CA1185119A - Method and apparatus for raising well fluids - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A piston-and-cylinder engine powered by compressed gaseous medium such as air, nitrogen, methane, helium, or hydrogen supplied at up to 20 atmospheres from a plenum via cylinder port to a face of a free piston fixed on a tubular piston rod extending through an end wall, the rod being connected to the piston of a reciprocating double-acting piston/cylinder pump raising a well fluid. A gas-distribution valve has an actuator rod formed with a shoulder which is pushed by the engine piston near the end of a stroke to energize a spring, and has a slender extension terminated in a head captive in the piston rod which is pulled by the piston near the end of its alternative stroke. At a predetermined piston/end wall clear-ance a trip mechanism frees a rotatable cylindric valve having channels to turn rapidly to a second position from its first position to register channels with valve ports for applying high pressure through a cylinder port approached by the piston, and connecting a low pressure line to the opposite port.
When methane is used, the low pressure line may discharge into the well casing. The high pressure supply is preferably at 500°K
or more and may be delivered by an adiabatic compressor. Up to three pairs of engines may be ganged in aiding relation to drive one pump.
The engine/pump unit is supended at the ends of the tubing leading to surface. The high-pressure line may be insulated.

Description

35~

This invention relates -to pumping apparatus and in particular concerns deep well pumps for raising ear-th fluids such as oil, water, or brines, by means of a compressible driving fluid supplied under pressure from the surface. The invention has special utility for pumping oil by delivering a compressed yas to a submerged reciprocating double-acting deep well pump.
Various prior art methods and apparatus are known for produ-eing petroleum from a formation, such as mechanically-aetua-ted devlees employing a sucker rod connected between a submerged pump and a driving means at the surface. Submerged electric pumps of high volumetric eapaeity are used where allowable rates of produc-tion are high and formation permeability is adequate. Liquid-powered pumps having inherently lower volumetric rates are used for produeing moderate daily flows.
While the aforemen-tioned pumps are in wide use, it is reeog-nized that eaeh type is eharaeterised by disadvantages, such as low energy effieiency (measured as ratio of actual lift work to total work expended), or initial large capital outlay, or high wear rate or difficulties of maintenance. Sucker rod apparatus is subject to rod wear and build-up of deposits, and exhibits decreased efficiency as depth increases particularly for more viscous crudes. Electric-ally driven submerged pumps are complex, subject to burnout, and typically operate with low efficiencies. All liquid-powered pumps require continuous elaborate filtering of the driving liquid, which moreover must be supplied at very high pressures. ~oth electrical and liquid-powered pump systems require highly skilled personnel and elaborate servicing equipment for -their maintenance.

,, It is most desirable -that a continuously operating pumping system should be capable of running for long periods wi-thout down time, and that, as the cost of energy rises, its overall efficiency be high. It is further desirable that componen-ts be simple and that the raising of the pump to the surface for repair, adjustment or maintenance be relatively easy to carry out.

With these concerns in mind, the presen-t invention proposes a gas-powered pumping apparatus having wide versatility and good energy efficiency, comprising a piston and cylinder production pump directly connected with one or more coaxially-aligned double-acting reciprocating piston engines wherein stroking between pred-determined limits is automatically alternated by novel fast-acting valve means.
In its most general expression the invention is realised in a unitary assembly of one or more gas-powered reciprocating piston engines actuating a single-piston oil pump~ the engine or engines together with gas control valves, the oil pump with its control valves, and a check valve, are all housed within an elongated double-walled tubing having an annular space between inner and outer tubes divided by vertical septa to form four parallel sect-oral ducts. The assembly is suspended submerged in the oil or water colu~m andis powered by compressed gas supplied by way of a high-pressure tubing from a surface located compressor, delivering gas at from 5 to about 20 atmospheres pressure, the oil pump piston working against a head which, depending on depth and the specific gravity of the well fluid may range from under 40 atmospheres -to as high as 400 atmospheres, and delivering the fluicl by way of a production tubing to the surface. At the end of each s-troke the ~S~9 compressed gas on the high-pressure side of a gas engine piston is discharged to a low-pressure line for return to the surface.

A~pair of sectoral ducts provide passages for low-pressure oil and high-pressure oil, respectively, while the o-ther two duc-ts serve alternately as high-pressure plenum and low-pressure plenum depending upon whether the gas-engine pistons are moving up or moving down.
For deeper wells, i.e. from about 700 meters to 4500 meters the number of gas engines will be either two, for intermediate depths, or four, or even six, there being an equal number disposed above and below the oil pump for uniform rod loading. In its simplest expresslon, the invention may comprise a single piston-and-cylinder gas engine aboue and connected with a piston-and-cylinder oil pump characterized by slaw downstroke motion and more rap-id~upstroke.
While the earth temperature at depth may be considerably elevated, so that petroleum or other liquids in a formation may be at 350 K or higher, formatlons traversed by a well bore above about 1000 meters depth will have lower temperature. As a consequ-ence crude oil moving upwardly in a production tubing (or in acasing) during a travel time of from a quarter hour to well over one hour tends to be cooled, causing precipitation of dissolved components such as paraffin on metal surfaces as experienced in sucker rod pumping, where deposits must periodically be scraped off.
The present invention provides a pumping system which obviates the problem, by the use of high-pressure gas which is delivered down the well at considerably elevated temperatures, e.g. above 3500K
and preferably approaching 550 K, or even higher, thereby offse-tting s~

the cooling of crude oil by heat loss to the casing. r~hen the high-pressure gas is delivered from an adiabatic compressor operated without hea-t loss or stage cooling, at a pressure such as 8 to 18 atmospheres, -the warming effects of bo-th the high-pressure line leading to the submerged pump assembly and of -the reduced-pressure return line (which may in cer-tain instances be the casing) actuall~y augment the temperature of crudes reaching -the surface.
A further advantage of the use of hot, high-pressure gas is obtained through the significant reduction of absolute viscosity of any crude oil as its temperature rises, which reduction is advantageous when pumping higher-density crudes. Even a small reduction in viscosity effects substantial savings of work of delivery.
The gas engines of the present invention are supplied with high-pressure gas, preferably at elevated temperature, and prefer-ably at nearly the same temperature as it had when supplied from the surface, for reasons which will be undexstood from the following discussion. During the interval commencing when high-pressure gas is introduced into a cylinder space of the one or more gas engines employed, the pressure remains essentially constan-t at a value depending on head loss incurred by flowing down the high-pressure line, through control valve channels, through the high-pressure plenum, and cylinder ports, until the end of the s-troke. There is virtually no expansion of the gas during the working stroke. At the end of the stroke, powered valve means which have been energized during the terminal portion of the stroke are -tripped at a predetermined travel distance of one piston, causing a nearly instantaneous cutoff of the high-pressure supply to one plenum and simultaneous connection of the other plenum to the supply 5~

