US2351322A

US2351322A - Bottom hole regulator

Info

Publication number: US2351322A
Application number: US426634A
Authority: US
Inventors: Crake Wilfred St Maur Elmore
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1942-01-13
Filing date: 1942-01-13
Publication date: 1944-06-13
Anticipated expiration: 1961-06-13

Description

June 13, 1944- w. sT. MAUR ELMoRE cRAKE l 2,351,322

BOTTOM HOLE REGULATOR bq Has Affomzg:

June 13, 1944- .w. sT. MAUR ELMoRE cRAKE A 2,351,322

BOTTOM HOLE REGJLATOR Filed Jan. 13, 1942 2 Sheets-Sheet 2 Q .7 a \'9a Inven'ror: Wlh'rzd. ST. Manuf* Elmore Cmkz -Patented June 13, 1944 BOTTOM HOLE REGULATOR Wilfred St. Maur Elmore Crake, Houston, Tex., assignor to Shell Development Company. San Francisco, Calif., a corporation of Delaware Application January 13, 1942, sei-a1 No. 426,634

(cl. 16e-2) l5 Claims'.

The present invention relates to methods for controlling the dow of oil and gas wells, and pertains more particularly to well flow regulating means adapted to be located in thebottom of the well.

To preserve the formation gas pressure which, in flowing wells, forces the oil to the surface through an eduction tube, valves, or chokes'have been installed in the bottom of the well. These chokes or .bottom hole regulators cause the gas dissolved in the oil to be expanded and liberated at the bottom of the well, and thus permit the lifting of the oil to the well surface at lower gas-oil ratios. the gas in solution in the oil during its flow through the formation, whereby the viscosity and surface tension of the oil are reduced and the resistance to the flow of the oil through the formation is decreased.

It is highly desirable to flow a well at a constant rate and to maintain a steady pressure at the inlet and outlet ends of the eduction tube, since it is under these conditions that most emcient and economical well production is obtained.

The use of most bottom hole regulators is however subject to' dimculties of installation, adjustment and removal. Some bottom hole regulators, such as the fixed orice type, being dependent upon constant pressures on either side of the orice for constant ilow, usually require a second control point at the surface to exert sumcient bach pressure for controlling the volume to a desired amount, since it is costly and impractical to remove bottom hole chokes for frequent adjustment. The back pressure at the surface has a marked effect on flow emciency or heading, since a comparatively small surface back pressure increase reduces the volume of the rising fluid, slows its travel, and accentuates surging or heading in the tubing, thus largely or completely nullifying.

the benecial eects of the bottom hole choke. y In other regulators, a constant pressure drop is maintained at the inlet or bottom end of the eduction tube by means of a spring-loaded `choke or valve, while secondary control is obtained at or near the surface with an additional orice or choice. These regulators, since no compensation isobtainable for variations in bottom hole pressure without removing and readjusting the bottcm hole choke, likewise fail to fulfill the requisite conditions for most eilcient operation.

lt is therefore an object of the present invention to provide an improved oil well bottom hole regulator for obtaining an efficient flow or. production of oil from oil wells.

it is another object of this invention to provide Further, these regulators hold` i an improved bottom hole regulator for oil wells, which is remotely controlled from the surface of the well.

It is a further object to provide an improved bottom hole regulator for oil wells, which is substantially independent of variations in bottom hole pressure.

It is likewise an object of this invention to pro- ,vide means including an improved bottom hole regulator for extending the owing life of oil wells.

Other objects will be apparent from the following description, taken in reference to the drawings, wherein:

Figure I is a longitudinal cross-sectional view of the upper portion of an embodiment of the bot.

tom hole regulator of the present invention.

vFigure 1I is a longitudinal cross-sectional view of the lower portion of an embodiment shown in Figure I.

Figure Ill is a longitudinal cross-sectional view of a modification of the upper portion of the embodiment shown in Figure I.

Figure IV is a diagrammatic view of a well showing the surface control equipment and the present bottom hole regulator installed in the tubing of a. well.

Figure V is another diagrammatic view of a well showing the present regulator installed within the casing of a well.

Briefly, the bottom hole regulator of the present invention comprises conduit means, such as a tubing string, extending down into the well together with an orice associated with the lower portion thereof through which the well fluid must flow, valve means for regulating the fluid ilow through said orifice, resilient means for urging said valve means into 'open position, hydraulic means extending to the well surface for adjusting the position of said valve from the surface, and means for neutralizing and eliminating the effect of bottom hole pressure variations on the position of the valve, whereby the downward force of the hydraulic means which `tends to close the valve is balanced against the upward force of the resilient means together with that of the pressure on the outlet or downstream side of the valve, which tends to open said valve.

