US2375578A - Well pump - Google Patents

Description

[May 8, 1945.

H. J. PAN KRATZ WELL PUMP Filed Aug. 22, 1942 INVENTOR HOWARD J. PANKRATZ Patented May 8, 1945 to Phillips Petroleum Company, a corporation of Delaware Application August 22, 1942; Serial No. 455,792 '1 Claim (01. 103-232) My present invention relates to an improvement in pneumatic displacement oil wellpumps.

More specifically, my invention resides inproviding a valve of special. characteristics which enables a pump such as disclosed in by co-pendingv application, now U. S. Patent 2,311,863, granted February 23, 1943, to be started or kicked-off at a much lowerpressure than would .be possible without its use. My invention also has'iurther utility in that it providesmeans for'draining the eduction or producing string of pipe so thatthe same may be pulled out of the well in an empty condition, should such removal became necessary ordesirable for any reason.

.While my invention has particular utility in connection with the particular pump structure referred. toabove, it is also of value in connection with draining the tubing string'of other pumps which are known to the art. It is an object to provide, in a deep well pump, means whereby the kick-off pressure required to begin: normal operation of the pump may be reduced for, any given starting conditions,

It is an object to provide inexpensive and .reliablemeans by which the above result may be obtained.

. It is a further object to facilitate the removal of the eductio-n tube string from wells equipped with pumps of the class described.

Other objects and advantages are to be realized by' thoseskilled in the art from a consideration of thedrawing formingpart of this specification.

In the drawing, in which likenumerals are used to designate like parts,

desired. For the present purposes, suflice it to say that the pump i2 is nttedwith a perforated bull plug I4 through which fluid in the well reser- 'voir reaches the pump, via. a standing check valve l5 and accumulation chamber I6. The tail pipe I! is a continuation of tubing 13. The working parts of the pump consist of a multi-ported valve rotor (not shown) within the valve stator l8. In operation, gas suppliedunder pressure in tubing I I, by operation o f'the pump rotor ports, is made to lift the well fluid iromaccumulation chamber Hi to the surface via tubing l3. The fluid is lifted in successive slugs with alternate slugs of gas therebetween. l

The amount of pressure required to lift the slugs of oil to the surface is proportional to the total head of fluid in tubing 13 at rest. The

total head of fluid will be equal to the sum of the lengthsof the several slugs, including gaseous slugs. For example, the head presented by a- ,hundred slugs having. an average length of two feet will be equivalent to the head of a solid column of i the same fluid only 200 feet in height,

even though the slugs may be distributed over a rise of athousand feet or more. Hence, in wells of considerabledepth, oil may be lifted to .the

Figure 1 is a View of a bore equipped Since the desired elevation of the pump in the with a pump of the class disclosed in my 00- Well bore ay be considerably below the standi pending application previously referred to, and in level of h Oil (as level Figure the which my present improvement is incorporated. t gs H and I3 Will be full of oil to the Figure 2 is an enlarged sectional view of my Samelevelimprovement which is the subject of the present In Order. to in Operation the P p application 1 i is necessary to clear the oil from the annular Figure 3 is a transverse section about the lin Space etween tubing H and I3, so that gas can 3- 3 of Figure 2. I reach epump ports from the annulus as is re- Referring more particularly to the drawing in 5 qulred in the normal operation of the pump. l The Figure 1 is shown a fragmentary view of a well normal manner of c n t e ann us as een bore having the casing l0 and astring of pressure pp Sufiicient g pressure in t n u t bi H having pneumatic pump 2 inserted to force all of the oil through the pump into the therein. A string of rotatable tubing 13 is pron r tubing S g e e e ratio o ruled for operation of the pump and also ior-cono umes per running foot of tubin between the ductingthe produced oil to the surfaceotthe inner n er p n strings (I3 d eground all as described and disclosed in detail in p tiv 'ly) is such h t an excessive head is built myabove mentioned co-pending Patent 231L863, up by displacement into the smaller string and. to which reference should be had if complete to clear the annulus, therefore, require a very details of the pump structure and operation are. great pressure In a certain case within my knowledge, the oil level A-A (Figure 1) was such that a bottomhole pressure of 260 pounds per square inch was developed by the oil standing in the tubing. The ratio of cross-sectional areas of the annulus and of the inner tubing was in excess of '1 to 1. As a result, the oil displaced from the annulus to the center string was over seven times the amount originally contained therein, giving a total head in excess of eight times the original, or ab'out 2100 pounds per square inch. By installing an unloading valve l9 in the tubing I3 (Figure l), the kick-ofi'pressure required to start pumping the well was reduced to less than 500 pounds per square inch. 1

Referring now to Figures 2 and 3, the details of my improvement are to be seen. The body 20 tothe annulus between tubing strings H and I3. 3 In the example cited, it was illustrated that, with vention is advantageous in that it permits the pump to be emptied at a much lower pressure than otherwise would be required.

As before explained, the conventional manner of kicking-off such a pump hasbeen to displace the fluid standing in the Well bore into the inner tubing string l3 by sheer force of pressure applied a volumetric ratio of 7 to 1 between tubing in I strings II and 13, the pressure head developed of my unloading valve may be machined from upon displacing all of the fluid into the smaller "string was eight times the initial head of fluid standing in the well above the pump.