so that the cylinder spaces previously under the low pressure of the return line are filled with high-pressure gas, reversing the motions of the pistons. The high-pressure plenum is also simult-aneously connected now to the low pressure re-turn line, by way of a gas control valve channel, so that free blow-down of gas contained in cylinder spaces and plenum drops the pressure rapidly.
While sudden release of gas pressure may be expected to cause intense chilling, likely to freeze components such as a movable control valve having channels and ports, and while free uncontrolled expansion of a volume of gas apparently wastes energy which might have been converted to useful work of lifting oil, the apparatus nevertheless achieves important and unique benefits.
Although sharp local cooling occurs for a short time, e.g. from less than a second to a little over one second's auration` in the valve channel and at discharge ports while flow velocity is high, I have discovered that in fact such cooling is highly localized, and has a recurrence interval equal to the time needed for gas engine pistons to complete one stroke,~ for instance, a down stroke or an upstroke, so that the components can be fully re-warmed by heat conduction from structure at high temperature before the next actuation. Furthermore, the kinetic energy of the high-velocity released gas is rapidly converted by impingement of the gas upon the walls of a plenum guiding the return flow, so that its temperature rapidly rises to nearly the temperature of the gas during the work stroke. A further source of heat regain is the phenomenon by which the partly-confined gas in -the low pressure duct is compressed by incoming high-pressure gas.
Even though all potential work is no-t ex-trac-ted from -the compressed gas before it is released to the re-turn line, the simplicity of pump apparatus with at-tendan-t freedom from wear of parts leads to reduced maintenance requiremen-ts.
Yet another advantage is gained from the use of reciproca-ting high pressure gas-powered piston engines in -the pump assernbly when the high-pressure supply is at eleva-ted temperature, in the transfer of useful quantities of heat to the pump structure which is submerged in -the column of crude oil standing in the well. The significant warming of the walls of the pair of duc-ts in which crude oil enters the pump and in which it is expelled to the production tubing, materially lessens the viscosity of the film of crude contiguous to such walls. Inasmuch as the height of the oil column may be short in certain wells, so that intake of the oil may be slow, an increased daily production can be expected as compared with other pumping apparatus not providing warming.
The gas-powered pumping system of the present invention enjoys a urther advantage, in that no packer or seal is required between the freely-suspended pump assembly and the casing with which the well is completed, so that natural gas coming out of solution as crude oil issues into the well may be drawn off from under the well cap and gathered for utilization at the surface.
Moreover, where such natural gas is of adequate purity it may serve as the source of supply of working gas to a considerable number of gas-powered wells in the same field, being released from the engines of each pu~p at low pressure directly into the well casing above the oil column so -that ~ither no return gas line, or only a very short one, is required. In such case the diameters o~ the high-pressure gas supply line and of the oil produc-tion ~ 3~

tubing may be enlarged, -thereby favoring working a-t reducecl head losses. The available cross-section for re-turned natural gas flowing up the casing permits minimal return line head loss.
When the casing pressure under -the well cap is further reduced by drawing off gas at a rate to obtain less than one atmosphere pressure, the head agains-t which released gas flows may be only slightly greater than one atmosphere in the low-pressure plenum.
As compared with known liquid-powered pumping systems in which the re~circulated liquid, usually an oil, mus-t be constantly filtered to ensure reasonably long operating life of the compon-ents, little if any filtering of the working gases which may be employed with the pumping sytem of the present invention is required. Where closed cycle operation is required, as with nitrogen, helium, or hydrogen, very simple and low-cost in-line filters and drlers suffice. Where atmospheric air is used, water vapour should be removed in any suitable way. Natural gas should be scrubbed to remove water vapor, corrosives and condensables, but once purified may be recycled with simple filter and drier devices.
The compressor unit associated with the system may be of any type capable of delivering high-pressure gas at the desired working pressure, which may range from about 5 atmospheres to 15 or more atmospheres depending on depth and losses encountered.
Such unit may be of any type operating with minimal clearance in the case of piston-and-cylinder apparatus, or with a high degree of in-ternal compression in rotary apparatus such as a helical-lobed device. The work performed by the compressor comprises two functions, which are performed-~in sequence:

a) compressing gas from a low intake pressure to a pretermined high pressure, which is attained prior to the end of the motion of a moving member which reduces the gas volume;
b) delivering the compressed gas, essentially at constant pressure, -through a one-way device such as a check valve to -the receiver or supply line.
The work of a) performs no useful work, per se, of liftiny the pumped fluid, while the work of b) represents the equivalent of direct mechanical linkage with the gas-engine pistons, assuming steady flow and pumping condi-tions, and hence represents lift work.
~owever the work of compression achieves high gas -temperature which is advantageous. Compressors operating at nearly aaiabatic process conditions may be employed to provide the high pressure supply, or conventional two- or more s-tage compressors with inter-cooling may be used, provided that prior to delivery of high pressure gas to the pump its temperature is sufficiently raised by suitable heat transfer means. In the interest of simplicity a relatively high-speed, jacketed piston-and-cylinder compressor with nearly zero clearance has merit. Such unit is preferably arranged for closed circuit operation and is sealed from atmosphere to allow no possibility of leakage. Any appropriate drive means such as an internal combustion engine or an electrical motor may be provided.
The required compressor ou-tput pressure and its volumetric capacity may be calculated from the pressure head on the column of fluid at the pump, and from the intended daily well fluid produc-tion in cubic meters, taking into consideration the ratio of surface areas of the gas engine piston end faces and of the oil pump piston end face. Since the latter will of necessity be the lesser area -- ~3 --~ ~s~

for wells deeper than about 100 me-ters, so that ei-ther only two or at most four gas-powered engines will be able to opera-te the oil pump against the column head, the compressed gas volume will be a multip]e of the daily production. For example, in a well of depth 1670 meters where the casing is full of water which requires to be pumped out before oil production can begin, -the required gas pressure expressed in Newtons per square meter (i.e., Pascals) for four gas-powered engines ganged with a single oil piston of end area 0.22 times the area of a gas piston would be:

P = 1670 x 1000 x 9.807 x 0.22 = 9.00773 x 105 Pascals.

For convenience in referring to pressures and pressure drops throughout this specification, the equivalent in standard atmos-pheres (1 Atm. = 101325 Pascals) will be indicated instead, hence the minimum gas pressure in equilibrium with a static column of water for the above example would be 8.89 atmospheres.
A well head gas pressure somewhat greater than 8.89 atmospheres will be required, when the water in the column is moving upwardly, to overcome pressure drop along the high-pressure tubing of length 1670 meters, the pressure loss due to flow in the distribution valve, plenums, orifices, and in the return line to the surface.