Figure lV of the drawings diagrammatically illustrates the position ofthe bottom hole regu-v lator of the present invention in a casing i of a Well. The casing i Yextends from a point Iabove the ground level down to the bottom of the well, the top of the casing i being closed by a casing head 2. A tubing string 3 extends down through the casing i and terminates in. a perforated plug lower portion of the tubing string 3 and thence up through the tubular extension 8 and the regulator 8 and from there maybe conducted to the surface through a flow string or eduction tube 9 rising from the top of the regulator 8.

Referring to Figures I and II of the drawings,

a preferred embodiment of the present bottom hole regulator comprises a tubular shell I5 enclosing a chamber' I5 which communicates with the tubular extension 8 by means of ports I1.

Connected to the upper end of the tubular shell4 I5 is a tubular member I8 which forms an ex-` `tension |8a of the chamber I6 and carries in its lower portion a perforated valve stem guide |9 and in its upper portion a valve orifice and seat ring having a port 2l and .-seat 22. A coupling y connects the upper portion of the tubular member I8 with the lower portion of a plug member 26 and forms therebetween a valve chamber 21. Fluid passes through the regulator 8 through the lower ports |1 into the chamber I8, and through perforated stern guide I9 to chamber |6a, through the valve port 2| into the Vvalve chamber 21, and thence through passages 28 in the plug member 28 to the flow string 9.

A reciprocablerod or stem 3| extends coaxially through the valve orice 2| and carries a valve 32 which is adapted to close the valve orifice 2| by contacting the valve seat 22 upon downward movement of saidreciprocable stem 3|. The rod 3| extends downward from the valve 32 through Fluid now passes from the oil sand K through the perforated plug 8 up through the M and-rod 3| by the spring 43 is regulated by hollow adjusting nut 35, after which the adjusting nut 35 is locked in the desired position by iocknut 41.

The upper end of therod 3| is highly polished and forms a piston 3|b which fits slidingly into a sleeve cylinder 5| extending into the'chamber 52 ofthe plug member 25. The position of the piston 3|b and therefore of the valve 32 is regu-V lated by adjusting the pressure within the chamber 52, which communicates with the surface.

This communication may be obtained through channel 55 extending from the chamber 52 upwardly to the annular space 55 between the flow string or eduction tubing 9 and the outer tubing 3. A perforated plug 51 is preferably attached to the end -of the channel 55 in the plug member 28 to prevent debris from falling into and plugging channel 55. Likewise, a tubular element 58 forming an upwardlyA opening cup, is attached to the upper end of the plug, member' 28, inorder to prevent sediment from lodging between the regulator Band the outer tubing 3 and preventing the removal of the regulator.

' flow string 9 extends from the regulator 6 through the perforated guide I9, a hollow adjusting. nut

35, 2and into a sleeve 35 fittedV into chamber 31 formed in 'the lower end of the tubular shell I5. The lower end 3| a of the rod 3|, which flts into the cylinder 38, is preferably formed with a crosssectional area substantially equal to that of the valve port 2|, and a pressure-equalizing passage 38 extends from the chamber 31 below the lower end of the rod 3| to the chamber 21 about'the valve orifice 2|. In this manner, the bottom hole pressure in chambers I6 and |8a below the valve 32 acts upwards on the .valve 32 with a force substantially equal and opposite to that exerted by said pressure downwardly on the lower piston end 3|a of the rod 3| and has therefore little effect on the movement of the rod 3|. Also, the pressure in chamber 31 being the same as in chamber 21 due to passage 38, the pressure upward on the lower end 3|a of the rod 3| acts against the pressure downward on the valve 32 and has likewise no eifect on the valve movement except insofar as the cross-sectional area of the rod 3| above the valve 32 somewhat reduces the effects or downward force on the valve 32.

