US2965078A

US2965078A - Piston engine unit for submerged operation in wells

Info

Publication number: US2965078A
Application number: US526352A
Authority: US
Inventors: John D Chesnut; James M Carter
Original assignee: Aerojet General Corp
Current assignee: Aerojet Rocketdyne Inc
Priority date: 1955-08-04
Filing date: 1955-08-04
Publication date: 1960-12-20
Anticipated expiration: 1977-12-20

Description

Dec. 20, 1960 J, c s u ETAL 2,965,078

PISTON ENGINE UNIT FOR SUBMERGED OPERATION IN WELLS Filed Aug. 4, 1955 2 Sheets-Sheet 1 E I i INVENTORS JOHN D.CHESNUT u BY JAMES M. CARTER ATTORNEY. 2

2,965,078 PISTON ENGINE UNIT FOR SUBMERGED OPERATION IN WELLS Filed Aug. 4, 1955 Dec. 20, 1960 J. D. CHESNUT El AL 2 Sheets-Sheet 2 PISTON ENGINE UNIT FOR SUBMERGED OPERATION IN WELLS John D. Chesnut, Newport Beach, and James M. Carter,

Pasadena, Calif, assignors to Aerojet-General Corpo- V ration, Azusa, Calif., a corporation of Ohio Filed Aug. 4, 1955, Ser. No. 526,352

1 Claim. (Cl. 121-164) This invention relates to piston engines which are particularly adapted for submerged operation in oil wells or the like, and has for an object the provision of a fuel and combustion system for such an engine wherein the rate of combustion is not subject to, nor affected by, the ambient pressure in which the engine operates.

The invention may be carried out in connection with a conventional piston and cylinder assembly, wherein the piston is adapted to be moved longitudinally in the cylinder by differential working fluid pressure. For this purpose, working fluid will be supplied to the appropriate end of the cylinder for driving the piston and any attached devices in the desired direction.

A feature of the invention resides in the provision of a fuel and combustion system for vaporizing and pressurizing the working fluid, which fuel and combustion system is enclosed in a rigid fuel container, thereby rendering the combustion process independent of the pressures surrounding the engine, such as well submergence pressures.

Still another feature resides in providing a self-combustible fuel in the fuel container. By self-combustible fuel is meant a substance or mixture of substances which contains all the material necessary for the combustion reaction.

An optional feature, which can be utilized if desired, resides in the provision of self-combustible fuels which react to produce heat and only non-gaseous products, whereby the reaction occurs without the development of substantial pressure within the fuel container due to substances produced by the combustion reaction.

These and other features of the invention will be fully understood from the following detailed description and the accompanying drawings, of which:

Fig. 1 is an elevation partly in cross-section of a single stroke piston engine according to the invention;

Fig. 2 is a cross-section taken at line 2-2 of Fig. 1;

Fig. 3 is an elevation partly in cross-section of one form of a double stroke piston type heat engine according to the invention; and

Fig. 4 is an elevation partly in cross-section of another form of double stroke engine.

Referring to the drawings, Fig. 1 shows a heat engine adapted to provide a single unidirectional power stroke. This engine is shown suspended in a well casing 11 from a line 12 payed out from the surface. The engine comprises an outer cylindrical shell 13 which is closed at its upper end by a threaded plug 14 in the form of a conventional wire line socket. The lower end of the socket is provided with an externally threaded boss 15.

A passage 16 extends through the plug 14 to pass the line 12, the leads 17 of which terminate in an electrically ignitable squib 18. This passage is sealed off by a follower plug 19 which is threaded into the upper plug and tightened down so as to compress material in a stuffing box 20. and thereby seal the passage 16.

' The externally threaded boss projects inwardly from the upper plug, and has a dome 22 threaded onto it.v A

. assists Patented Dec. 20, 1960 plate 21 closes the lower end of the boss '15 and serves as a barrier to prevent the passage of flame from dome 22 into the wire line socket. The leads 17 pass through plate 21 through insulated connections 17a. The boss and dome provide a rigid fuel container, within which there is placed a self-combustible fuel charge 23 which comprises a mixture of materials which react with each other to produce heat, and preferably only solid products of reaction. This mixture is self-contained as well as selfcombustible in that all substances necessary for the complete exothermic reaction are contained in the charge itself, and there is no dependence on an external source of materials such as atmospheric oxygen for the combustion process.