The head loss due to flow of water in the production tubing will increase non-linearly with increasing velocity from its static value of about 152 atmospheres, requiring a proportionate increase in gas supply pressure. Those skilled in the art will readily determine for each installation the operating pressure needed -to achieve a given rate of fluid production, and will be aware -that pressure drops in gas flow lines are also a non-linear function of flow velocity, which is determined primarily by the diam~ters of -the lines carrying the flows and their in-ternal surface smoothness.
The pressure drop may be roughly related as the reciprocal of abou-t the 4.8th power of the diameter in meters, so that losses increase extremely rapidly as the diameter is reduced.
Once the casing is free of water and oil is being pumped, the head against which the pump works will be reduced in proportion to the specific gravity of the crude; for example, p~troleum of density 860 kg/m3 will present a static column head a-t the pump oE about 139 atmospheres, although an additional head due to the higher viscosity of the oil will have to be overcome.
The present invention provides pumping apparatus which enables pumping from deep wells at acceptable efficiencies when one of the more mobile gases, namely methane (CH4), helium (He) or hydrogen (H2~ is substituted for air or nitrogen. The lighter gases have lower absolute viscosities and substantially lower densities than air or nitrogen, so that the pressure drop resulting from a flow of such gases at the same pressure and velocity as air along a given line is a fraction of the drop observed for air.
In using methane an important advantage is the possibility of discharging released low-pressure gas from the pump directly into the casing for return therealong to the well head, saving one line, whereas with all other gases a total of three lines extend from the well head to the pump.
Those skilled in the art will further understand that the pumping system can be arranged and operated at either higher or lower gas supply pressures, for example when higher gas pressure is provided flow velocities will be decreased in the high pressure line with attendant reduced pressure drop therealong for a given performance of useful lift work. However -there may be a greater chilling effect upon blow-down of cylinder spaces and low-pressure plenum space which may affect -the stroking if speed is high.
Where casing dimensions limit the diameters of -tubing -that may be used for gas supply, production, and return lines, a greater useful cross-sectional area may be provided by using a con-tinuous extruded or seamless coiled tubing free of connectors along its length for one or more of the lines.
The return flow in a closed system must be carried in relatively larger diameter tubing or pipe because the volume of low-pressure gas flowing per second in the return line is a multipleof the high-pressure gas supply volume. The released gas is in any case at a few atmospheres pressure, but should preferably be under 3~5 or 3 atmospheres, and preferably under 2 atmospheres.
It is further desirable that the temperature of the released low-pressure gas flowing in the return line be above the tempera-ture of oil in the formation, so that heat exchange by convection from the return line to the production tubing will prevent fall of temperature of the oil. A further reason for elevated temperature of released gas is that the ascending gas expands by the phenomenon of reduction of pressure with altitude. It is therefore desirable that the cooling effect of an expansion from, say, 2.5 a-tmospheres to the intake pressure of the compressor should not lower the gas temperature below about 350 K. Depending on initial high pressure of the gas descending in the high-pressure supply line, a substan-tial amount of heat is gained by gravitational compac-tion of -the rela-tively more dense high-pressure gas, especially if it is air or nitrogen, which compaction rnay increase pressure at the pump by more than two atmospheres in 3000 me-terst with significan-t warming.

~s~

SUMMARY STATEMENT OF THE INVENTION

The invention contemplates the provision of a novel double-acting reciprocating piston-and-cylinder engine powered by a compressed gaseous medium supplied to a cylinder space through a two-position gas-di'stribution valve having channeis recessed into its cylindric surface, the valve being rotatable in a sleeve having four ports, of which two are connected, one to a high-pressure supply lline and -the other to a low-pressure line, the third and fourth are connected each to a plenum, one plenum communicating with the cylinder space at one end via a port and the other plenum communicating with the space via a port at the other end, the valve channels registering with the ports to selectively supply high pressure medium to one plenum a-t a first valve position and to -the other plenum at the second valve position, the valve having an actuator element engageably by pushing or pulling by the piston when near either end of its stroke to store energy in a valve drive mechanism, and having a trip mechanism responsive to piston movement to within a close spacing from a cylinder end wall effective to rotate the valve by stored energy to another of its two positions to supply high pressure medium to the port between the piston and the cylinder end wall.
In a principal aspect the invention outlined above proposes a tubular piston rod sliding through a cylinder end wall and a valve actuator rod element having a shoulder engageabl~ by one face of the piston and havina a slender elonga-te ex-tension slidable in the piston rod and having a head end captively retained therewi~hin engageable for pulling by the other face of the pis-ton.

From a further aspec-t the invention may be unders-tood to provide a pump of the reciprocating double-acting type comprised of a cylinder and a piston fixed on the end of -the tubular piston rod and housed in a common caslng with -the engine.
From yet another aspect the invention will be seen to provide a direct-connected pump as stated wherein its piston diameter is reduced as compared with the engine pis-ton.
It is a further aspect of the invention -that the ratio of diameters of the engine piston, the piston rod, and -the pump piston are in the ratio of about 2.2 : 0.518 : 1.00.
In still another aspect the invention proposes that the piston rod extends through the pump cyinder and beyond, and has its end fixed in the piston of a second engine similar to the first and having its cylinder ports connected with the same plenums as are corresponding ports of the first engine.
The invention also embraces embodiments having the high-pressure supply line and the low-pressure return line serving as suspension means for a combined engine/pump unit housed in a common tubular housing and submerged in well fluid for lifting the fluid to the surface.
It is also contemplated that the invention be operated by supplying a gaseous medium at elevated pressure and at elevated temperature from a compressor located at or near the surface.
In a further aspect the invention extends to operation of an engine/pump unit in a well by means of compressed me-thane, -the low-pressure line extending above the column of well fluid and terminating within the well casing for return of methane and solu-tion gas to the well head, and the gas is withdrawn from under -the well ~ ~ ~ 5 ~7 cap to maintain a low casing internal pressure.
In still another aspect the inven-tion will be understood to be embodied in apparatus comprising at leas-t two pairs of engines directly connec-ted with a sinqle pump which is between the intermediate pair of engines.
The invention will now be described in area-ter particular as manifested in preferred embodiments which are illustrated in -the accompanyina drawin~,~s discussed in the followina specification, which is to be read toaether with a perusal of these drawinqs rlRE 1 is an elevational view of a cased well in which a submeraed en~rine/pump unit of the invention is suspendecl.;
~T~U~E 2 i~s ~n elevational view partly in section showina the encsine/7~ump unit of FIr7u~
~IrrJ~E 3 is a schematic represen-ta-tion of functional com~on-ents of 2 system arranaina a pair of drivina enqines with a sinale t pump;
FIr,lJ~E 4 is an assembly ~uide showina arranaenents for viewinc7 of fiaures of drawinq correspondina to ~art of the apparatus of FTr.URE 3;
Flr.URE 5 is an elevational view in section of the upper end of the assembly indicated by FIr-u~E 3-~Ir.U~E ~ is an elevational view in section of valve mechanism-FTr.U~E 7 is an elevational view o-F an enaine piston, piston rod, and valve actuator devices;
~T~UP~ ~ is an eleva-tional view in sec-tion at reduced scale showina 'che valve actuator element displaced at the upper end o-F
the stroke Oc the enaine ~iston-~T~.r7~ 9 is an elevational vie~7 ~artly in section showina 5~

the aas distribution valve ~nd sleeve por-ts in one v~lve position;
FI~U~E 10 is a view sinilar to FI~.UR~ 9 showin~ the valve displaced to its second Position;
FI~U~E 11 is a perspective view partly cut away showina valve channels and ports, and valve release trackway;
.FI~URES 12 throuah 15 are sec-tions taken on dianetral section-ing planes throuqh the valve mechanism of ~Ir-,U~F, 11 respectively at 12--12, 13--13, 14--14, and 15--15;
F~r~u~E 16 is an enlarqed partly cut away perspective view 10 of valve mecllanism in the same position as shown in EIr~t~RE 8; and FIr,URES 17 and 18 are elevational views in sec-tion of a lower pump valve and lower enqine of an assembly including apparatus of FI~,UR~ 5, 6 and 7.
In -the drawin~, a pump assemhly 100 is shown in FIrluRF 1 suspenc'ed in a ~Tell casina 10 ~enetratinq a producin~ earth Forma-tion 11. ~he assembly is suspended by a tubin~ line 12 conveyina a hiah-nressure aaseous medium, which ~ay for example be dry nethane, supplied to the above-around en~ 13 o.f the line via connector 14, and is also carried by a ~roduc-tion tubina 15 which extends above well cap 16 throuqh connec-tor 17. ~. return line 18 is terninated within the casinq when usina methane, if mixina with solution aases is acceptable. P line 19 which taps into the well head provides a means to withdraw solution aas and methane rrom the easinq.
FI~U~ 2 shows apparatus comprisina a reciprocatin~ c~as-powered enqine 20 connected to a sinqle reciprocatinq well pump 21, and is shown without housina or as.sembly devices for simplici-ty.
Ps illustrated, hiah-pressure aas sup~lied from line 12 is beina ~s~

