US3727693A

US3727693A - Method and fluid system for moving subsurface well equipment in well tubing

Info

Publication number: US3727693A
Application number: US00208339A
Authority: US
Inventors: G Tausch; F Watkins
Original assignee: Camco Inc
Current assignee: CAMCO INC US; Camco Inc
Priority date: 1971-12-15
Filing date: 1971-12-15
Publication date: 1973-04-17
Anticipated expiration: 1990-04-17
Also published as: GB1351913A

Abstract

A fluid system for running and retrieving subsurface well equipment in a well tubing by fluid flow through a curved entrance tubing without restricting the length of the well equipment. The curved entrance tubing having an inside diameter greater than the inside diameter of the well tubing for transporting a first larger locomotive which carries a second smaller locomotive for movement in the well tubing in response to fluid flow. Releasable engaging means between the larger and smaller locomotive whereby the larger locomotive may transport the smaller locomotive through the enlarged curved entrance tubing but allow the smaller locomotive to move alone in the smaller well tubing. A retaining nipple between the enlarged curved entrance tubing and the well tubing for retaining the larger locomotive while the smaller locomotive travels in the well tubing whereby the larger locomotive is in position to receive the smaller locomotive upon its return. A retrieving mechanism for retrieving the enlarged locomotive from the retaining nipple.

Description

United States Patent Tausch et a1.

METHOD AND FLUID SYSTEM FOR MOVING SUBSURFACE WELL EQUIPMENT IN WELL TUBING Inventors:

Assignee:

Filed:

Appl. No.1

Gilbert H. Tausch; Fred E. Watkim,

both of Houston, Tex.

Cameo, Incorporated, Houston, Tex.

Dec. 15, 1971 US. Cl. ..166/315, 166/77, 166/156 Int. Cl. ....E2lb 23/00, E2lb 23/04, E2lb 43/10 Field of Search ..166/75.70, 77, 153,

References Cited UNITED STATES PATENTS Schramm et al.... Coberly et al. Yetman Primary Examiner-Stephen J. Novosad Attomey-James F. Weiler et al.

[57] ABSTRACT A fluid system for running and retrieving subsurface well equipment in a well tubing by fluid flow through a curved entrance tubing without restricting the length of the well equipment. The curved entrance tubing having an inside diameter greater than the inside diameter of the well tubing for transporting a first larger locomotive which carries a second smaller locomotive for movement in the well tubing in response to fluid flow. Releasable engaging means between the larger and smaller locomotive whereby the larger locomotive may transport the smaller locomotive through the enlarged curved entrance tubing but allow the smaller locomotive to move alone in the smaller well tubing. A retaining nipple between the enlarged curved entrance tubing and the well tubing for retaining the larger locomotive while the smaller locomotive travels in the well tubing whereby the larger locomotive is in position to receive the smaller locomotive upon its return. A retrieving mechanism for retrieving the enlarged locomotive from the retaining nipple.

20 Claims, 4 Drawing Figures PAIEmEn P m 3,727. 693

SHEET 2 UF 2 METHOD AND FLUID SYSTEM FOR MOVING SUBSURFACE WELL EQUIPMENT IN WELL TUBING BACKGROUND OF THE INVENTION It is conventional to run and pull subsurface well equipment from a well tubing and perform other subsurface operations by the use of pump-in piston like devices generally referred to as locomotives. The subsurface equipment is frequently pumped through an entrance loop or curved tubing, a conventional size having a five foot radius. The curved radius of the entrance loop greatly limits the allowable straight length of a given diameter well tool that may freely pass through the loop since the loop is constructed of pipe that is of the same internal diameter as that of the well tubing.

The present invention is directed to providing improvements in a pumping system for moving subsurface well equipment into and out of a well tubing through a curved entrance loop which greatly increases the allowable longitudinal length of a given diameter tool that can pass through the entrance loop whereby many of the tools, valves and other equipment previously designed and proven for use with conventional wireline operations can be used in a pumping system.

SUMMARY The present invention is directed to a pumping system for moving subsurface well equipment through a curved entrance loop into well tubing by providing the curved entrance tubing with an inside diameter greater than the inside diameter of the well tubing whereby well tools of greater longitudinal length may pass through the curved entrance loop. However, the locomotives carrying the well equipment must necessarily be of suitable dimensions that will allow them to be pumped through the tubing. Therefore, it is another object of the present invention to provide a first locomotive having an outside diameter substantially equal to the inside diameter of the enlarged curved entrance loop for movement therein.

And since the enlarged entrance tubing or loop will be larger than the well tubing, the present invention is also directed to providing a second locomotive which may be releasably connected and disconnected from the first locomotive so that the second locomotive may be transported through the entrance loop by the first locomotive and thereafter be disconnected and pumped through the well tubing for transporting the well equipment into and out of the well tubing.

