US3062154A - Well pumping apparatus - Google Patents

Description

Nov. 6, 1962 H. E. WARD 3,062,154

WELL PUMPING APPARATUS Filed July 27, 1959 o o I /36 |6- 0 IA Q FIG. 2

HIS AGENT United States Patent 3,062,154 WELL PUMPING APPARATUS Harold E. Ward, Bakersfield, Califi, assignor to Shell Oil Company, a corporation of Delaware Filed July 27, 1959, Ser. No. 829,801 4 Claims. (Cl. 103206) This invention relates to well pumping apparatus and pertains more particularly to an oil well pumping unit for use in pumping oil wells wherein there is substantial fluid hammer and shock loading on the downhole equipment.

More than three-quarters of all the oil wells in the United States are produced by artificial means, the commonest of which is a reciprocating oil well pump positioned near the bottom of the well or adjacent the producing formation. In many of these wells the downhole equipment, principally the string of production tubing, the sucker rods and the reciprocating pump, is subjected to forces which cause deterioration or break-down at a rate faster than normal. Fluid hammer and shock loading, caused partially by closure of the valves in the pumping apparatus, are factors which contribute to the deterioration of the equipment.

It is therefore a primary object of the present invention to provide a well pumping appartus adapted to be positioned in a well above a reciprocating pump to reduce the fluid hammer and shock loading on the downhole equipment.

As a result of the shocks that occur during the pumping cycle of a reciprocating oil well pump, a number of leaks may occur in the production tubing string either at the threaded joints or due to longitudinal splits in the wall thereof. Additionally, the downhole pump is subjected to greater wear due to expansion and contraction of the pump barrel as the result of these shock loads.

It is therefore another object of the present invention to provide a well pumping apparatus adapted to decrease the shock loading on the downhole equipment so as to reduce the frequency of leaks in the tubing string and to lengthen the life of the pump.

These and other objects of this invention will be understood from the following description taken with reference to the drawing, wherein:

FIGURE 1 is a diagrammatic view, taken partially in longitudinal cross-section, illustrating the apparatus of the present invention when connected to a reciprocating-type pump in a well wherein the pump is being reciprocated by a prime mover located at the surface; and

FIGURE 2 is a diagrammatic view taken in longitudinal cross-section of the pulsation dampening apparatus of the present invention.

Referring to FIGURE 1 of the drawing, a prime mover of a pumping unit is shown positioned adjacent a wellhead 11 on the surface of the earth 12. Extending downwardly from the wellhead 11 is a tubing string 13. A reciprocating-type pumping unit comprising a pump plunger 14, standing valve 15, and traveling valve 16 is fixedly secured in the bottom of the tubing string 13 with a plunger 14 and traveling valve 16 mounted for vertical reciprocating motion therein. it is assumed that the outer surface of the pump plunger 14 is provided with one or more fluid sealing members or swab cups 17 of a type well known to the art for sealing the space between the outer wall of the pump plunger and the inner wall of the oil tubing string.

Fixedly, secured to the top of the pump above the traveling valve 16, as by a threaded rod 18 is a pulsation dampener 21 which is described in greater detail with regard to FIGURE 2. The pulsation dampener 21 comprises an elongated tubular housing in which a piston ice element 22 is mounted for sliding axial movement therein. Preferably, the piston element 22 may comprise a pair of swab cups or rubbers, as illustrated, mounted in back to back fashion and fixedly secured together with the concave portions facing in opposite directions.

At one end of the pulsation dampener 21, one or more ports are provided in communication between the interior of a tubular housing 21 and the space outside. These ports 23 may either pass through the wall of the pulsation dampener or through the closure member 24 which closes the lower end of the dampener. The upper end of the pulsation dampener 21 may be closed in a similar manner by another closure means 25 which is fixedly secured to the top of the dampener in any fiuidtight manher, as by screw threads or welding. Preferably, the top closure means 25 is provided with a charging conduit 26 which is normally closed by a valve 27 which is preferably recessed, as at 28, below the outer surface of the pulsation dampener so that the valve does not rub against the inner wall of the tubing string when the pulsation dampener 21 is reciprocated in said string.