admitted to cylinder space 22 defined by barrel 23, upper end disc 24 and lower end disc 25, throuah upper cylinder porc 26. The free piston 27 is approaching lower disc 25, the lower end of space 22 beinc~ at nearly the pressure o~ aas issuina throuah lower port 28 (not seen in ~I~URE 2) and flowing up throuqh return ~ine 18. A
tubular Piston rod 29 connected to and extendina below -piston 27 has its lower encl fixed in piston 3n of ~u~p 21 clefined by barrel 31, upper end disc 32 and lower end disc 33.
The foot 34 o~ the assembly is provided with an intake openinq 35 havin~ a ball eheek valve 36 adapted to seat on disc 37 and auidedly restrained in cage 38. In the position illustratecd, clescendinq piston 30 is followed by enterina well ~luid, which ~ay be petroleum or connate water or both, flowina up throu~h openin~
35, throuah ~orts 3~ in disc 40 of a lcwer oil control valve 41, through ports a1 o' an upper disc of the control valve, alona a sectoral duct 42 bounded by eoncentric tuhinq 43 and barrel 31, throuc~h ports 44 in disc 45, throuqh side ports 46 in u~per control valve 47, and thence into cylinder space 48 of pump 21 by ports 4') in clisc 45. ~s oil or other well fluid i.s expelled ahead of piston 30, it ~lows axially throucrh ports 50 in clisc 33, throuah the body of valve 41 (to he described later), then laterally throuah side port 51, up throu~h edge ports 52, and into the hiah-pressure well ~luid duct 53 which is on the opposite side of barrel 31 from duct 42. The well fluid is forced upwardly, throuah edae ports 54 in cdisc 32 and throuqh edge ports 55 in dise 25, edqe ports 56 in disc 24, beina directed eventually throu~h a tubina connectors section 58 into production tubinq 15.
he downstroke of engine piston 27, ~ovina under the force of ~l~S~

the aaseous nedium, would proceed until it abut-tea disc 25, since no crank or other mechanical device limits the piston movement;
however, as will be elaborated at a Further point, aas distribution valve mechanism aenerally desianated 57 responds to downward pull of slender rod element 58 captive within -tubular piston rod 29 at a predetermilled clearance clis-tance, which may be a few milli-meters, to abruptly connec-t high-pressure qas supply line 12 to cylinder port 28 (not seen in ~Ir~U~E 2) below the piston, and at the same moment connectina low-pressure return line 18 to upper port 26. The downstroke is thereby terminated and an upward stroke beains as soon as the head imPosed by the static column of fluid .in tubina 15 is overcome. P.s will be made clear at a further point, separate plenums (not seen in FTr7u~ 2) resPectively co~municatina on one side of barrel 23 with port 26 and on the opposite side with ~ort 28, are each selectively connected by valve mechanism 57 with one of the tuhinas 12 and 18.
~ .eferrina to FIr,URE 3 also, wherein functional components are referenced as previously noted, a further embodiment is shown wherein an upper aas-powered engine 20 and a lower engine 20' are connected to drive a single oil pump 21, the arranaement of ducts for gaseous medium and well fluid, and oPerational accessories may be understood from FIr~U~E 1. ~ell fluid, which may be pe-troleum, is delivered above well cap 16 to a produced oil receiver 59 for disposal. Returned gas, which may be nitroaen, helium, or hydro~en where tubinq lP. extends beyond the well caP, is led (where desircl~le) throuah a return qas cooler 60, which mav include suitable .ilterin~
and dryinq capahilities, before delivery to the intake 0c compressor 61 throuah line 62. The output of compressor 61, ~hich may desir-ably aaain be cleansed and dried in unit 63, is delivered to line 12 for a further circui-t throuqh the punpin~ systen. T~Jhere methane gas is dischar~ed into casina 10 and no separate return line is used, a mixture of solu-tion gas and methane is drawn off by tap line 19 from the casinq into gathering unit 6~ for disposal, or even re-use in the pumping system. Provision is made for start-up and maintenance, by utilising a store 68 Erom which gas may be led through valve 65 to the compressor, or -to which gas rnay be delivered under pressure via valve 66 and line 67.
Referring next to the section drawings in elevation, FIGURES
5, 6 and 7, these should be arranged with other figures as indica-ted in vertical order.
In FIGURE 5 the arrangement of tubing connectors section 58 is shown, comprising a closing end disc 69 into which connector 14 is threadedly engaged. A stepped-diameter sleeve 70 is held be-tween disc 69 and lower disc 71, and suitable high pressure seal discs 72, 73 which nay be netallic or a composition material are compr-essed between the sleeve ends and the discs. A barrel 74 oE length e~ual to the sleeve lengih is similarly gripped. A divider 75 integral with the sleeve and barrel separate high and low pressure gaseous medium flows. A ball check valve 76 resiliently caged by spring 77 is alternatively provided, if necessary, seating on ring 78 within sleeve 70. Well fluid enters the sleeve by way of edge ports 79 from sectoral duct 53.
Immeaia~ely below the connectors section as seen in ~IGURE 6 is a tubular valve housing 80 whose upper margin is sealed agains-t disc seal 82 contiguous to the underside of disc 71. A concentric boss 81 of lesser diameter than the disc projects downwardly and is closely engaged by a fixed valve sleeve 82, which is itself closely fitted within a concentric tube 83 whose upper ~xin~ abuts the underside of the disc and is coextensive with the sleeve.
Within valve sleeve 82 a gas distribution valve body 84 is closely fitted rotatably. The inner surface of sleeve 82 and the external surface of cylindrical valve body 84 are highly finished to close tolerances -to minimise or prevent leakage or high-pressure gaseous medium, while allowing free relative rotation. The upper end 85 of valve body 84 is stepped and the step 85 is received within thrust bearing 86.
As will be made apparent from FI~URES 8 through 16, valve body 84 carries channels 86, 87 recessed into its surface, each channel extending around the circumference through an arc greater than 180 but lying in two axially spaced-apart planes. The description will revert to this structure following description of the actuating mechanism of the valve.
The lower end 88 of the valve body 84 is journalled against ; thrust bearing 89, which is in~erposed between a support disc 124 and end 88. Disc 124 is itself held between lower end 90 of the sleeve 82 and a partial sleeve 91 whose lower end 92 abuts disc 93.
A major length portion of valve body 84 has an axial bore 94 exten-ding upwardly and terminating slightly below the valve channels.
Within the bore a torque trans~er rod 95 is freely rota-table, having its uppermost end 96 of reduced diameter. A separate short rod element 97 is spaced from end 96 and of equal diameter therewith, the two rod portions being spaced by a thrust bearing 98. Upper end 99 of element 97 is of still further reduced diameter and is received in a bore 101 recessed upwardly in valve body 84. A
torsion spring 102 comprising a number of turns of a corrosion-resistant spring wire has one end 103 engaged in a longitudinal bore 104 in valve 84 and its other end (not shown) held in torque transfer rod 95. The spring preferably has a high spring constant to ensure rotation of valve body 84 in~sleeve 82. -Prouision of suitable high-temperature lubricant within spaces of the valve mechanism is desirable for low friction and long life of components.
A bore 105 extending upwardly coaxially of torque transfer rod 95 is occupied by an inserted end 106 of energizing bolt shank 107.
In one position as seen from FIGURE 6, the bolt end is retracted downwardly. Integrally formed spiral ridges 108 extend radially outwardly from the shank, and the ridges are threadedly engaged with a complementarily internally grooved nut 109 fixed in the lower end of bore 105. The head end of bolt 107 is of enlarged diameter and is slidably received within the partial sleeve 91.
Torque transfer rod 95 is provided at its lower end 111 with a thrust bearing 112 interposed between a ring 113 and disc 124.
It is to be understood, as will be made clear further on, hhat axial reciprocation of bolt shank 107, which is non-rotatable in bore 105, will cause the torque transfer rod 95 5O be turned by the sliding of spiral ridges 108 in grooves (not shown) of nut 109 effecting winding up of spring 102 (or unwinding). Preferably ~he angular rotation produced is somewhat larger than the angular displacement of the~valve body 84 between its two limit positions and may for example be from 150 to 210 degrees for rotation of valve body 84 between positions 90 apart.
Bolt head 110 is restrained from rotation but is free to slide axially, as best seen in FIGUES 8, 11 and 16, being guided by a slide in the form of a segment of a cylindric shell. The sleeve ~2 has a segmental portion at its lower end cut away, forming an `" 1.~5~L~L9 opening defined by side edges 114, 115 which extend upwardly to an edge 116 which ex-tends circumEerentially at about the mid-length position of torque transfer rod 95. Slide 113 is so shaped and dimensioned that its left and right side edges 117, 118 ride slidingly on edges 114, 115 of the sleeve opening. The slide 113 is fixed on the side of bolt head 110 in any suitable way, as by recessed socketed set screws 119. The axial leng-th of the slide is sufficiently less than the length of the sleeve opening so that the distance behween the upper edge 120 of the slide in its retracted position and the upper edge 116 of the sleeve opening provides room for sufficient upward displacement of torque transfer rod 95 to wind spring 102 through an appropriate angle.
Support disc 124 is provided with a bore 121 sufficient to clear bolt shank 107 for reciprocating movement therethrough.
Fixed on the exterior of valve body 84 adjacent its lower end 88 (see FIGURES 11 and 15) is a protuberance 122 of rectangular section extending radially outwardly a distance less than the thickness of slide 113. In FIGURE 11 wherein slide 113 is shown cut away to reveal a rectangular opening 123, the slide lies- in its retracted position. This trackway 123 is recessed into the inner sur~ace of slide 113 radially outwardly, but penetrating less than the radial thickness of the slide, yet sufficient so that protub-erance 122 is closely freely slidably confined in the trackway.
Side grooves 125, 126 of the trackway are of sufficient width to accomodate the circumferential thickness of protuberance 122, whereas the upper and lower arcuate trackway portions 127, 128 are shown as being wider as measured in the axial direction, correspon-ding to the axial dimensiGn of the protuberance.