The adjusting nut 35, which is threaded into a cage 4| attached to the tubular member I 8, carries on its upper end a recessed member I2, into which ts the lower end of a spiral spring 43. The upper end of the spring I3 ts into an upper recessed member 44. which is threadably attached to the rod 3| and locked in position thereon after assembly by nut 85 and locknut-. The amount of upward thrust on-the upper recessed member the ytop of the casing head 2 and is thereabove fitted with a back-pressure valve 80, which keeps a constant pressure on the top of the flow string 9. The annular space 56 between the ow string 9 and the outer tubing 3 is filled with a control fluid yand is connected at the surface by means of a pipe 8| to a control fluid reservoir tank 82. Preferably, the. control means comprises a control fluid consisting of liquid, such as oil, water or the like, filling the control chamber 52, chani nel 55, annular space 58, and the lower portion of the tank 82 and gas filling they space above the liquid in the tank 82. 'I'he liquid is kept at apy Yproximately constant level, for which purpose a sight glass or gauge 83 is provided on the tank 82. Gas is pumped into the tank under pressure by means of a valved pipe 84 to exert the controlling force on the regulator piston 3|b, the combined liquid and gas pressure being required to balance the force of the spring I3 below the regulator valve 32.

'I'he mode of operation of the regulator may be best described algebraically; therefore, let

A1=Area of control cylinder 5| in square inches', An=Area of valve orifice 2| in square inches.

A3=Area of valve rod 3| below valve 32 in square inches. A4=Area of valve rod at 3|a. P1=Gas pressure in control tank 82 at surface,

lbs. persq.'in.

`l='2=Hydrostatic liquid pressure in control cham- With the valve 32 partially open, the forces acting on the valve are as follows:

(a) Downwards (Pi-I-Pz) A14-P: (Az-Aa) (b) Upwards l P4`(A2-A3) -I-PJAH-Ps For balance (Awami-trataran duce-.43) waa-Pr Asl shown in Figure IV, the eduction tube or Since P1, Ai, Ps, are xed and Az-As is small but larger than A4, a reduction of pressure P3 in chamber 2l will cause the valve to open or an increase in pressure will cause the valve to static pressure Pz, and the volume of the tank 82 is made large so that leakage of fluid or adsorption o gas does not cause appreciable differences in control pressures and, therefore, of ilow. Also, expansion of the fluid in the control column or surface temperature changes should then not cause appreciable recompres'sion in gas pressure Pi after well fiuid flow has settled down to steady conditions. Changes in the operating range of the regulator can be made by simple changes in the size of p arts 3io, 3Ib, 36, 63, and 5l as required to suit conditions.

It will be readily apparent from the above description that various modiilcations may be made without departing from the spirit of the present invention as deflnecl by the appended claims. For example, as shown in Figure III, passages 28a provide fluid communication between the valve chamber 2 and the annular space 56 between the outer tubing 3 and a small control tubing string 9a, whereby Well iluids iiow upwards through the regulator t and the annular space 't instead of a central eduction tube 9, as in Figure I. The lower end of the control string 9a is preferably fitted with an annular sealing ring dt and thereby engages tightly Within the coaxial counterbore Si which communicates with the control chamber 52 through a debris-catching screen t8. Likewise, if desired, as shown in Figure V, the regulator t may be fitted directly within the casing string i whereby the outer tubing 3 and the tubing packer l may be omitted and, the casing packer 5 and perforated plug tl or screen carried by the regulator tubular extension 3.

ln wells which have declined to the point where they will no longer flow naturally, the bottom hole regulator of the present invention is particularly eiective and advantageous when used in conjunction with a ow string having a small diameter bore, as illustrated in Figures I and Il, so as to permit passage of iiuid to the surface at suitable velocities and to prevent or greatly minimize heading" or surging The use of a flow tubing with the proper small diameter bore, depending on the range of flow rates, will permit the raising of a given volume of fluid to the surface at the minimum expense of bottom hole energy. Intermittent ow absorbs considerably more energy per unit of fluid delivered at thesurface than steady ow, which is the most desirable method of producing oil wells'.

With this arrangement of a small bore ow per cent. By using a small bore flow string, which is preferably suitably insulated, such as with a lining of cement or thelike, heat loss by heat exchange will be minimizedand the velocity of ow will be sumciently high to insure that the temperature of the crude oil produced will be above the temperature at'which any paraillnv present accumulates.

For example, many wells with present size of tubing and production methods, will not ilow naturally after having been shut in if the bottom hole pressure drops below 800 lbs. per sq. in. However, the wells will continue owing through small sized tubing with as low as 400 lbs. per sq. in. bottom hole pressure. The steady ow characteristics resulting through the use of small diameter insulated tubing would have the additional advantage of decreasing the rate of water encroachment in contrast to the presently used stop-cooking or high rate intermittent ilow, which is necessary to reduce parafiin accumulation in the tubing, but which hastens production of water vfrom the well and increases the rate of water production after it rst appears. The present combination thus postpones and sometimes eliminates the need and expense of salt Water disposal facilities.

