US2792709A - Apparatus determining static pressures in pumping wells - Google Patents

Description

May 21, 1957 T. w. BELL ETAL APPARATUS DETERMINING STATIC PRESSURES IN PUMPING WELLS Filed Nov. 24, 1954 2 Sheets-Sheet 1 u n. um

T. w. BELL ETAL 2,792,709

May 21;,1957

APPARATUS DETERMINING STATIC PRESSURES IN PUMPING WELLS Filed Nov. 24, 19454A 2 "snetsfsheet 2 APPARATUS ,DETERMINING STATIC PRESSURES IN PUMPING WELLS Thomas W. Bell, Arcadia, and Howard C. Stone, Bakerstield, Calif., assignors to The Texas Company, New York, N. Y., a corporation of Delaware Application November 24, 1954, Serial No. 470,992

2 Claims. (Cl. 73155) This invention relates generally tto pressure measurement in pumping wells and particularly Vto an apparatus for [determining subsurface static pressures therein.

When low specific gravity, high viscosity crude oils are encountered in pumping wells, subsurface static pressures must be :obtained usually by the use of pressure recording equipment. Due to solution gas `contained in heavy crude oil, sonic fluid level tests give unreliable results.

.'lhe :pressure recorder is generally run on the end of a string ot' solid sucker rods, a slow and costly operation, especially when the rods will not drop freely because of their own weight through the viscous crude oil.

Accordingly, it is an object of -our invention to provide an improved apparatus for obtaining subsurface static pressures in pumping wells which is economical both in time and cost and yet precise.

lt is another object of our invention to provide an improved apparatus for `determining bottom hole static pressures where pump-ing of very viscous crude oil is encountered.

t Still another object of invention is to provide an improved apparatus for determining bottom hole static pressures which is simple in structure and accurate in performance.

These and other objects and advantages of the present invention will be apparent from the following description of a preferred form of the invention and from the drawing in which:

Fig. l is a diagrammatic vertical sectional view of a well to which this invention has been applied;

Fig. 2 is a typical curve on a chart from a pressure recorder used in our apparatus for the determination of the bottom hole pressure;

Fig. 3 shows in detail the pumping structure end of the diagrammatic disclosure of Fig. 1; and

Fig. 4 is a partial sectional view of the crossover check valve.

In accordance with one aspect of the present invention, an apparatus for determining subsurface static pressure in pumping wells is disclosed which permits the measurement thereof by comparison of a balancing pressure of known value with the same.

The manner in which this is accomplished may be understood by referring to the drawings, which, in Fig. 1, discloses a well casing at 10, with a cas-inghead therefor at 11 and suitable outlet at 11a. Production tubing 12 is located annularly within the casing 10, with a tubing head at 13 and outlet therefor at 13a. The tubing head 13 supports a stulng box at 14, through which a series or string of hollow sucker rods 15, joined together, extend, leakage therefrom being prevented by the use of a suitable packing material. These sucker rods actuate a lift pump shown diagrammatically at 16, located at the bottom of the production tubing in the vicinity of perforated liner 19a. The pump is joined to the hollow sucker rods by a perforated coupling including some form of check valve device 17 to prevent flow of well uid into the `string of hollow sucker rods. Operation of the pump by nited States Patent fice means Lof, the. sucker rod string is effected by conventional oil lield methods, including the use of walking beams, etc., andcsince no invention is considered to be involved in this aspect of .the combination, details thereof are not disclosed.

Referring specifically to Fig. 3, there islshown a series of hollow sucker `rods 15 joined to each other by means of couplings, one of which is indicated at 30, the sucker rods having `end .protectors `shown in block form at 31. The bottom sucker rod is joined to a cross-over check valve device 17 at one end thereof, with the other end of the check 'valve `device `being joined to a solid sucker Vrod indicated at 32. The .bottom end of this solid sucker rod 32 in turn` is joined `by a coupling 33 to a deep well lift pump 16, which is adapted to be immersed in the well `fluid to bepumped. This well pump is shown in conventionalized form and 4comprises the pump hold down structure at 34, `whichfis adapted to be `placed in locking position with the lock down pump shoe shown at 16a. This pump comprises an outer shell or working barrel 35 and a-plunger 36, which contains the traveling valve structure at `37. A standing valve structure at 38 is adjacent the bottom of Jthenlift pump. `Appropriate series of openings in the outer shell and plunger are `disclosed at 39.

The pumping `operation may be described briefly as followsrthe lift pump 16 is placed at a depth in the well at which the pump will stay covered by Huid during the pumping operation. The pumping cycle starts with an upward strokeof the sucker rods 15, which pulls the plunger 36 up through theworliing barrel 35. The traveling valve at 37 closes, the standing valve at 33 in the working barrel opens, and fluid enters the working barrel from the well. On a downward stroke of the plunger, the traveling valve opens, the standing valve` closes, and fluid is forced from the working barrel through the plunger into the production tubing 12 through the openings 39. Repeated strokes bring the well uid to the surface through the outlet at 13a, Fig. 2.

