US3218977A

US3218977A - Well pumping apparatus and method

Info

Publication number: US3218977A
Application number: US238391A
Authority: US
Inventors: Robert W Scarth
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-11-19
Filing date: 1962-11-19
Publication date: 1965-11-23
Anticipated expiration: 1982-11-23

Description

NOV. 23, 1965 R, W, SCARTH 3,218,977

WELL PUMPING APPARATUS AND METHOD 'PRODUCING FORMATION INVENTOR R .W. S CA RT H Nov. 23, 1965 2 Sheets-Sheet 2 Filed Nov. 19, 1962 INVENTOR. R .W. SCART H United States Patent O 3,218,977 WELL PUMPING APPARATUS AND METHOD Robert W. Scarth, Midland, Tex. (P.0. Box 831, Borger, Tex.) Filed Nov. 19, 1962, Ser. No. 238,391 Claims. (Cl. 103-41) This invention relates to a process and apparatus for use in the production of fluid through an oil well.

A problem common with any fluid producing well, having limited productive capacity and requiringartificial lift, is that of excessive uid drawdown. Such condition occurs when the producing mechanism is operated at a rate exceeding the capacity of the fluid source to supply fluid. Excessive drawdown or pumping off may contribute t0:

(l) Accelerated equipment failures.`

(2) Poor lifting efficiency.

(3) Exposure of the fluid producing formation resulting in mineral deposition on the walls of the formation. Such mineral deposition may impede fluid entry.

Currently, annulus fluid level is controlled primarily by use of a time switch which automatically starts and stops the prime mover. The amount -of on and off time is pre-selected and bears no relationship to varying equipment or down hole uid conditions.

There is a definite need for equipment or apparatus for controlling the amount of lifting (pumping) time as a function of the annulus bottom hole pressure or fluid pressure at the bottom hole pump. It is also often desirable to know the annulus bottom hole pressure in a pumping oil well.

This invention provides a means and method for determining annulus bottom hole pressure in an oil well provided with pumping equipment and controlling the amount of pumping time as aA function of annulus bottom hole pressure. p

Accordingly, it is an object of the invention to provide a process and apparatus for regulating the pumping of tluid from an oil well in response to the annulus bottom hole pressure and/or the weight of the annulus uids. Another object is to provide a method and apparatus for determining the fluid pressure at a datum level of the bottom hole pump. Even though the pump datum is the preferred level to determine bottom hole pressure, this is not to imply that this method is limited to determination at said level. This will be disclosed upon further investigation of said method. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises means in a well for relief of uid pressure in the tubing above a down hole pump when the differential pressure between the fluid in the tubing and the iluid in the annulus outside of the tubing reaches a predetermined value and cooperating means which terminate pumping of fluid from the well to permit iniiux of fluid in the annulus.

Another aspect of the invention comprises a method of determining bottom hole pressure wherein pumping into the tubing with the production line closed is effected until a down hole relief valve between the tubing and annulus is forced open and the surface tubing pressure observed or recorded at the instant of said opening. From the value obtained together with known values the bottom hole pressure at the valve datum level is determined by substituting said values in the equation:

Equation N0. 1 P=H,+P1-.K in which:

P=Bottom hole pressure in p.s.i. P1=Tubing gauge pressure in p.s.i.

ice

Ht=Hydrostatic head in tubing at pump level in p.s.i. K=Dierential opening pressure of the down hole relief valve in p.s.i.

A more nearly complete understanding of the invention may be had from a consideration of the accompanying drawing of which FIGURE l is an elevation in partial cross section of a well equipped with the apparatus of the invention including a down hole pressure relief valve. FIGURE 2 is a fragmentary elevation in partial section of down hole equipment including a pressure relief valve of another structure. FIGURE 3 is an exploded elevation in section of the lower end of a down hole pump with a relief valve of another structure; FIGURE 4 is an exploded pictorial view of the relief valve of FIGURE 3; FIGURE 5 is a cross sectional elevation of another form of relief valve attachable to the bottom of a pump; and FIGURE 6 is an exploded pictorial view of the valve of FIGURE 5.

