unit 1 positioned as desired from the wellhead perhaps 20 feet and as depicted and previously described. A clean power fluid such as filtered crude oil may then be supplied to tank 2 in sufficient quantity to fill tank 2, conduits 21 & 23, tubing strings 12 and 14, being pumped around by surface pump 4 driven by motor 3. Continued pumping by pump 4 will begin operation of pump 15 which will pump well fluid upwardly through annulus 25 and thence through flowline 26 to heaters, treaters, separators and storage tanks or pipelines, all at considerable distance from the wellhead, from hundreds of feet and often miles. -8- A conventional filter may be provided with surface unit 1 to remove particles larger than 10 microns from the power fluid before the fluid enters pump 4, however, as pressurized power fluid flows through conduit 21 and power tubing string 14, scale, sand and such may precipitate from within conduit 21 and string 14 that could cause damage to pump 15. Therefore, as the power fluid flows downwardly through filter joint 17, cones 65, 66, 67, and 68, successively filter smaller particles from the flowstream to thereby protect pump 15 from damage by the particles in a manner to effect extended service life of the filter assembly. Particles precipitating into the power fluid flowstream from within string 14, if finer than can be filtered by cone 68, will pass through pump 15 only one time, to be filtered at surface with 1 whose conventional filters may be changed as required without removing string 14 from the well. The filter materials of cone 68 were selected to retain particles larger than 50 microns, such particles once through should cause no appreciable wear to pump 15 and the useful life of the downhole filter system should be adequate. As the well fluid enters tee 50 as at arrow 72, a minute upper portion of the lighter fluids will tend to stagnate upstream of restrictor 31 and rise into lower chamber 36 as at 73, while the vast majority of the fluid and all sediments will flow under restrictor 31 to continue along flowline 26 and thereby create a fluid pressure differential across restrictor 31, sufficiently greater than the pressure differential existing between the uppermost portion of chamber 35 and the lowermost portion of chamber 36 so as to cause gas to flow downwardly through conduit 33. Should a pressure differential adjustment be provided, stem 55 may be rotated so as to cause an optimum pressure differential" to operate the leach. As a mixture of oil and gas rise in chamber 36, residual water, separating from the mixture, will fall and should membrane 51 be provided, some of the residual water may flow therethrough due to the differential pressure. Should water rise to approach wall 34 as could happen on startup, valve 39 will rise and prevent further upward flow until that water is replaced with accumulated oil, upon which, valve 39 will fall so as to allow oil and gas to rise through openings 37 into chamber 35. Gas passing upwardly within chamber 35 will pass around oil chamber 45 toward the upper portion of chamber 35 and thence through openings42 into conduit 33 so as to re-enter flowstream 32 as at 54. Should oil rise in chamber 35 to approach wall 41, valve 44 will rise and prevent flow of oil into openings 42, however, should accumulated gas within chamber 35 push the oil level back down, valve 44 will fall to once again purge the gas. Should the oil level within chamber 35 drop to approach wall 46, valve 49 will fall and prevent gas from entering conduit 28 via openings 47 and chamber 45, however, as the oil level again rises, valve 49 will rise to allow the flow of oil to tank 2 as regulated by float valve 5 so as to maintain the oil level within tank 5 at a desired level. It is therefore clear that the present invention may provide adequate makeup oil automatically to the surface unit so as to allow continuous unattended operations thereof. OMPI

Claims: t u I claim 1. A method for pumping a well with a hydraulically-driven pump, hydratiiϊc power being provided by a surface unit positioned near the wellhead. comprising: automatically separating from the wellhead flowline, a votorr.a of makeup oil as may be required by the surface unit; supplying the make':? oil to the surface unit as may be required to maintain oil therefore, wi: a desired range of volume. 2. Method for automatically separating oil from a wellhead flowline;, comprising: positioning a flow restrictor within the flowpath of the flowline; providing an enclosed recess of suitable dimension over the flowpath upstream of the restrictor such that a small portion of oil flowing in the flow path may rise into the recess while allowing the remaining fluid and entrained particles to flow through the restrictor; venting gas, that may have separated from the oil, from an upper section of the recer i through a suitable vent conduit to the flowpath downstream of th - ■ restrictor. 3. The method of Claim 2 further comprising means positioned in a lower section of the recess which: will allow passage of oil or gas upwardly; will not allow upward movement of water. 4. The method of Claim 2, further comprising means in an upper sectior. of the recess: which will admit gas to enter the vent conduit; which will not admit oil to enter the vent conduit. 5. The method of Claim 2 further comprising means in a section of the recess intermediate the upper and lower sections: which will admit oil to enter a supply conduit connected with the surface unit; which will not admit gas to enter the supply conduit. 6. The method of Claim 3 further comprising means below, said means to prevent upward movement of water: which will allow a small portϊor. of the water to bypass the restrictor; which will not allow oil to bypass, the restrictor to re-enter the flowline. 7. A method for pumping a well with a hydraulically-driven pump, comprising, positioning a downhole filter system in the flowpath of power fluid being- supplied to the pump, upstream with respect to the pump. 8. The method of Claim 7 further comprising: the filter system being positioned immediately upstream with respect to the pump. 9. The method of Claim 8 wherein the filter system is positioned in the well while attached to the pump so as to exclude unfiltered particles from the pump during installation of the system. 10. The method of claim 9 further comprising: positioning the pump and filter system assembly within the well; lowering into the well a string of power tubing for supplying hydraulic power to the pump; connecting said power tubing with an upper section of the filter assembly by means of a remotely- actuated tubing connector so as to convey only filtered hydraulic power fluid to the pump. 11. The method of Claim 7 wherein said filter system comprises: one or more conically formed filter screens or the like mounted within a tubular member used to convey hydraulic fluid and attached at a lower small end to an axially disposed tension member for supporting said screens against downward movement, the tension member being attached at an upper portion with the tubular member; means at the upper larger end of the conical screen to seal with an interior surface of the tubular member so as to direct all flow of power fluid through the screen. 12. The method of Claim 11 wherein: a lower screen is suited to filter out of the hydraulic fluid finer particles than the screen above it. 13. Means for pumping a well including a hydraulically-driven pump, hydraulic power being provided by a surfact unit, comprising a production tubing string being mounted in a well so as to convey well fluid upwardly to the wellhead; a return tubing string being mounted in the well so as to convey exhaust power fluid from the pump upwardly to the wellhead; a power tubing string being mounted in a well so as to convey pressurized power fluid downwardly from the wellhead to the pump wherein: one or more of the tubing strings comprise joints of tubing threaded internally at each end for cooperation with externally threaded couplings. 14. The invention of claim 13 wherein the tubing joints comprise outer diameters of substantially constant dimension. 15. A method for pumping a well wherein a production tubing string is provided for conveying well fluid to the wellhead and a power tubing string is provided within the production string for conveying pressurized power fluid to drive a downhole pump, comprising: heating the power fluid so as to cause transfer of sufficient heat through the wall of the power string to the well fluid such that paraffin will not precipitate from the well fluid and accumulate on walls of the production tubing string. 16. Means for pumping a well comprising: a return tubing string mounted so as to convey exhaust power fluid to the surface from a hydraulically driven downhole pump; a power tubing string mounted within the return string so as to convey pressurized power fluid to the pump from a hydraulic power source mounted at the surface, such that no differential hydrostatic pressure acts across the wall of the power string.

Inventors: WATTS JOHN DAWSON, WATTS, JOHN, DAWSON
Applicants: WATTS JOHN DAWSON, WATTS, JOHN, DAWSON
Application year: 1984
Main classification: E21B43
IPC codes: E21B43, F04B47