~5~

In the retracted position of slide 113 shown in FIGURES 6, 7 and 11, the downward displacement o:E bolt shank 107 has caused torque transfer rod 95 to be rotated coun-terclockwise as viewed looking downwardly axially of valve body 84, so that at the time that upper arcuate trackway portion 127 has descended to the level of protuberance 122, a substantial torque will be exerted urging valve body 84 anticlockwise, which torque is resisted by protuber-ance 122 being restrained within vertical trackway portion 125 .
As shown in FIGURE 11, the protuberance is just at the point of release from the straight ~rackway portion 125, which release can occur after a slight further retraction downwardly of the slide 113.
When released, valve body 84 will be-rotated rapidly by stored -n energy of spring 102 anticlockwise until protuberance 122 abuts the other end of arcuate trackway portion 127, in which position the spring continues to maintain a predtermined torque holding the valve stably.
Referring to FIGURE 8, slide 113 is shown axially displaced toward its upper position corresponding to that in FIGURE 16. The registration of plenum ports and valve channels for the two valve positions corresponding to limit positions of bolt 107 may be understood from FIGURES 9 and 10, which are partial axial diame-~ral sections taken on a sectioning plane rotated 90 degrees from the - plane of FIGURES 6 and 7.
In FIGURES 9 through 15, sectoral ducts 129 and 130, respect-ively connected to low pressure line 18 and high pressure line 12, are shown aisposed diametrically opposite each other exteriorly of tube 83 and terminating in sectoral ring portions 131, 132 sealing their lower ends. The high pressure duct 130 communicates with tube 5~

opening 133 while duct 129 communicates with tube opening 134 diametrically opposite to 133, the openings lying on axes A--A.
The openings extend through sleeve 82 and, as shown in FIGURE 9, in one valve position channels 86 and 87 bypass the sectoral ring portions 131, 132, connecting plenum 135 wi-th duc-t 129 and connec-ting plenum 136 with duct 130, by way of openings 137 and 138 respectively spaced axially from openings 133, 13~. The openings 137, 138 lie along common axis B--B. The connection jus-t described corresponds to the valve body position of FIGURE 11 during the downstroke of engine piston 27 moving under pressure oE gaseous medium in the upper cylinder space.
FIGURE 10 shows a valve body 84 following the release of protuberance 122 allowing rapid rotation into i-ts al-terna-tive stable positlon. Channel 86 now interconnects plenum 135 with high pressure sectoral duct 130 and channel 87 interconnects plenum 136 with low pressure duct 1?9, so that high pressure gaseous medium is supplied through the engine lower port 28 while the medium is released through upper por-t 26. This will tend to lift piston 27, initia-ting the upstroke.
The mechanism for displacing the bolt head 110 by the movement of piston 27 as it approaches the ends of its stroke ei-ther up or down may be understood by~reference to FIGUP~S 7, 8 and 16. Piston 27 is shown descending toward end wall 25 within about 6 cm from it.
The upper end 139 of tubular piston rod 29 terminates within bore 140 in the underside of the piston body, intermediate its upper and lower faces 141, 142. A coaxial bore 144 of lesser diameter -than bore 140 opens through piston face 141 and polished slender ac-tuator rod 58 is slidably reciprocable in bore 144, and within piston rod 29. The lower end oE rod g8 termina-tes in a head 1~6 which has ~ 3~

a diameter allowing free sllding within the space 147 inside piston rod 29 but large enough so that it is captive under the piston.
As shown, head 146 abuts the piston adjacent rod end 139 so that slender rod 58 is being pulled down.
Upper end 148 of rod 58 is fixed in the lower end of a valve actuator rod 145, as by threading. The actuator rod terminates at its lower end in a squared end face 150, forming a shoulder.
Valve actuator rod 145 slides freely through bore 149 in disc 24.
which forms the upper end wall of engine 20, moved by piston boss 151.
Piston 27 is seen in FIGURE 8 at its upper position:just beginning to occult upper cylinder port 26 -through which exhaust gaseous medium is being expelled; at this moment the rapid rotation of valve body 84 is initiated, to abruptly raise the pressure in plenum 135 communicating with port 26, and releasing gaseous medium in cylinder space 22 below the engine piston to discharge through lower cylinder port 28 along sectoral plenum 136, and thence through a valve channel to the discharge line.
It will be evident that there is no predetermined upper or lower limit position for piston 27, since slight overshoot is possible, depending on the momentum of moving pistons and rod, although the absolute limit of stroke is naturally when faces 141, 142 come into contact with discs 24 or 25. It will be evident also that should any overshoot occur, a cushion of gaseous medium confined by the narrowing of ports 26 or 28 is provided before a face can meet the end disc. Moreover, the nature of the load, namely the lifting of a high column of well fluid in a tubing, represents a constant load moving at relatively low velocity (usually under on meter per second) so that cutoff of high pressure gas to a piston arrests it promptly.

