US2349164A - Bottom hole intermitter for pumping wells - Google Patents

Description

May 16, 1944.

w. E. GILBERT BOTTOM `HOLL INTERMITTER FOR PUMPING WELLS Figlll Filed July 20, 1942 Tg.' Fig. I

Patented May 16, 1944- UNITED STATES PA.T1-:1\1'1, orificev BOTTOM HOLE INTERMITTER FOR PUMPING WELLS Walton E. Gilbert, Los Angeles, Calif., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application July 20, 1942, SerialNo. 451,641

2 Claims. (Cl. 10S- 203) The present invention relates to apparatus for increasing the output of wells producing oil and gas by pumping, and pertains more particularly to an improved bottom hole intermitter for such wells.

lA. pumping well normally comprises a string of casing, which may be open or closed at the casing head, andra. string of tubing depending within the casing.. 'The tubing string is provided with a pump near its lower end, and the output of said pump is raised to the surface through said tubing string.

In wells producing appreciable amounts of gas together with the oil, it has been customary to vent or withdraw continuously from the annular space between the casingv andthe tubing the gas produced with the liquid and separated therefrom prior to entrance into the pump, whereby it was expected to reduce the back pressure on the producing sand, and to promote the entry of liquid and gas into the well.

However, difliculty is frequently experienced in securing an adequate separation of the gas from the liquid prior to the entry thereof into the pump, which results in a low liquid volumetric elciency ofthe pump operation, and in choking effects due to mist or foam accumulations in the annular .space between the casing and the tubing, which in outlet, as disclosed in the applicants co-pending application, Serial No. 375,140, iiled January 21, 1942, serves to eliminate or minimize the above undesirable effects and to increase the production of oil for a given pump displacement.

However,` such a surface intermitter has a limited eiectiveness, since gas continues to bubble through the oil in the well throughout the intermitter cycle, and when the casing is of relatively large diameter, the velocity of the gas is not effectively reduced when the casing outlet at the surface is closed by the intermitter. ,i

It is therefore an object of the present invention to provide a bottom hole intermitter, whereby the iiow of gas is periodically interrupted at a point in the well below the pump, and the bubbling of gas from below the pump through the oil in the is completely stopped during the periods when said intermitter is closed.

It is also an object of this invention to provide an intermitter comprising a packer surrounding the tubing string and completely shutting off the annular space around said string, the intake of the pump opening to said annular space above said packer, and the fluids from the producing formation being admitted to the pump intake through an intermitting valve arranged below said packer.

It is known that gas may be produced with the oil partly in the form of a gas dissolved therein at the pressures and temperatures prevailing in the formation, and partly in the form of free gas present in the oil in the form of bubbles of varying size.

The proportional amount of dissolved gas which will come out of solution due to pressure drops in Vthe pump, with deleterious effect on liquid volumetric efficiencies, may be minimized by means such'as disclosed in U. S. Letters Patent No. 2,179,481, to C.J. Coberlywherein the oil-gas Vsolution is passed through a restricted orifice of a size controlled by a plunger valve responsive to well conditions, and the gas is released from solution by expansion due to a release of pressure.

However, the Coberly system does not depart materially from established practice in its provision for separating free gas from the oil, and specifically cannot perform the function here disclosed, since the Coberly valve is a slow response valve normally adapted to increase or to decrease the degree of aperture of the expanding orifice, but not to open or close lsaid orifice in the periodical manner of an intermitter.

It is, therefore, a further object of this invention to provide the present intermitter arrangement with a. snap-action valve inherently adapted to assume a totally closed or a totally open position, thereby contributing to a periodical intermitting action.

These and other objects of this invention will be understood from the following description taken with reference to the attached drawing, where Fig. 1 is a diagrammatic cross-section View ,of the present bottom hole intermitter, and Figs.

a lower portion or liner 30 having perforations 32 through which the fluid from the producing formation ows into the space within the casing.

A tubing string l depends within the casing and supports a pump 6, which may be of the reannular` space between the casing and the tubing 55 ciprocating type actuated from the surface by means of a sucker rod string 2 within the tubing, a1though other types such as fluid operated pumps, or centrifuga1 pumps, may be used with equal advantage for the purposes of this invention.

The tubing string I has likewise attached thereto near its lower end a tubing extension 5 surrounding the pump 6. The annular space between the pump 6 and the tubing 5 is in communication with the annular space between the tubing and the casing 8 by means of passages 3.

A packer l0, which may be of the collapsible type, is mounted around the tubing 5, and may be expanded when desired, by means well known in the art, into contact with the casing 8, thus completely separating the annular space between the casing and the tubing into a lower annular space I5 and an upper annular space 1.

The pump 6 is not in communication with the space within the tubing 5, but opens to the upper annular space 1 by means of the intake 9.

The tubing 5 extends to a desired length below the pump 6 and the packer IIB, and is closed at its lower end by a plug 29, having a central bore 21 therethrough.