Referring to FIGURE 1, a well bore 9 penetrates an oil-bearing stratum 12. Well bore 9 is customarily lined with casing 10 which is perforated by holes 14 to admit fluid into the casing. In certain instances, however, casing 10 may not be installed adjacent oil-bearing stratum 12 in which case formation fluids flow directly into well bore 9 constituting an open hole completion. Tubing 16 within casing 10 extends from adjacent the lower end of the casing through the well head and connects with a production ow line 18. Line 19 is connected to the casinghead and permits the withdrawal of casinghead gas from annulus 42. A surface pressure relief valve 20 and a pressure control switch 22 upstream are positioned in ow line 18. A bottom hole pump 24 is sealed with tubing 16 by seating nipple 26 and is provided with a gas anchor 28 on its bottom end. Perforations 29 in tubing 16 allow fluid to flow between the casing and tubing. Pump 24 may be powered by sucker rod means, hydraulic means, electric means or pneumatic means. In FIGURE l, pump 24 is operated by sucker rod 30 which is connected with and operated by pumping unit 32. Prime mover 34 is operatively connected with unit 32 and may comprise any type of power means including an electric motor, an internal combustion engine, etc.

Pressure switch 22 is operatively connected with prime mover 34 by line 36, control 38, and line 40, This control system may be electrical, electronic, magnetic, pneumatic, hydraulic, or manual. When the pressure in line 18 falls below a predetermined minimum, switch 22 operates through control 38 to shut down prime mover 34. Prime mover 34 may be operatively connected to a switch (not shown) which restarts same after a timed interval;

or it may be manually started by an operator as desired when the bottom hole pressurein annulus 42 is adequate to permit resumption of pumping.

Gauge 44 registers tubing pressure at the well head while gauge 46 registers annulus well head pressure. Down hole pressure relief valve 50 is positioned in conduit 52 communicating between tubing fluid 56 and annulus uid 54. Valve 50 comprises a valve seat 59, a ball or -other closure 55, a strong compression spring 57 and a retainer 58.

FIGURE 2 shows another embodiment of the down hole relief valve and associated structure (corresponding elements being numbered as in FIGURE 1) in which pump 24 in tubing 16 Within casing 10 is operated by sucker rod 30. The pump is anchored by seating nipple 26. Pump barrel 60 is provided with ports 62 below standing valve 63 and above seating nipple 26. Gas anchor 28 is -c-oncentric with the pump barrel but of smaller diameter to form .an annular valve chamber 64 open to the casing fluid through ports 66 and tubing perforations 29. At the upper end of the valve chamber, valve port or ports 70 communicate between the annulus fluid and the tubing fluid (passing through ports 62). An annular valve body 72 is biased against the shoulders of port or ports 70 (which functions as a seat therefor) by valve spring 74. This spring provides a predetermined tension on the valve which is regulated to maintain the desired opening differential pressure.

The embodiment of the relief valve shown in FIGURE 2 is preferred to that shown in FIGURE 1 in that it may be removed with the pump without pulling the tubing. FIGURES 3 and 5 show other embodiments of the down hole relief valve which can be installed and removed from the tubing without pulling tubing 16 from the well.

Referring to FIGURES 3 and 4, conduit 76 connects onto the lower end of pump barrel 60 below standing valve 63 and serves as a housing for valve 78. A subjacent conduit 80 attaches to conduit 76 and provides seating cups or hold down device 82. A gas anchor (not shown) attaches to the lower end of the conduit 80.

Valve 78 comprises a valve body S4 which is provided with a conduit or passageway 86 extending axially and then laterally from the axis of conduit 76 through the wall thereof at port 88. Nipple 90 threads through conduit 76 into valve body 84 to hold conduit 86 in alignment with port 88. An annular protuberance 92 on the lower side of valve body 84 forms a seal with seat 94 in disc 96 to close the valve. The radial design of seat 94 provides a concave surface for tubing fluids passing between protuberance 92 and seat 94 to act upon. This design prevents a throttling action of the down hole relief valve and results in a lower differential closing pressure than differential opening pressure.