A threaded pin 3d or other suitable connecting means is provided at the top of the pulsation dampener for connecting it to the lower end of a sucker rod string 31, as shown in FIGURE 1. In the event that the fluid ports 23 are provided through the side walls of the pulsation dampener 21, suitable stop means are provided in the interior of the pulsation dampener 21 to prevent the piston element 22 from descending far enough to uncover the ports 23. Thus, while stop means 32 may be fixedly secured to the inner Wall of the pulsation dampener and extend inwardly therefrom, a stop means preferably takes the form of a rod 33 attached to the bottom side of the piston member 22. The length of the rod 33 is such that its lower end will contact the closure means 24 of the pulsation dampener 21 before the uppermost ports 23 are in communication between the space outside the pulsation dampener and the space within the dampener above the piston means 22. In the event that the ports 23 only extend through the bottom closure member 24 of the pulsation dampener, the stop means 32 or 33 may be eliminated. The stop means 32 or 33 may include a shock absorb-er spring 36 to decrease mechanical damage due to pounding the bottom end of the pulsation dampener.

In order to form a more effective seal at all times, a small amount of liquid such as water or oil 34 is placed above the piston element 22 in order to retain the gas under pressure thereabove. Prior to use, the pulsation dampener of the present invention is charged, through charging valve 27 and conduit 26, with a gas such as nitrogen to a predetermined pressure of about 0.4 pound per square inch per foot of depth to which the pump will be run. The charging pressure depends upon the well conditions under which the present apparatus is to be used.

During operation of the pumping well utilizing the present invention, the pulsation dampener 21, after being charged above the piston element 22 with a gas, is connected by means of threaded pin 30 to the lower end of sucker rod string 31, as illustrated in FIGURE 1. The threaded pin 18 on the other end of the pulsation dampener 21 is connected to the top of the pump plunger, after which both elements are lowered by means of the sucker rod string to the bottom or at any predetermined level within the oil tubing string 31. After securing the pump therein in any conventional manner, the sucker rod string 31 is connected to its prime mover 10 and pumping operations are carried out.

During pumping operations, when the well fluid being lifted by the pump plunger 14 fills the tubing string 13 to the top thereof well fluid enters ports 23 and substantially fills the space within the pulsation dampener 21 below its piston element 22. As shocks are imposed on the well fluid during each pumping cycle, the scaling piston member 22 moves up and down inside the tubular body of the dampener 21 to allow the gas in the upper part of the dampener 2 1 to expand or to compress it. The expansion and contraction of the gas in the pressure chamber above the piston element 22 dampens the shocks generated in the fluid and minimizes their detrimental effects on the pumping equipment, primarily the pump and the tubing string. Normally, the pulsation dampener is charged with a gas to the anticipated average operating pressure within the well.

In one test, fluid pound or shocks due to the pumping equipment were found to be severe under a variety of operating conditions including one in which there was 1500 barrels per day gross production, 95% water cut, production being carried out .at a 1530 foot fluid producing level with a 3-inch by 2%-inch pump positioned at 1655 feet and the pumping unit operating with an 80-inch stroke at about 20 strokes per minute. Prior to installing the apparatus of the present invention 11 tubing splits and collar thread leaks occurred in the tubing string within a four-month period. In the seven months after installing the apparatus of the present invention, only one tubing split had occurred. In addition, the loads on the pumping unit had been reduced substantially, with the peak polished rod load being reduced fro-m 9200 pounds to 8000, while the peak torque had been reduced from 178,000 inch pounds to 144,000.