Afwhicker-bill tubing 3l, extending, for eX- ample, to a level near the bottom of the perforations 32, is in register with said bore and is supported from the lower side of the plug 29.

The plug 29 supports on its upper side a valve assembly member I1, comprising a cylindrical member having a small diameter central bore I8, and enlarged bores I3 and 23 at its upper and lower ends, respectively.

The lower bore 23 is held in screw-threaded attachment with an upwardly extending projection f the plug 29, thus forming within the valve assembly member I1 a chamber which is in communication with the whicker-bill 3I through the orifice, passage or bore 21, and with the annular space between the valve-assembly member and the tubing 5 through a plurality of openings 2i and 24.

The upper bore I3 is closed by a plug II, and forms a chamber holding loading means, such, for example, as a spring i4, compressed between said plug Ii and a cup i6 slidably fitting within the chamber, It will be understood that the essential function of the spring is to load the plunger, or, in other words, to augment'the gravitational force tending to seat the plunger and that this function may be suitably performed by other means such as replacement of the spring by a weight, or simply by a proper' selection of the mass oi the slidable plunger parts. 4

A stem I9 is attached to the cup I6 and passes through the central small bore I8 into the lower bore 23, being attached at its otherend to a plunger or piston 25, slidably ttng within said bore, a certain amount of leakage being permitted between the outer periphery of the plunger 25 and the walls of the bore 23.

The plunger 25 has on its lower face a reduced portion 26 adapted to seat against the valve seat formed by the orifice 21 and to shut off communication between chamber 23 and the fluid tending to enter tubing 5 through the whicker-bill 3|, said plunger being actuated into closing position by the spring I 4.

The particular form of the plunger 25-26 has been shown in Fig. l as effective in giving a uid tight seal between the member 26 and the seat formed by the orice 21. It is, however, clear that other valve arrangements, such as shown in Figs. 2 and 3. can be equally well used. Thus, Fig. 2 shows a valve having a ball member 25a and a separate ball-urging plunger member 25a. Fig. 3 shows a single-diameter plunger member 25a, wherein a fluid-tight seal may be achieved either by precise machining or by using a fluidtight gasket 26h. In all cases, the only operatively essential feature is that the plunger 25 have a diameter considerably larger than that of the orifice 21, through which the pressure differential is applied to the valve, as will be fully explained below.

In operation, the present apparatus is lowered into a well on the tubing I, and the packer I0 is expanded, thus separating the iluid standing in the well into a portion extending from the bottom of the well up to the packer, and a portion extending from the packer up to the surface of the uid, such, for example, as a level A--A.

At the outset, static conditions usually prevail in the well, and there is no differential pressure acting either across the packer IU or the valve assembly I1. The plunger projection 26 shuts the passage 21 by the downward-acting force of the spring' i4, which is applied through the stem I9, since the upward-acting bottom hole or well pressure at the level Yof the valve, acting against the plunger over an eifective area equal to the crosssection of passage 21, is balanced by the equal downward-acting hydrostatic head of the iluid standing up to the level A-A, vsaid head being applied, due to the leakage around the portion 25 of the plunger, to an area equal to that against which the upward pressure is applied.

However, when the pump 6 is started, liquid from the upper annular space 1 is drawn through the pump intake 9 and forced upward through the tubing string I to the surface.

This reduces both the fluid pressure acting at the pump intake 9, and the pressure or head acting downwardly on the seating area of projection 26. k

Since static conditions still prevail in the lower annular space I5, a diierential pressure develops which finally becomes suiicient to overcome the force of the spring I3, thus lifting the plunger 25.

As soon as the projection 26 of the plunger 25 is unseated, the differential pressure, due to the small value of the leakage permitted around the plunger 25, begins to act on the whole lower face oi the plunger 25, which has a much greater area than the projection 26, with the result that the plunger 25 is instantly snapped back to its uppermost or fully open position, driving the fluid above the piston out through the ports 2l,

Vand opening ports 24 to communication with th bore 21.

The differential pressure then causes an upward flow of liquid and gas from the space below the packer through the whicker-bill 3|, bore 2, ports 24, the space within the tubing 5, ports 3, and into the upper annular space 1.

Throughout this portion of the intermitter cycle, the pressure differential maintaining the valve in its open position is the difference between the pressure within the chamber 23, which acts against the lower face of plunger 25, and

the pressure within chamber 5, which acts against its upper face through the ports ZI, said diierence of pressures being due to the pressure drop caused by the uid ow 'through ports 221.

Since this upward ow reaches a peak rcapacity and then diminishes, this pressure differential becomes, after a period of time, less than the downward acting force of the spring I4. The valve then closes, and remains closed until the 'accumulation of pressure in the space below the pacler and the reduction of pressure due to pumping from the upper annular space 'l result in a differential pressure sufficient to unseat again the projection 26.