Passageways 98 in disc 96 allow fluid to pass from valve passageway 86 through conduit 76 into annulus 42, when disc 96 is forced away from valve body 84 and also allows passing of fluid from annulus 42, tubing perforations 29, and gas anchor 28 into pump 24 when valve 78 is closed. The spider construction of valve body 84 cooperates with disc 96 in permitting such fluid flow. Spring 100 is compressed between disc 96 and compression ring 102 which is threaded into conduit 76 and permits variation -or adjustment of the tension of spring 100.

FIGURES and 6 show a variation in the construction of the valve of FIGURES 3 and 4 (corresponding elements being numbered as in FIGURES 3 and 4) which provides unequal seat areas between the tubing and casing sides of the valve. The valve member 104 is designed so that when valve '78 is closed the pressure applied by fluid in tubing 16 acts on a smaller area than that exposed to annulus fluid 54. Orifice 105 in valve member 104 creates back pressure in passageway 106 thereby causing a lower differential closing pressure than `opening pressure for valve '78. Removal of plug 103 from valve body 84 permits installation of seating piston 104. Upon installation of piston 104 in body 84 plug 103 is screwed into valve body S4.

When valve 78 is closed seating member 104 is biased with protuberance 107 thereby effecting seal between tubing fluid 16 and annulus 42. When the pressure applied from tubing fluids 16, times the net cross sectional area of seat 104 exposed to tubing fluids becomes greater than the combined forces of spring 102 compressed against disc 96 and thence seating member 104, plus the annulus bottom hole pressure times the net cross-sectional area of seating member 104 exposed to annulus fluids 42, valve 78 will open permitting passage of tubing fluids 16 through passageway 88, passageway 106, orifice 105, disc passageway 108, conduit 76, gas anchor 2S, tubing perforations 29, into annulus 42.

The unbalanced arrangement of Valve 78 is desirable in that it permits a much more accurate determination and control of the bottom hole pressure in annulus 42. The ratio of the seat area on the tubing side to the seat area on the annulus side can be any desired value preferably from 1:1.1 to 1:10; but the ratio may be outside of this range. The function of the unbalanced valve is the same as that of the balanced valve and that being the passing of about 1 to 100 gallons of tubing fluid to the annulus and then closing.

Operation of the invention with the basic equipment illustrated in FIGURE 1 will now be described. Fluid flows from formation 12 through perforations 14 into casing 10 and thence through perforations 29 into tubing 16 below pump 24. Operation of pump 24 lifts fluid through tubing 16 int-o flow line 18 and through surface pressure relief valve 20. Pressure relief valve 20 is adjusted to a predetermined throttling pressure that will be maintained on pressure switch 22 and registered on gauge 44. The pressure to be maintained at gauge 44 is a function of the weight of the tubing fluid at down hole pressure relief valve 50, tension of down hole relief valve spring 57, and the desired minimum bottom hole pressure in annulus 42. This relationship was explained in the equation number one.

As pump 24 continues to withdraw fluid from annulus 42 and formation 12, it often occurs that the bottom hole pressure in annulus 42 will decrease until an insufficient volume of annulus fluid 54 is available to supply the capacity of pump 24. This condition results in what is known as fluid pounding7 and a substantial reduction in pump efliciency. With the installation of bottom hole pressure relief valve 50 and other components shown in FIGURE 1, this condition is eliminated. When the bottom hole pressure in annulus 42 reaches the minimum desired value, down hole pressure relief valve 50 opens and allows from about 1 to 100 gallons of tubing fluid 56 to pass into annulus 42 thereby suddenly reducing the volume of fluid in tubing 16. The occurence of this action at the bottom of the well is communicated to pressure switch 22 through tubing fluid medium 56 which acting through line 36, control 38 and line 40 terminates the operation of prime mover 34. This stops the pumping action of unit 32, sucker rod 30 and bottom hole pump 24.

When the various down hole and surface components are designed and constructed in accordance with the invention it is practical and desirable to terminate fluid withdrawals from the well when a minimum bottom hole pressure value has been reached.

To illustrate further that aspect of the invention which terminates pumping, assume the following typical well conditions:

Given:

Depth from surface to valve 50 feet 5600 Tubing fluid of specific gravity 0.80 Differential opening pressure of down hole pressure relief valve p.s.i 2000 Tubing seat area/annulus seat area 1:1

Problem:

It is desired that the annulus bottom hole pressure (at the relief valve datum level) be not less than p.s.i.