~s~

Referring now to FIGURE 17, an enlarged scale elevational view of lower oil control valve 41 is shown in detail. The system of ball check valves is to be understood to be duplicated by identical components in an upper control valve 47 (not shown) interposed between upper pump end disc 32 and lower engine end disc 25. The downward extension of pis-ton rod 29, terminating in a piston 227 of lower engine 20', in FIGURE 18, provides that the combined net areas under pressure of gaseous medium are identical and that the pump piston net areas are also identical whether strking up or down.
Lower engine 20' is generally identical with engine 20, except that no valve actuator mechanism is provided, the lower piston being "slaved" to the upper. The piston rod 29 extending below pump piston 30 need not be tubular and may therefore be solid if desired. Components of engine 20' which are identical to those of engine 20 are referenced with numbers which are 200 higher.
In FIGURE 17, assuming upward piston movement, well fluid admitted along a path similar to that described for FIGURE 2 proceeds through opening 35 in foot disc 152, around ball check valve 36 which lifts in cage 38, through edge ports 239 in disc 240 and ascends in sectoral duct 42 through edge ports 39 in disc 40, entering valve inlet port 153. The fluid enters annulus 154 and passes through check valves 155 comprising spring-biased ball valves to enter upper annulus 156. This annulus is bounded by thick sleeve 157 in which disc 158 is sealed. An outlet port 159 in sleeve 157 admits fluid to a tubular passage 160 at one side of sleeve 157 leading to upper annulus 161 above a second set of check valves 162. The latter are held closed in their upper ball seats by pressure of fluid in sectoral duct 53 exerted against their 51~

surfaces, the pressure fluid communicating via outle-t port 51.
The well fluid then flows up through axial passages 50 in end disc 33 into the lower cylinder space of barrel 31. At the same time, well fluid is under pressure in the upper cylinder space 48, and is displaced through the upper oil control valve 47 which is disposed in axially reversed relation to that of valve 41, to discharge through an outlet port (not shown) identical to port 51, finally ascending sec-toral duct 53.
The provision of plural check valves is advantageous in avoiding failures to which sliding or spool types are prone, which may close imperfectly when minute sand grains present in crudes or well fluids obstruct metal parts intended to seal. The use of small diameter hardened balls and hardened sea-ts provides excellent crushing capability so that failures to seal are either wholly obviated or greatly minimised, while wear life is much lengthened.
Referring now to FIGURES 4, 5 and 18, the assembly of the engines, pump, gas distribution valve and actuator mechanism, the oil control valves and intake, into a unitary elongate assembly may be seen to comprise axially stacked units, all enclosed in a single tubular housing 163 providing a smooth exterior. In FIGURE 5 there is shown a thickened upper end 164 having threading 165 formed on its inner surface. The threading is engaged by outer threading 167 on a gland 166 provided at one end with a gripping lug system 168.
The lower end of the gland bears on a gasket 169 pressing a ring seal 170 against end disc 69. As will be seen from FIGURE 18 the lower end of the tubular housing is locked, as by swaging or weldlng, to the undersurface of foot disc 152, at 182. The application of 5~9 torque to gland 166 tensions -the housing and applies uniform, torque-free axial pressure to the barrels and end discs of the units interposed between disc 69 in the tubing connectors section 258 and the foot disc 152. The seals 72, 73, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180 and 181), in descending progression through the several units, are thereby compressed to effect sealing of all ducts and spaces.
While one preferred arrangement for in-terconnecting the units forming assembly 100 has been proposed, it is to be understood that the invention may be practiced using conventional pipe connectors and threaded ends on external tubing bounding the sectoral ducts, employing for example left- and right-handed threading precisely axially located relative to abutting cylinder ends. Other arrangements capable of effecting sealing under the pressures pertaining are well known to those skilled in the art.
Any appropriate means for subdividing the annular space contiguous to tubular housing 143 into sectoral passages, such as integrally welded or bonded longitudinal members 183 may be used.
Alternatively, the sectoral ducts may be formed by forming tubing extending parallel with the assembly into annular cross-sectional form, having openings (not shown) welded to cylinder barrels 23 or 223 at bylinder ports 26 and 28.-The invention is not intended to be limited to embodimentsidentical with those described by way of illustration and teaching, but extends to too apparatus and method variants obviously within the s~ill of the art, which fall within the construction of the appended claims.

Claims (33)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an engine of the reversely-stroking piston-and-cylinder type having a cylindrical shell, first and second closing end walls defining a space, coaxial bores opening through said end walls, a piston reciprocable along said shell and having a coaxial bore, a first and a second rod element extending from opposite faces of said piston, said first rod element comprising a minor length portion slidable through said first end wall and formed with a reduced diameter portion slidably received in said piston bore and having a shoulder, said second rod element comprising a tube term-inating in said piston and sliding through the second end wall and extending therebeyond, said reduced diameter portion terminating in a head captively slidably retained in said tubular rod element, first and second port means opening through said shell respectively proximate the first and the second end walls, a first and a second plenum communicating with said space through respective port means, a first conduit supplying high-pressure gaseous medium, a second conduit containing gaseous medium at low pressure, and stroke-resp-onsive valve means for supplying high-pressure medium to that plenum associated with port means adjacent the piston and for connecting the low pressure conduit with the other plenum, said valve means comprising a distributor element movable between first and second stable limit positions at which high pressure supply is connected respectively with first and second port means, energy-storage means actuatable in a first sense by movement of the first rod element through the first end wall a predetermined distance and actuatable in a second sense when the piston returns the first rod element, and means responsive to termination of said predetermined axial displace-ment for releasing energy to drive said distributor element from one stable limit position to its other stable limit position.

2. An engine as set forth in Claim 1 wherein the distributor element comprises a fixed sleeve disposed adjacent said first end wall remote from said space, first and second pairs of ports opening through the sleeve wall, the ports of each pair being disposed diametrically apart and the pairs being spaced axially apart, means connecting an end of the high pressure conduit with one port of a pair furthest from the first end wall and connecting an end of the low pressure conduit with the other port of said pair, means connecting an end of one plenum with one port of the pair nearest the first end wall and connecting an end of the other plenum with the other port of said pair, the distributor element being a cylinder journalled for rotation in said sleeve between predetermined angular limit positions about 90° apart, and having discontinuous channels recessed into its cylindric surface such that in one limit position the channels are in radial registration with the ports to conduct high-pressure medium into one plenum and to conduct medium from the other plenum to the low-pressure conduit, and such that in the other limit position the connections are reversed.