I claim as my invention:

1. A well pumping installation comprising an elongated fluid-filled string of pipe extending from the earths surface down into a well, a reciprocating-type well pump fixedly positioned within said pipe string at a point below the normal liquid level in the well, an elongated tubular pulsation dampener of a diameter less than the inner diameter of the pipe string, the lower end of said dampener being fixedly secured to the movable portion of said pump for reciprocation therewith, fluid port means open at all times through the wall of said pulsation dampener in communication between the space inside thereof and the fluid in the pipe string surrounding said pulsation dampener, movable piston means mounted in said pulsation dampener dividing the pulsation dampener in two chambers one of said chambers being fluidtight and adapted to be charged with a compressible fluid, a sucker rod string affixed at its lower end to the pulsation dampener and extending upwardly through said pipe string to the surface, and prime mover means positioned at the surface and operatively connected to the upper end of said sucker rod string for vertically reciprocating said sucker rod string.

2. A well pumping installation comprising an elongated fluid-filled string of pipe extending from the earths surface down into a well, a reciprocating-type well pump having standing and traveling valves and a plunger, said well pump being fixedly positioned within said pipe string at a point below the normal liquid level in the well, an elongated tubular pulsation dampener of a diameter less than the inner diameter of the pipe string, the lower end of said dampener being fixedly secured to the movable portion of said pump for reciprocation therewith, fluid port means open at all times through the wall of said pulsation dampener in communication between the space inside thereof and the fluid in the pipe string surrounding said pulsation dampener, movable piston means mounted in said pulsation dampener dividing the pulsation dampener in two chambers one of said chambers being fluid:

tight and adapted to be charged with a compressible fluid, a sucker rod string aflixed at its lower end to the pulsation dampener and extending upwardly through said pipe string to the surface, prime mover means positioned at the surface and operatively connected to the upper end of said sucker rod string for vertically reciprocating said sucker rod string.

3. A well pumping installation comprising an elongated fluid-filled string of pipe extending from the earths surface down into a well, a reciprocating-type well pump having standing and traveling valves and a plunger, said well pump being fixedly positioned within said pipe string at a point below the normal liquid level of the well, an elongated tubular pulsation dampener of a diameter less than the inner diameter of the pipe string, the lower end of said dampener being fixedly secured to the movable portion of said pump for reciprocation therewith, a sucker rod string afiixed at its lower end to the pulsation dampener and extending upwardly through said pipe string to the surface, prime mover means positioned at the surf-ace and operatively connected to the upper end of said sucker rod string for vertically reciprocating said sucker rod string, said pulsation dampener comprising an elongated tubular body member closed at both ends, a slidable piston element movably positioned in said body member and dividing said body member into two chamber, one of said chambers being charged with gas, and fluid port means through the wall of said body member in communication between the space outside thereof and the chamber? A on the other side of the piston element.

4. A well pumping installation comprising an elongated fluid-filled string of pipe extending from the earths surface do-wn into a well, a reciprocating-type well pump having standing and traveling valves and a plunger, said well pump being fixedly positioned within said pipe string at a point below the normal liquid level in the well, an elongated tubular pulsation dampener of a diameter less than the inner diameter of the pipe string, the lower end of said dampener being fixedly secured to the movable portion of said pump for reciprocation therewith, a sucker rod string aflixed at its lower end to the pulsation dampener and extending upwardly through said pipe string to the surface, prime mover means positioned .at the surface and operatively connected to the upper end of said sucker rod string for vertically reciprocating said sucker rod string, said pulsation dampener comprising an elongated tubular body member closed at both ends, a slidable piston element movably positioned in said body member and dividing said body member into two chambers, one of said chambers being charged with gas, fluid port means through the wall of said body member in communication between the space outside thereof and the chamber on the other side of the piston element, stop means carried within said body member for limiting the travel of said piston element to prevent escape of gas through said port means, and a liquid seal carried on said piston element within said gas-charged chamber.

References Cited in the file of this patent UNITED STATES PATENTS 858,901 Nagel July 2, 1907 2,172,602 Williams Sept. 12, 1939 2,633,368 Ross Mar. 31, 1953 2,814,462 De Jarnet Nov. 26, 1957 2,815,928 Bodine Dec. 10, 1957 2,838,283 Simmonds June 10, 1958 2,936,860 Peras May 17, 1960

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