A preferred example of such a fuel charge is a sto ichiometric intimate mixture of powdered aluminum metal and powdered ferric oxide, which on ignition reacts according to the following equation:

A barrier 24 is welded into the shell, and has a passage 25 therethrough which supports and connects with an eductor tube 26. The eductor tube stands vertically in a vaporizing chamber 27 which is formed inside the shell between the upper plug and the barrier. The upper end of this eductor tube preferably is formed with an inverted U so as to convey only vapors and no liquids from the vaporizing chamber. The vaporizing chamber is initially filled with some vaporizable liquid 27a such as water or kerosene, which liquid is in contact with the fuel container so that it will be heated by contact with the fuel container wall when the fuel charge is combusted.

A spring-loaded check valve 28 closes the passage from theeductor tube and is mounted at the lower surface of the barrier. This check valve can beset to open at some predetermined pressure. At the bottom side of the barrier, a conventional piston assembly 29 which is afiixed to a push rod 36 is fitted in sliding and closefitting relationship in the shell below the barrier, so that the piston assembly is axially slidable therein, and the push rod extends out of the shell so that it can be connected to some tool. Stops 31 are provided in the shell to limit piston travel.

Fig. 3 shows a heat engine which is adapted for reciprocating movement. This device is shown suspended by a line 32 in a well casing 40, as illustrated in Fig. l,

and has an outer cylindrical shell 41 closed at its upper end by a threaded plug 42 forming a wire line socket. The lower end of plug 42 is also closed by a plate 43 through which the leads 33 from line 32 lead to an electrically ignitable squib 44 in the same manner as Fig. 1. The squib connects with the upper member of a series of interconnected heat supply fuel containers 45 which are conveniently in the form of individual canisters. These canisters are metal boxes which form rigid fuel containers so as to isolate their contents from the effects of ambient pressures. Fins 45a can be provided to aid in heat transfer. Within each of these fuel containers there is provided a self-combustible fuel charge 45b as described above.

These fuel containers are interconnected by short lengths of tubing 46, each of which encloses a length of slow fuse 46a which is ignitable by the fuel charge just above that individual fuse segment.

The fuel containers are Within a vaporizing chamber 47 which is formed within the casing between the plug and a barrier 48 which is welded across the casing at a mid point thereof. The vaporizing chamber thus encloses the fuel containers and a quantity of vaporizable liquid 48a. The liquid 48a makes direct contact with the fuel containers.

The barrier 48 has a passage 49 therethrough to pass an eductor tube 50.

The shell below the barrier is preferably cylindrical and has a piston 54 axially slidable therein with a push rod 55 attached thereto. The push rod leads away from the piston through a lower barrier 56 threaded into the lower end of the casing, where it can be connected to any desired tool. The lower barrier has a central passage 57 to pass the push rod, and a follower plug 58 and stufiing box 59 to seal the push rod with the barrier. The inside of the casing below the piston is vented to the well bore by vents 60 through the wall of the casing. A cylindrical stop 61 surrounds the push rod and extends from the lower barrier upward toward the piston. Within this retainer there is seated a coil spring 62 which is opposed at one of its ends by the piston, and at the other end by the lower barrier.

Fig. 4 shows an embodiment providing for reciprocating piston motion, and which has valving means for directing the pressurized working fluid to the appropriate side of the piston. The double stroke engine is also suspended from a line 63 payed out from the surface which is fastened to a threaded plug 64 integral with the top of an outer cylindrical shell 65 and forming a wire line socket. This shell encloses a vaporizing chamber 66 at the top, within which is placed a quantity of a vaporizable liquid 67. A fuel container 68, which may be a rigid canister as shown is provided in the vaporizing chamber, and encloses a self combustible fuel charge 68a such as has been described above. This fuel charge is provided with ignition means such as a squib 51, which can be tired to ignite the fuel charge by the passage of an electric current through the leads 69.

A barrier 70 separates the vaporizing chamber from a cylinder 71 within which there is a conventional, axially movable piston assembly 72. Depending from the piston there is a piston rod 73 which passes through a lower barrier '74 and has means 73a for tool attachment. A conventional stuffing box 76 can be provided around the piston rod in the lower barrier.