3. An engine as set forth in Claim 2 wherein the plenums comprise sectoral segmental spaces within a tubular member coaxial with and surrounding said valve means and said engine cylinder, and wherein partial ring members form end walls closing the plenums, said ring members being disposed between said pairs of ports on the exterior of said sleeve.

4. An engine as set forth in Claim 2 wherein said distributor element has a bore opening toward said first end wall and wherein said energy storage means comprise a bolt integral with said first rod element having a head disposed within said bore in said element, the bolt having a shank portion carrying spiral ridges, an axially-restrained coupling tube concentric with said bolt shank and rotatable in said bore having on its inner surface grooving mating with said spiral ridges, said sleeve having a segmental portion removed adjacent said bolt head to form an opening bounded by a pair of wall margins parallel with the sleeve axis, a guide member in the form of a cylindric shell segment fixed on said bolt head slidably reciprocable along said wall margins, whereby movement of said first rod element in one direction effects angular rotation of the coupling tube in one sense and movement in the opposite direction reverses the angular rotation, the angular displacement being greater than 110°, and torsion spring means coaxially of and within the bore of the distributor element and linking said element with said coupling tube whereby rotation of said bolt develops a torque on the element increasing with the rotation.

5 . An engine as set forth in Claim 4, wherein said distributor element carries a key projecting radially outwardly from the surface of the element and said cylindric shell segment carried by said bolt head has a pathway of rectangular plan form recessed into the inner surface of the segment, the pathway comprising a pair of straight parallel side portions spaced apart and a pair of arcuate end portions joining the ends of the side portions, said key engaging said pathway holding said element immovable against said torque when the key occupies a position along either of said side portions corresponding to respective stable limit positions of the element but allowing stored energy in said spring to rotate said element when said cylindric shell segment has been displaced sufficiently so that the key may move along an arcuate end portion of the pathway.

6. An engine as set forth in Claim 5, wherein the rotation of said coupling tube corresponding to displacement of the first rod element through said predetermined distance is at least 120° and sufficient so that torque is maintained pressing said key against the end of said arcuate end portion of the pathway when said element has been rotated to one of its stable limit positions different from its previous limit position, and so that reciproc-ation of said first rod element in either sense maintains said key in contact with the outer perimeter of said pathway until the key is between said end portions.

7. An engine as set forth in Claim 4, wherein the coupling tube has an end portion of reduced diameter extending away from said first end wall and said torsion spring is wound upon said reduced diameter end portion and has one end secured to said coupling tube and its other end secured in said distributor element.

8, An engine as set forth in Claim 3 wherein said sleeve is surrounded by a tubular casing and is held immovable within said casing, said pairs of ports opening also through said casing, and the ends of said casing are closed respectively by said first end wall and by a third end wall adjacent the end of said distributor element remote from said bolt, and said ring portions are integrally joined on the exterior surface of said casing.

9. An engine as set forth in Claim 5 wherein one of said distributor and said sleeve comprise a sintered porous metal body saturated saturated with lubricant and the other comprises a hardened polished steel body, the clearance between the distributor element and the sleeve being such that leakage of gaseous medium between them is minimal.

10, An engine as set forth in Claim 4 wherein said distributor element is journalled for rotation in said sleeve between anti-friction thrust bearings disposed contiguous its ends.

11. An engine as set forth in Claim 3 , wherein the extension of said second rod element is linked to a pump of the reciprocating double-acting piston-and-cylinder type, and wherein said pump is enclosed by said tubular casing, and a pair of sectoral segmental plenums are provided externally of said casing for conducting a liquid to the intake of said pump and for conducting liquid at elevated pressure from the output of said pump.

12. An engine as set forth in Claim 11, wherein said second rod element extends through said pump and extends beyond said pump into a second engine comprising a second cylindrical shell, fourth and fifth closing end walls defining a cylinder space, a second piston reciprocably slidable in said shell, said second rod element terminating in said second engine piston, a second pair of ports communicating between said second cylinder space and extensions of said first and second plenums, whereby said space is connected by respective ports of said second pair to the plenum extensions to drive said second piston in aiding relation to said first engine piston.

13. Pumping apparatus comprising first and second conduits adapted for conveying gaseous medium respectively at elevated pressure and at low pressure, a first and a second cylindric shell, an elongate tubular sectional housing, first and second end walls closing ends of said first shell, third and fourth end walls closing ends of said second shell, said end walls having axially aligned bores, first and second pistons respectively slidably reciprocable in said first and second shells comprising gas engine and pump pistons respectively, a tubular piston rod connecting said pistons and sliding through second and third end walls, first and second ports opening through the first shell wall respectively adjacent the first and second end walls, a first and a second plenum exten-ding axially adjacent said first shell communicating with said shell respectively through said first and second ports, a gas distribution valve disposed beyond said first end wall, a rod element slidable through the first end wall extending within said valve, said rod element having a reduced diameter extension forming a shoulder, a coaxial bore in said first piston having said rod extension slidably received therein, said extension terminating in a head of larger diameter than said bore captively retained within said piston rod, said first piston actuating said rod element recurrently between first and second positions at which said shoulder is respectively a predetermined distance from the first end wall and at the first end wall, means biasing the distribution valve to either of a pair of alternative angular limit positions about 90° apart including a first limit position effecting connection of first and second conduits with first and second ports respectively and a second limit position reversing the connections, and means energizing said biasing means responsive to movement of said rod element to either said first or said second positions effective to switch said distribution valve to its alternative limit position to reverse the direction of movement of said pistons.

14. Pumping apparatus as set forth in Claim 3 or 8 or 13 wherein said end walls comprise thick discs having a marginal annular portion of reduced axial dimension forming a pair of shoulders on opposite sides, and said shells seat under axial pressure on said annular portions closely fitting the shoulders, and wherein the plenums comprise sectoral segmental spaces bounded inwardly by the exterior surfaces of said shells and bounded outwardly by said tubular housing, the lateral boundaries of said plenums comprising axially extending bars integrally joined with said shells and said tubular housing, and wherein said housing encloses said valve means, and wherein said high-pressure and low-pressure conduits are connected respectively with two opposed sectoral segmental spaces on the side of said valve means remote from said first end wall.

15. Pumping apparatus as set forth in Claim 13 wherein said distribution valve comprises a fixed sleeve closely fitted inside said tubular housing adjacent said first end wall, first and second pairs of ports opening through the sleeve wall and the housing, the ports of each pair being diametrically opposite each other and the pairs being spaced axially apart, means connecting an end of the high pressure conduit with one port of the pair furthest from the first end wall and connecting an end of the low pressure conduit with the other port of said pair, means connecting one end of the first plenum with one port of the pair nearest the first end wall and connecting an end of the second plenum with the other port of said pair, a distributor element comprising an elongate cylinder journalled for rotation in said sleeve having two closed-ended channels recessed into its cylindric surface, means limiting rotational movement of the distributor element to a predetermined angular excursion less than 180°, the recesses being radially registrable with said sleeve ports in one limit position to conduct high-pressure medium into the first plenum and low-pressure medium from the second plenum to the low-pressure conduit and being radially registrable with sleeve ports in the other limit position to conduct high pressure medium into the second plenum and low pressure medium from the first plenum to the low-pressure conduit.