Solution (from Equation 1):

P=HtiPl-K P1=P+KHt P1=150l2000(5600 0.80 0.433) P1=210 p.s.i.

Therefore by maintaining a well head pressure of 210 p.s.i. with relief valve 20, the down hole pressure relief valve 50 will open when the annulus bottom hole pressure declines to 150 p.s.i. and the pumping operation will be terminated through means previously described.

To illustrate that aspect of the invention that permits measurement of the annulus bottom hole pressure (at valve S0 datum level), assume the same well conditions as before but with an annulus bottom hole pressure (valve datum) greater than 150 p.s.i.

Flow line 18 is blocked downstream from pressure switch 22 and pumping unit 32 operated so that pump 24 continues to bring fluid into tubing 16 thereby increasing the pressure at gauge 44 and bottom hole pressure relief valve 50. If a maximum pressure of 520 p.s.i. (as registered on gauge 44) a sudden pressure drop of gauge 44 is observed, enough data are available to calculate bottom hole pressure since it is known that valve 50 opened at a gauge pressure of 520 p.s.i.

From Equation l:

P=H+P1-K P=1940+5202000 P=460 p.s.i.

Thus it can be seen that by proper selection and design of the components of this invention it becomes possible to select and control a minimum bottom hole pressure on a pumping oil well. Furthermore, by use of the same components it is possible to discern with reasonable accuracy the value of the bottom hole pressure of a pumping oil well. Heretofore these operations have been possible only through the employment of highly delicate and sensitive instruments and usually requiring some form of connecting Wire from the surface to the bottom of the well where the instruments are located and to be operated by highly trained personnel.

Some of the advantages of minimum bottom hole pressure control and bottom hole pressure indicating are listed below:

(1 Prevents iluid pound.

(2) Increases equipment life.

(3) Reduces deposition of minerals on formation by preventing pumping otf.

(4) obtains maximum oil production by maintaining a minimum back pressure on the formation Without pounding uid.

(5) Prevents or decreases tendency of wells heading or flowing off and damaging stuing box packing.

(6) Reduce expenditures or workover and repair service because of more accurate analyses of well problems by having benefit Vof bottom hole pressure information.

(7) Permits more reliable oil reserve estimates by having more bottom hole pressure data.

(8) Affords better control of pressure maintenance flooding because of availability of bottom hole pressure information.

(9) Automatically compensates for changing pump eciency that results from Wear or gas conditions.

(10) Minimizes pump gas locking by assuring a supply of uid when the pump is operated.

(11) Increases the crude oil reserves of an oil well by lowering the cost of producing oil and thereby forestalling the date of economic limit.

The invention is not to be unnecessarily restricted by the details disclosed herein. Various modifications of the disclosed process and apparatus may be made Within the scope and purview of the invention without departing from the same. i

I claim:

1. Apparatus for use in a well comprising in combination a down hole pump sealed in a well tubing by means of a pump seal, said pump having operating means connected therewith; conduit means communicating between uid in said tubing above the pump seal and casing fluid upstream of said pump during pumping; and valve means in said conduit means for opening said conduit means to flow when the bottom hole pressure in said well outside of said tubing is at a selected minimum value and closing said conduit means to flow when said bottom hole pressure is at a higher selected value.

2. The apparatus of claim 1 wherein said valve means comprises a check valve closing toward said pump and having a movable valve element exposed on the pump or tubing side to a relatively small liquid area and on the opposite or casing side to a larger area so as to provide a substantial mechanical advantage in favor of the closed 6 position of said valve and a spring in said conduit means biasing said valve in the closed position.

3. The apparatus of claim 2 wherein the ratio of said small area to said larger area is in the range of 1:1.1 to 1: 10.

4. The apparatus of claim 1 including a tubular housing subjacent and concentric with said pump, said conduit means containing said valve extending through the wall of said housing.

5. The apparatus of claim 4 wherein said valve and conduit means comprise a valve body in the form a spider disposed transversely in said housing and having a iluid passageway extending axially into said valve body, and radially through one of the arms thereof and through the wall of said housing; the entrance to said passageway from inside said housing having a surrounding annular valve seat; a disc across said housing having an annular engaging surface for said seat and conduit means intermediate said engaging surface and the periphery of said disc for passing fluid to and from said tubing; and spring means in said housing coaxial therewith biasing said disc against said seat.