A conduit or vapor line 77 extends from the vaporizing chamber above the liquid level therein to connect with two inlet ports. An upper inlet port 73 is provided through the wall of the shell near the upper end of the cylinder and a lower inlet port 79 pierces the wall of the shell near the lower end of the cylinder. An upper exhaust port 80 pierces the wall of the cylinder above the level of the upper inlet port 78 and a lower exhaust port 31 pierces the same wall at a level below the lower inlet port 79. Within the cylinder 71, and near the top and bottom thereof are provided two

sleeve valves

82, 83. Each sleeve valve comprises a ring making an intimate sliding fit with the inner wall of the cylinder and having sufficient thickness to cover and close either an inlet port or an outlet port, depending on the position in which they are held. Spring catches 84 are provided in pairs, an upper pair being provided with one of its members at a level even with the upper inlet port, and the lower pair having its members similarly disposed opposite the lower inlet and exhaust ports. At the center of each sleeve valve there is provided a spider 85 to which springs or cables 86, 86a may be attached. These springs are attached to the spider at one end, and to the piston at the other. The sleeve valves also have grooves 87 in their peripheries, which can be engaged by the spring catches. Below the lower sleeve valve 83 there is provided a small coil compression spring 88 which fits in a seat 89 in the upper surface of the lower barrier.

The operation of these embodiments will now be described. In the embodiment of Fig. l, the piston is initially moved to its upper position relative to the vaporizing chamber, and the engine is lowered to its working position in the wellcasing. Anydesired tool which can utilize the single straight line thrust of the push rod may be attached to the push rod before the engine 18 lowered into the well. The body of the well tool is intended to be rigidly attached to the shells 13, 41, or 65 so that a differential pressure can be exerted between them without the need for supplying a hold-down device.

When the unit is positioned in the well, a current is passed through leads 17, and the squib is ignited. The intense localized heat of the squib starts the combustion reaction between the aluminum and the ferric oxide.

This reaction is exothermic, and heats the walls of the fuel container, which in turn heat and vaporize the liquid. The self combustion processes between the aluminum and ferric oxide produces only substances which are nongaseous at the temperature of the reaction, and no noncondensable gases are produced.

When the pressure within the vaporizing chamber has reached the pre-selected pressure, the check valve will open and the pressurized working fluid, that is, the vapor produced in the vaporizing chamber, can flow through the eductor tube and enter the cylinder above the piston to drive the piston downward with a force which is determined by the differential pressure and the total area of the piston. The piston is driven down until it strikes the limiting stops 31.

This is not a reciprocating device, and its usefulness is limited to applications requiring but a single stroke. The engine does have the advantage that the conditions within the fuel and combustion system are entirely independent of external conditions, due to their enclosure within the rigid fuel container. It has been found that the isolation of the fuel in this manner is desirable, since the high pressures often encountered in applications such as submergence in oil wells deteriorates the combustion reaction, and causes it to proceed at an undesirable rate. Therefore the combustion unit, by being isolated, is enabled to operate at some optimum rate.

By selecting self-combustible fuels which produce only nongaseous products, the inside of the fuel container will have a substantially constant pressure during the reaction. This is because the small amount of air which may be present will not be sufiicient to exert significant pressure as the inside of the fuel container becomes heated from the combustion reaction. Furthermore, no gases are generated to exert such pressures within the container.

The embodiment of Fig. 3 is adapted for reciprocating operation. However, vapor pressure is exerted only on one side of the piston. In operation, the squib is fired so that the uppermost fuel charge reacts and transfers much of its heat to the surrounding fluid, thereby vaporizing some of it. The vapor escapes into the cylinder through the eductor tube and drives the piston downward to compress spring 62 until the piston hits the retainer 61. This movement also actuates any tool fixed to the rod.

When the piston reaches the bottom of the cylinder, the uppermost fuel charge should be nearly expended. Should it not be so expended, then the additional pressure developed in the vaporizing chamber by the excess fuel will not be utilized by the tool.

When the uppermost fuel charge ceases to generate heat, the vapor will begin to condense in the cylinder, at least partly because of the temperature in the surrounding Well. At the conclusion of the reaction of the uppermost fuel charge, the segment of slow fuse between the first and second fuel charges becomes ignited, and burns slowly toward the second fuel container while the vaporizing chamber cools and the piston is returned to its upper position by the spring 62.

During this return the vapor and condensed liquid in the cylinder will be returned through the eductor tube. If the unit is properly designed, the piston will have been returned to its upper position by the spring 62 and by the pressure exerted by well fluid admitted through the ports 60, by the time the next fuel charge is fired by the slow fuse, and the sequence is repeated for as many times as there are individual fuel canisters.

The fuel and combustion system in this engine is isolated from ambient pressures in the same manner as that shown in Fig. l, and with the same results.