16. Pumping apparatus as set forth in Claim 15 wherein said distributor element has a coaxial bore opening toward said first end wall and wherein said valve means comprises energy storage means comprising a bolt integral with said rod element having a head disposed within said bore in said sleeve, the bolt having a shank portion carrying spiral ridges, an axially-restrained coupling tube concentric with said bolt shank and rotatable in said bore having on its inner surface grooving mating with said spiral ridges, said sleeve having a segmental portion removed adjacent bolt head to form an opening bounded by a pair of wall margins parallel with the sleeve axis, a guide member in the form of a cylindric shell segment fixed on said bolt head slidably reciprocable along said wall margins, whereby movement of said rod element in one direction effects angular rotation of the coupling tube in one sense and movement in the opposte direction reverses the angular rotation, the angular displacement being greater than the angular excursion of said distributor element by about 30°to 90°, and torsion spring means coaxially disposed within the bore of the distributor element and linking said element with said coupling tube whereby rotation of said bolt develops a torque on the element increasing with the rotation.

17. Pumping apparatus as set forth in Claim 16 wherein said distributor element carries a key projecting radially outwardly from the surface of the element and said cylindric shell segment carried by said bolt head has a pathway of rectangular plan form recessed into the inner surface of the segment, the pathway compr-ising a pair of straight parallel side portions spaced apart and a pair of arcuate joining end portions, said key engaging said pathway holding said element immovable against said torque when said key occupies a position along either of said side portions corresponding to respective limit positions of the element but allowing stored energy in said spring to rotate said element when said cylindrical shell segment has been displaced sufficiently axially so that the key may move along an arcuate end portion of the pathway.

18. A pumping apparatus as set forth in Claim 17 wherein the rotation of said coupling tube corresponding to displacement of the rod element through said predetermined distance when said shoulder is moved to the first or the second positions is sufficiently greater than the angular excursion of said distributor element so that torque is maintained pressing said key against an end of said arcuate end portion of the pathway when said element has been rotated to a limit position from a previous limit position, and so that reciprocation of the rod element following rotation of the distributor element maintains said key in contact with the outer perimeter of said pathway until the key is between said end portions.

19. Pumping apparatus as set forth in Claim 18 wherein the coupling tube has an end portion of reduced diameter extending away from said first end wall and said torsion spring is wound upon said reduced diameter end portion and has one end secured to said coupling tube and its other end secured in said distributor element.

20. Pumping apparatus as set forth in Claim 13 wherein said pump comprises a bottom intake and flow-actuated control valves, one sectoral segmental space extending along said second shell conveying entering liquid into the pump and an opposed sectoral segmental space conveying liquid delivered from the pump between the second shell and said tubular housing, said space extending beyond said valve means into a third conduit.

21. Pumping apparatus as set forth in Claim 20 wherein the gas engine and the pump are assembled axially within said tubular housing and the housing is closely enclosed by an exterior smooth cylindrical metal jacket, a lower end of the jacket being bonded to the pump intake below the pump and the upper end hermetically enclosing said tubular housing and being axially adjustable to apply compressive stress along said cylindrical shell walls and discs.

22. In a method of raising a well fluid to the surface which comprises driving a piston of a reciprocating double-acting piston-and-cylinder well fluid pump submerged in fluid in a well alternately between upper and lower limit positions by actuating a piston rod extending through an upper end wall of said pump, wherein the means to actuate said piston rod is a gas-powered reciprocating double-acting piston-and-cylinder engine having its piston directly connected with said piston rod and reciprocable between predetermined upper and lower piston limit positions, the engine is supplied with high-pressure gaseous medium led from the surface through a conduit and valve means actuated at the completion of a stroke alternately to opposite sides of the engine piston to displace the piston under constant elevated pressure, and the engine cylinder is discharged abruptly at the termination of a stroke into a second conduit leading to the surface, the improvement wherein the high-pressure gaseous medium is supplied to the engine at an elevated temperature in the range from about 350° Kelvin to about 600° Kelvin.

23. The method of Claim 22 wherein the high pressure gaseous medium is supplied by a compressor at the surface delivering compressed medium to said conduit at a pressure in the range from about 5 to about 20 atmospheres.

24. The method of Claim 23 wherein the gaseous medium is compressed nearly adiabatically from a lower temperature and an initial pressure about one atmosphere and is delivered by a conduit which is at least partly insulated to minimize heat loss along a portion of the conduit extending below the surface to a depth where formation temperature is at least about 315° Kelvin.

25. The method of Claim 24 wherein well fluid is elevated from said pump by way of a production tubing leading to the surface, and the low-pressure gaseous medium return line is not provided with insulation so that heat is exchanged from said return line to the production tubing.

26. The method of Claim 23 wherein the gaseous medium is substantially pure methane and the return line is terminated at a height above the pump sufficient to clear the standing height of well fluid in the casing, and the well casing conducts low-pressure methane exhausted from the engine and the methane is gathered under the well cap at low pressure.

27. The method of Claim 26 wherein the gaseous medium under the well cap is withdrawn at a rate such that the absolute pressure is below one atmosphere.

28. The method of Claims 22 or 25 wherein the high-pressure conduit, the production tubing and the return conduit comprise continuous welded coilable steel tubing.

29. The method of Claims 22 or 26 wherein the high pressure conduit and the production tubing comprise continuous welded coilable steel tubing.

30. Pumping apparatus as set forth in Claim 13 wherein said first piston has a second coaxial bore opening toward said second piston and said second piston has a coaxial bore opening toward said first piston, said piston rod is held rigidly coaxially of and fixed in said opposed bores in said first and said second pistons, one end of said rod terminating intermediate end faces of said first piston, said rod comprising a coaxial bore opening into said bore in said first piston, said coaxial bore extending along a major portion of the length of said piston rod between the first and second pistons and terminating between said pistons adjacent said second piston.

31. Pumping apparatus as set forth in Claims or 30 wherein said piston rod extends through said bore in said second piston and therebeyond and said apparatus comprises a third cylindric shell, fifth and sixth disc end walls having coaxial bores and closing ends of said third cylindric shell and defining a third cylinder space, a third piston having a coaxial bore reciprocable in said third space, the extension of said piston rod extending slidably through said bore in said fifth end wall and held rigidly coaxially of and fixed in and terminating in said third piston, and third and fourth ports opening through the third shell wall respectively adjacent said fifth and sixth end walls and communicating said third cylinder space respectively with the first and second plenums, said first piston and said first cylindric shell comprising a first engine, said third piston and said third cylindric shell comprising a second engine, said engines being coupled with said pump piston in aiding relation.

32. Pumping apparatus as set forth in Claim 13, 20 or 21 wherein said first piston and first cylinder comprise a reciproc-ating double-acting engine, and said second piston and second cylinder comprise a reciprocating double-acting pump, and wherein the internal diameters of said first and second cylindrical shells are in the ratio of about 2.2 to 1, and the diameter of said piston rod is about 0.45 times the diameter of said second cylinder.

33. Pumping apparatus as set forth in Claim 31 wherein the ratio of the internal diameters of said first and third cylindric shells to the internal diameter of the second cylindric shell is about 2.2 to 1 and the diameter of the piston rod is about 0.52 times the internal diameter of the second cylindric shell.