6. The apparatus of claim 1 including a gas anchor subjacent said pump; a tubular valve housing concentric with and surrounding said gas anchor to form an annulus therewith; a transverse closure across said annulus having valve seat and port means therein; an annular seating element below said closure for closing said ports; spring means biasing said element against said seat means to close said port means; and a iluid passageway above said closure from said annulus through the Wall of said housing, said iluid passageway being disposed above said pump seal.

7. The apparatus of claim 1 wherein said conduit means passes through the wall of said tubing above said pump seal.

8. Apparatus in combination with a well extending to a fluid pay Zone comprising a casing and tubing extending from a well head into communication with said pay zone; a down hole pump in said tubing forming an annulus therewith and having pump operating means; a seal between said tubing and said pump closing said annulus; conduit means communicating between fluid in said tubing above said seal and fluid upstream of said pump during pumping; valve means spring biased in the closed position in said conduit means which opens said conduit means to ow when the bottom hole pressure in said well between said tubing and said casing is at a selected minimum value and closes said conduit means to ow when said bottom hole pressure is at a higher selected value; a production line leading from said tubing at the well head having a valve therein and a pressure gauge on the tubing; a pressure switch sensitive to pressure in said line and operatively connected with said pump operating means so as to shut off operation of same when pressure in said line falls below a selected minimum, and a pressure gauge on said tubing.

9. The apparatus of claim 8 wherein said operating means comprises an electric motor operatively connected with a pumping unit attached to a sucker rod on said pump and said pressure switch is electrical and in circuit with the circuit of said motor.

10. A process for terminating the operation of pumping means in a pumping oil Well equipped with a casing and tubing extending from ground level to an oil producing zone which has suicient pressure to cause `oil to rise in the annulus formed between said tubing and casing, there being a bottom hole pump in said tubing sealed therewith and pumping means at the well head, which comprises providing a flow control zone in said well communicating from the uid in said tubing above the pump seal to the uid in said annulus; providing a biased closure in said zone sensitive to differential fluid pressure between said annulus and said tubing at bottom hole level; and regulating a bias on said closure so as to provide a 7 8 selected differential pressure in favor of the tubing pres- 1,720,159 7/ 1929 Willmann 73-302 sure which maintains a predetermined minimum bottom 1,929,451 10/1933 Schmidt 103--179 hole pressure in said annulus during pumping and ter- 2,019,969 11/ 1935 Holmes 103-155 minates the operation of said pump by opening said zone 2,149,602 3/ 1939 Horvath 103-42 to ow when the bottom hole pressure in said annulus 5 2,171,410 8/ 1939 Steele 10S-179 falls below said selected minimum. 2,292,796 8/ 1942 Pyle 103-179 References Cited bythe Examiner OTHER REFERENCES UNITED STATES PATENTS A.P.C., Rodanet, 362,231, May 4, 1943.

1,606,167 11/1926 King 73 302 10 LAURENCE V. EFNER, Primary Examiner.

Claims

1. APPARATUS FOR USE IN A WELL COMPRISING IN COMBINATION A DOWN HOLE PUMP SEALED IN A WELL TUBING BY MEANS OF A PUMP SEAL, SAID PUMP HAVING OPERATING MEANS CONNECTED THEREWITH; CONDUIT MEANS COMMUNICATING BETWEEN FLUID IN SAID TUBING ABOVE THE PUMP SEAL AND CASING FLUID UPSTREAM OF SAID PUMP DURING PUMPING; AND VALVE MEANS IN SAID CONDUIT MEANS FOR OPENING SAID CONDUIT MEANS TO FLOW WHEN THE BOTTOM HOLE PRESSURE IN SAID WELL OUTSIDE OF SAID TUBING IS AT A SELECTED MINIMUM VALUE AND CLOSING SAID CONDUIT MEANS TO FLOW WHEN SAID BOTTOM HOLE PRESSURE IS AT A HIGHER SELECTED VALUE.