The double stroke engine of Fig. 4 is operated by firing the fuel charge within the canister so as to vaporize the liquid within the vaporizing chamber. This vapor then flows into the gas line, and when the piston is at the top of the stroke as shown in Fig. 4, the upper sleeve valve 82 will be forced into its uppermost spring catch. In this position, the sleeve valve covers the upper exhaust port and leaves the upper inlet port open. Also, in this position, the lower spring 86:; has pulled the lower sleeve valve to its upper position where it is retained by a spring catch and closes the lower inlet and opens the lower exhaust. It will now be appreciated that the cylinder above the piston is fluidly connected to the vaporizing chamber, and that the cylinder beneath the piston is fluidly connected with the well bore. Therefore when the pressure in the vaporizing chamber is greater than the wells submergence pressure the piston is caused to move downward so as to actuate the push rod and any tool connected thereto.

When the piston reaches the bottom of its stroke the spring 86 pulls on the upper sleeve valve so as to overcome the upper spring catch and pull the sleeve valve down to cover the upper inlet and open the upper exhaust. The sleeve valve will be retained in this position by another spring catch. At the same time, the piston will have pushed the lower sleeve valve downward so as to cover the lower exhaust port and leave the lower inlet port open. The lower sleeve valve will be held in this new position by the lower of the spring catches. In this position the cylinder beneath the piston will be connected to the vaporizing chamber, and the cylinder above the piston will be connected to the well bore, and the piston will therefore be moved upward.

When the piston reaches the top of its stroke the spring 86a pulls the lower sleeve valve up to open the lower exhaust port and close the lower inlet port, and the piston will shove the upper sleeve valve upward to close the upper exhaust port and open the upper inlet port.

This succession of events provides a reciprocating motion for the piston, and will continue so long a the pressure in the vaporizing chamber is higher than the well submergence pressure. The fuel and combustion system of this engine is also isolated from ambient pressures in the same manner as that of Fig. 1.

In illustrating several types of systems and engines adaptable to the use of the fuel combustion system of the invention, it is not intended that the invention be limited by any of the described apparatus. The invention com prises a self-combustible fuel and combustion system which is entirely isolated from the effects of ambient pressures. It has been found that the high pressures commonly encountered in oil well bores cause combustion processes to deteriorate rapidly, and devices utilizing conventional submerged and conventional systems have been inetlicient for that reason.

By isolating our fuel combustion system in this manner it is possible to operate the same at optimum conditions to obtain heat energy at the best rate.

This fuel and combustion system will be found advantageous in surroundings where high pressures are encountered, such as in oil well casings. The use of a fuel charge which does not produce gases has the further advantage that the products of the reaction do not themselves contribute to raising the pressure within the fuel container.

This invention is not to be limited to the embodiments shown in the drawings and described in the description which are given by way of illustration and not of limitation, but only in accordance with the scope of the appended claim.

We claim:

An engine unit comprising: a shell forming a chamber and a cylinder below the chamber, said shell having a first barrier thereacross, a piston in the cylinder below said first barrier, a second barrier across the shell below said piston providing a closed fluid chamber between the first and second barriers, a conduit leading from said first-mentioned chamber, a first inlet port connecting with said conduit and providing a flow passage from said conduit into a region of the cylinder between the first barrier and the piston, a second inlet port connecting with said conduit and providing another flow passage from said conduit into a region of the cylinder between said piston and said second barrier, at first vent leading to the exterior of the cylinder from a position in the cylinder between the piston and the first barrier, a second vent in the cylinder positioned between the piston and the second barrier, 21 first sliding valve means within the cylinder at one side of the piston and a second sliding valve means within the cylinder on the opposite side of the piston, first resilient means fixedly attached to the one side of the piston and to the first sliding valve means, and second resilient means fixedly attached to the opposite side of the piston and to the second sliding valve means, whereby reciprocation of the piston slides the firstmentioned valve back and forth between the first vent and the first port and also moves the second-mentioned valve back and forth between the second vent and the second port.

References Cited in the file of this patent UNITED STATES PATENTS 378,663 Davidson Feb. 28, 1888 807,865 Prescott Dec. 19, 1905 870,580 Orr Nov. 12, 1907 880,298 Grant et a1. Feb. 25, 1908 1,916,235 Ruben July 4, 1933 2,429,035 Steving Oct. 14, 1947 2,653,602 Smoot Sept. 29, 1953 FOREIGN PATENTS 15,911 Great Britain July 13, 1906