For this purpose, tubing strings having diameters of 1% to 1A; inches may be used, depending on theY flow rate. For example, under certain duid conditions a Asuitably insulated, e. g. cement-lined, flow tubing having a one-half inch borewill produce oil continuously at the rate of one barrel an hour, while maintaining the tubing inlet pressure at 500 lbs. per sq. in. by means of the present bottom hole regulatorand the surface exit pressure at 30 lbs. per sq. in. by means of a back pressure valve, whereby there is obtained eicient continuous flow over a long period of time. In such small tubing strings and at such small iow rates, it is essential that the inlet pressure to the tubing string be maintained very closely to a' predetermined pressure, which condition or emcient new can be obtained by the use of the present bottom hole regulator.

I claim as my invention:

1. 1n. a bottom'hole regulator for oil wells having an eduction tubing and casing string depending thereinto, said regulator being adapted to be positioned in the lower portion or the well, passage means longitudinally through said regulator, said passage means comprising a valve ,port a reciprocable stem carried within said for urging said valve into open position, hy-. draulic means for urging said valve into closed Y position, said hydraulic means comprising an upstring, together with the present bottom hole regulator`which is largely independent of variations in bottom hole pressures, the natural flowing life oi a Well can be considerably increased,

, for example, under certain conditions for an adper cylinder adapted to receive slidably the upper parting fluid pressure to said valve stem in said cylinder through said passageway, a lower cylinder adapted to receive slidably the lower thickened portion of said stem, and equalizing passage means to provide pressure communication between the lower cylinder and the housing space directly above the valve, whereby the position of the valve is regulated from the surface and is substantially unaffected by varying pressures below the regulator.

2. In a pressure regulator adapted to be positioned in the bottom portion of a well, means forming a flow passage through said regulator for the well fluid to the surface, a valve seat in said ilow passage means, a pressure-responsive valve element adapted to cooperate with said valve seat for controlling the ilow of fluid through said regulator, a reciprocable stem carrying said valvel element, resilient means for urging said valve element into open position, hydraulie means acting upon said stem and extending from the upperend of said stem to the well surface for maintaining a substantially constant vpressure on said valve `element counter to the pressure of said resilient means, and equalizing Passage means extending from the lower end of the valve stemto the space on the outlet side of the valve, whereby the ei!ects of fluctuations in pressure below the pressure regulator on the operation of the valve vare substantially eliminated.4

3. In a pressure regulator for oil wells, a passage for the ilow of well fluid to the surface, a valve seat insaid flow passage, a reciprocable valve element adapted to cooperate with said valve seat for controlling the iiow of uid through said ilow passage, a reciprocable stem' rigidly carrying said valve element, resilient means adapted to urge said valve element into open position, hydraulic means extending to the surface for applying a tluid control pressure to one end of said stem in opposition to the eiiect of said resilient means on said valve, and equalizing passage means extending from the other end oi' said valve stem to said now passage on the outlet side oi' the valve for applying to the other end oi'said valve stem the pressure at said outlet side oi' the valve.

4. In a pressure regulator for oil wells, a passage for the flow of well fluid to the surface, a valve seat in said flow passage, a valve element opening to one of said cylinders for applying to a first piston formed by the rst end o1 said stem, a fluid control pressure in opposition to the eiIect of said resilient means on said valve, and equalizing passage means in communication -between the other cylinder and said flow passage on the outlet side of the valve for applying to said second piston formed by the second end of said stem the pressure on said outlet side ofthe valve.

5. A well pressure system for naturally flowing wells comprising the combination of an eduction string and a control fluid string concentricaily extending into the well from the surface, a

packer within the lower portion of the well sealing the annular space between said strings, a bottom hole regulator forming a passage through said packer, a valve seat in said passage, a valve element adapted to cooperate with said valve seat for controlling the iiuid ow through said passage, resilient means ior urging said valve element into open position, ilrst piston means attached to said valve, said means being responsive to pressure in the control fluid string for urging said valve into closed position, second piston means attached to said valve, said second piston means being responsive to rising pressure in said flow passage on the inlet side of the valve for closing said valve and to rising pressure in said iiow passage on the outlet side or the valve for opening said valve, and control means at the surface for regulatingthe pressure in said strings. WILFRED ST. MAUR ELMORE CRAKE.