By use of my unloading device, it is now possible and entirely practical to clean the pump annulus by applying pressure to thesmall tubing, forcing all of the fluid into large tubing II, and

y then gas-lifting the fluid to the surface in tubing In the lower end of channel 22 is threaded a bushing 25 having a bore 26. A closely fitted piston-like valve member 21, in channel 22, has a tapered portion 28 adapted to seat on the bore 26. A very light spring 29 is loaded between the back end of piston 21 andthe threaded plug 30, the latter member being provided with a stem portion 3| to prevent collapse or deformation of the spring when compressed. In a portion of the adjacent wall, two ports 32 and 33 are bored in communication with channel 22. l The lengths of stem 3| and piston 21 and the positions of ports 32 and 33 are so proportioned and arranged that piston 21 may travel upwardly in bore 22 far enoughthat piston 21 will be wholly above port 33; that is, piston 21 may lie entirely between ports 32 and 33, in which position both ports will be uncovered. u

The valve being installed in tubing string l3 as shown in Figure 1, its operation will now be described, having reference to the various figures for that purpose.

as desired) be applied through casing II, for the pur ose of lifting the oil in the accumulation chamber 16 to the surface through tubing [3, all as explained previously herein, and as explained in my co-pending application referred to else-.

ing'l i to tubing l3 through pump l2. The pres-.

sure drop in the pump is sizeable; therefore, the

pressure unbalance above and below piston 21 will always act to keep the same closed during normal operation of the pump, and hence the valve has no effect whatever upon such operation.

In kicking-off the pump, however, my inscribed manner.

H by continued application of pressure. In displacing the fluid from the smaller tubing to the larger, the developed pressure headin the example cited would be not eight times the initial head, but only /7 times the initial head. Thus with the 260 pounds per'square inch static bottom-hole pressure observed in the example, the

pressure required to displace all of the fluid into thejlarge tubing would be t 260 or 297 pounds per square inch instead of the 2,080 pounds per square inch required to displace the oil in 'the -other direction,

Upon development of the 297 pounds 'per square inch pressure head required to displace all of the oil. into the outer pipe string, a slight further increase of pressure will begin to gas-lift the fluid in a well-known manner and the outer string of pipe will shortly become emptied offluid, since pressure in the'tubing, being in excess ofthe formation pressure, will keep the standing valve I 5c1osed and thus will prevent any further fluid from entering the tubing from'the Well reservoir.

piston21 begins to rise oropen. Due to the close f t of the piston'in its cylindrical bore 22, only a very small differential pressure is required to lift it above port 33, so' that the fluid in tubing l3 and channel 2i will immediately begin flowing through port 33 to outer tubing ll. Port 32 is provided as an exhaust or-relief so that piston 21 I may rise freely in bore 22.

It is to be understood that spring 29 is to be made so soft or weak that it presents no appreciable resistance to the rise of. piston. 21 when the latter is pressured from below. The

spring 29 is supplied simply to serve as a stabilizer or shock absorber to prevent fluttering or chattering of the piston on its seat in bushing 25 as the valve is lowered into the well through any fluid that might be standing therein when the valve and tubing string l3 are installed. I have tested my device in a well with the spring 29 omitted, and have found that piston 21 remains seated in a satisfactory manner while pumping, the valve being held closed by difference of pressure in tubing I l and i3 alone.

After kicking off the Well in the manner above described, the gas pressure is cut off from tubing 13 and re-applied to outer tubing H for operation of pump min the conventional pre- It is further to be understood that; while the pressure required to gas-lift the oil in the kicking-off operation need only be slightly in excess of 297-300 pounds per square inch in the example cited, somewhat higher pressure is desirable to execute the kick-off operation quickly. This is partly due to the Well-known fact that the slippage in gas-lifting throughan annulus is quite high, and this type of gas-lift operation would be ineflicient for continuoustproduction purposes.

In the test example, a pressure between 400 and 500 pounds per. square inch was found adequate to kick 01f the well; whereas 2100-2200 pounds per square inch was formerly required before installation of the unloading valve. It should be pointed out in this connectionthat gas-lifting the annulus fluid in the manner herein described 5 is practically impossible without the useof my the tubing. 7

It is understood that many variations in structure of my unloading valve may be made within the scope of my invention. Having described the novel utility of my invention as Well as a preferred form of structure for the same, the following sub-joinedclaimis set forth.

I claim: b An unloading. valve scribed comprising a body member having a through passage therein, asecond passage in said body member having one end in communication with thefirst passage at it lower end, an upper port and a lower port communicating between, 1thesecond passage and the outsideof said body v member, a valve seat in said second passage below valve, since the orifice opening in the pump l2 is too small toallow sufficient flow of gas for lifting of the oil could not be had simply by applying pressure to the inner string and passing it 1 through the pump ports to the annulus.

In pulling the inner string of tubing, for purposes of repairing the pump rotor, for example, my valve is useful in that the fluid standing in. the

tubing will automatically be drained into the larger tubing I I. permitting the inner tubing to be pulled dry. The construction of pum 12 is such that the tubing would otherwiselhave to be pulled wet, thus adding to the total weight and positively at all times, and the spring is betboth of said ports and a valve member closing said seat and movable to uncoversaid lower port,

a helical compression spring urging said valve member to said seat and a spacing member ex.-

tending inside saidspring along the axis of said helix a suificient distance toprevent said valve member from covering the upper one ofsaid ports, and to prevent complete compression of said spring whereby. the valve operates freely ter able to resist fatigue than if. it were completely compressed, regardless of the opening pressure. l I

, HOWARD J. PANKRATZ.

to be lifted by the amount of fluid contained in l for the purposes herein de-

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