As an illustrative example, assumingl the initial hydrostatic head at the valve of the fluid standing up to the level A-A to be 400 lbs. per sq. inch acting equally upward and downward on the seated Valve, the force of the spring ill to be 32 pounds when fully extended and 52 pounds when fully compressed, the area of the lower face of plunger 25 to be 4 sq. inches, and the cross-section of passage 21 and projection 26 to be l sq. inch, the valve will not open initially until the fluid pressure acting downward on the seating area of projection 26 has been reduced below 368 lbs. per sq. inch. When, however, the projection 26 is unseated, the plunger will be snapped back to its open position -by the application of the 32 pounds per sq. inch differential pressure to the total lower face of plunger 25, and will remain open, with intercommunicaticn between the throat 2l and the ports 24 until the total upwardly acting differential fluid pressure on the plunger 25 becomes less than (S2/4:0 8

lbs. per sq. inch, at which time the valve will close again.

It will therefore be seen that the valve will remain closed until the diierential pressure acting upwardly on the valve exceeds 32 lbs. per sq. inch, and will remain open until this differential drops below 8 lbs. per sq. inch, thus giving the desired intermitter action. The above values, of course, are given only by Way of example, and the present apparatus may be adjusted to meet any specic well conditions or pressure ranges, for example, by inserting in each case a pre-set spring of the proper compressive force into the chamber i3, and by selecting proper sizes for the plunger 2li-25 and the ports 2| and 2Q of the valve assembly.

When the valve is open, and the lluid comprising oil and free gas emerges through the ports 3, the gas tends to flow upwards, and the upper annular space 'l below the ports 3 and above the packer it serves as a downpass of a gas anchor permitting the gas to separate from the oil before the latter is drawn into the pump intake S. When the valve is open, therefore, the present intermitter and pump combination operates in the conventional manner of a pump equipped with packer-type gas anchor. Under these conditions, the initial percentage of free gas in the liquid and the ilow velocities in the downpass often prevent a satisfactory degree of oil-gas separation.

However, during that portion of the intermitter cycle when the valve is closed, the supply of gas through the ports 3 is cut ofi, and the free gas still remaining in the iluid present in the upper annular space l, both above and below ports 3, tends to ascend through the fluid in said annular space, whereby the amount of free gas entering the pump intake 9 is effectively minimized. Also, during this portion of the intermitter cycle, the reduced gas flow will help to dissipate any accumulations of mist or foam above restrictions, such as tubing catchers, in the annular space between the casing and the tubing, which accumulations tend to create unnecessary back pressures against the producing formations,

and thus to limit rates of iluid entry to the well.

It will be seen from the above that the present invention provides a system for intermittent natural fluid flow through a snap-action valve from a lower space underlying a packer to an upper annular space above said packer, and for production by pumping from said upper annular space, which system increases the eiilciency of the pump, decreases the back-pressure on the producing formation, and frequently makes it practicable to pump from shallower pump settings than those require-d when conventional equipment is used.

I claim as my invention:

1. A bottom hole pressure intermitter system comprising a packer adapted to be set in a well, means comprising a pump for continuously withdrawing well fluid from the space above the packer, a conduit extending through the packer and adapted to deliver the fluid from the space below the packer to the space above the packer,

a cylindrical valve chamber within said conduit, ports in communication between said cham-ber and said conduit, means comprising an oriiice forming a 'valve seat for admitting fluid from the space below the packer into said chamber the diameter of said orifice being substantially smaller than that of said chamber, a valve plunger comprising an enlarged diameter member adapted for loose sliding reciprocation within said chamber and a reduced diameter member adapted to close said valve seat, and adjustably pre-set loading means adapted to urge the reduced member of said plunger into closure with said valve seat against fluid pressure difierentials acting across the valve, whereby the ratio of the pressure differentials at which said valve opens and closes is substantially equal to the ratio of the diameters of the enlarged member of said plunger and of said orifice, respectively.

2. A bottom-hole pressure intermitter system comprising a packer adapted to be set in a well, means comprising a pump for continuously withdrawing well fluid from the space above the packer, a conduit extending through the packer and adapted to deliver the iiuid from the space below the packer to the space above the packer, a cylindrical valve chamber within said conduit, means comprising an orifice for admitting fluid from the space below said packer to said chamber, the diameter of said orifice being substantially smaller than that of said chamber, port means in the walls of said chamber in communication between said chamber and said conduit, valve means comprising a plunger adapted for reciprocation within said chamber between a plunger position below said port means closing said orice and a plunger position above said port means opening said orice, said plunger being adapted for a loose sliding t within said cylindrical chamber, and adjustably pre-set loading means independent of fluid pressures adapted to urge said plunger valve means to close said orice against pressure dilerentials acting on said plunger, whereby the ratio of the pressure differentials at which said orifice is opened and closed by said plunger valve is substantially equal to the ratio of the respective diameters of said plunger and said orifice.

WALTON E. GILBERT.

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