IFig. 4 is an enlarged detail of the cross-over check valve device 17. This comprises ends threaded to receive the bottom end of the series of hollow sucker rods at 40 and the top end of the solid sucker rod 32 at 41. The axial bore of the valve device 17 has a valv-e seat at 42 for seating the valve ball 43, which is held in closed or seated position by a bias spring 44, which is adjusted by the spring follower 45, inserted in the end 41 before the solid sucker rod 32 is attached thereto.

The valve device conta-ins perforations which are equally spaced about the circumference, two of which are shown at 46, passing through the wall of the valve device to establish communication with the internal axial bore.

The top of the string of hollow sucker rods is connected to a high pressure gas supply 18, e. g. compressed nitrogen, by means of the line 19, with a high pressure control valve at 20. Manifolded to the gas supply line 19, there is a pressure gage 21, to indicate equilibrium conditions, and pressure recording means at 21a.

During normal pumping operation, the pump is Elocked on the pump shoe indicated at 16a. For subsurface pressure determinations, the pumping is suspended and the pump is raised off the pump shoe, as indicated in Fig. 1, to allow the fluid level, shown at WL in the Well casing 10 and production tubing 12, to equalize in accordance with the subsurface formation pressure. The well is allowed to stand idle so long as considered necessary for the static formation pressure to reach equilibrium conditions before determination of the subsurface static pressure is started.

Then high pressure gas from the supply 18 is injected periodically into the string of hollow sucker rods 15, until the pressure as indicated by the pressure gage 21, manifolded to the supply line 19, reaches equilibrium.

This operation unseats the valve ball 43 and displaces any uid which may have passed into the hollow sucker rods and is depicted in the chart shown in Fig. 2, where that portion of the curve over area A indicates the initial build-up `of the bottom hole pressure, and the portion B, under the curve, indicates the pressure stabilized at the surface with a small volume of gas liowing down the sucker rods.

High pressure gas is injected momentarily several times into the hollow sucker rods and the pressure allowed to reach equilibrium, `in order to assure that well iiuid, which may have yaccumulated in the string of hollow sucker rods, is expelled. This action is indicated at portion C, under the curve, which covers the fast build-up of pressure by increasing the volume of flowing gas from supply 18 and a relatively fast decline to the stabilized pressure; while portion D, under the curve, indicates the gradual decline of the pressure due to leaks in the equipment, and the portion E, under the curve, indicates the bleeding-oli pressure decline. The points indicated at X and Y are the pressures used in the calculation of the bottom hole pressures.

The subsurface pressure at a desired level as obtained by the described procedure, will be equal to the equilibrium pressure indicated by the pressure gage at 21, Fig. l, plus .the computed pressure head exerted by the gas column contained within the hollow sucker rods at that level. Data for such a computation are available from the density of the gas used, the known depth of the spring loaded check valve, 17, below the surface at the desired level, and the pressure recorded by 'the gage at 21, Fig. l.

The pressure measured at the surface by gage 21 can be corrected to the pressure at the bottom of the gas column by using Dices formula, expressed as:

P (at rcheck valve 17 )=P (at surface, Y

gage 21) ex where e equals 2.718 and where G is the density of the pressurized gas;

h is the depth of check Valve 17 below the surface, and

t is the average of the temperatures at the surface and at the depth of the check valve. The constant 53.3 is the same for all gases.

Experiments have shown that the pressure values obtained by the use of hollow sucker rods and corrected by this formula are as accurate as those obtained by running a pressure recorder on solid sucker rods into the well.

Since certain changes may be made in the above described method and apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not limitative.

We claim: Y

l. An apparatus for determining bottom hole static pressure in a pumping well containing low specic gravity,

rhigh viscosity well liuid comprising, in combination,

means for leading off said well fluid extending down into said well, pumping means for lifting said well iiuid through said first mentioned means, a plurality of hollow rods connected to each `other within said rst mentioned means and joined to said pumping means for actuating the same, means for providing high pressure uid connected to said plurality of hollow rods, and means coupled into said rods adjacent said pumping means for controlling the flow of said high pressure fluid and said well uid from said plurality of hollow rods and for preventing reverse flow of well fluid thereinto.

2. In an apparatus for measuring the bottom hole static pressure of a pumping well containing very viscous fluid,

the combination comprising production tubing, means for References Cited in the tile of this patent UNITED STATES PATENTS Browall June 23, 1942 Toth et al. Oct. 17, 1944

Images