A still further object of the present invention is the provision of a retaining nipple between the enlarged curved entrance tubing and the smaller well tubing that will retain the first larger locomotive adjacent the lower end of the enlarged curved loop when fluid circulation is reversed so that the first locomotive is in position to receive the second smaller locomotive traveling in the well tubing on its return for connection thereto and transporting the smaller locomotive back through the enlarged curved tubing.

Since there is always the possibility that the smaller locomotive traveling in the well tubing or its attached well equipment may become inoperative or stuck and must be fished out of the well tubing, it is a still further object of the present invention to provide means for retrieving the large first locomotive from the retaining nipple if necessary so that fishing or other operations may be performed.

Yet a still further object of the present invention is the method of running subsurface well equipment into a well tubing through an enlarged curved tubing connected to the upper end of the well tubing by releasably connecting a first locomotive sized to be transported through the enlarged tubing to a second locomotive sized to be transported through the well tubing, pumping the first locomotive through the enlarged tubing carrying the second locomotive and well equipment therethrough, releasing the locomotives from each other, retaining the first locomotive adjacent the junction between the enlarged tubing and the well tubing, and pumping the second locomotive in the well tubing thereby carrying the well equipment to the desired location in the well tubing.

The present invention further contemplates the method of retrieving well equipment from the well tubing after the well equipment is connected to the second locomotive by pumping the second locomotive and the well equipment up the well tubing and connecting the second locomotive to the first locomotive and thereafter pumping the first locomotive up the enlarged tubing carrying the second locomotive and the well equipment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational schematic drawing showing one environment in which the present invention may be used, FIG. 2 is an enlarged fragmentary elevational view illustrating the present invention moving a well tool through a curved loop,

FIG. 3 is an enlarged fragmentary elevational view, in cross section, illustrating the releasable connection between the locomotive and the retaining nipple, and shows the locomotives in position for releasing from each other and the connection of the larger locomotive to the retaining nipple, and

FIG. 4 is an enlarged fragmentary elevational view, partly in cross section, illustrating the enlarged locomotive seated in a retaining nipple and being disengaged therefrom by a retrieving tool.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and particularly to FIG. 1, an offshore oil/gas platform generally indicated by the reference numeral 10 is provided to service a well having a tubing 12. It is conventional to run and pull subsurface well equipment to the tubing 12 from the platform 10 through a curved entrance loop or tubing 14 which may include one or more curved portions 16. This is normally accomplished by pumping equipment down and up the tubing 12 by a pair of hydraulic lines (only one of which is shown) by piston like devices normally called locomotives. Normally, the radius of the curved portion 16 is restricted to a particular radius, for example five feet, to reduce space requirements and other problems. However, the 5 foot radius restriction greatly limits the longitudinal length of a given diameter object that may freely pass through the loop 16 as the tubing 14 has been the same internal diameter as that of the well tubing 12.

For example, if a well tubing has a 2 inch internal diameter a well tool having a one and /2 inch outside diameter can only be 15.52 inches long to pass through a 5 foot radius loop. Obviously, this significantly reduces the longitudinal length of various well tools from that which have been used in the past in conventional wireline operations. However, should the curved portion 14 be constructed of four inch internal diameter pipe, a 1% inch O.D. well tool 34.64 inches long can pass through the loop 14.

Therefore, the present invention is directed to providing, as best seen in FIG. 2, a curved entrance tubing or loop 14 having an inside diameter greater than the inside diameter of the well tubing 12 thereby allowing the passage of well tools, for example only, a gas lift valve carried by a conventional setting tool which may pass through the curved tubing 14. Thus, many of the tools, valves and other equipment which have been proven and used in conventional wireline operations can be used in the present pumping system. Of course, the locomotives must generally be of similar dimensions as the tubing through which they are pumped in order that a seal be maintained between the internal diameter of the tubing and the outside diameter of the locomotive for pumping the locomotives through the tubing.

Still referring to FIG. 2, a first locomotive 22 is provided having an outside diameter substantially equal to the inside diameter of the curved tubing 14 for move ment therein by conventional pumping operations.

A second locomotive 24 is provided having an outside diameter substantially equal to the inside diameter of the well tubing 12 for movement in the well tubing 12 in response to fluid flow in the well tubing 12. The second locomotive 24 is releasably connected to the first locomotive 22 and supports additional conventional equipment such as another locomotive 25, weight bars 26, knuckle joint 28 and/or other suitable equipment such as the well tool 20.

The present invention is also directed to providing a method and apparatus for releasably connecting the first locomotive 22 to the second locomotive 24 for carrying the well tool through the curved tubing 14 down to the well tubing 12. Thereafter, the second locomotive 24 is disconnected from the first locomotive 22 and may be pumped down the well tubing 12 as is conventional to perform conventional running and pulling operations as well as other well services. Thereafter, the second locomotive 24 may be pumped uphole through the well tubing 12 and reconnected to the first locomotive 22 and the entire assembly pumped up through the curved tubing 14 to the platform 10.

Referring now to FIG. 3, the structure ofa releasable connection between the first locomotive 22 and the second locomotive 24 is best seen. The first locomotive 22 generally includes a body having a sealing means 32 thereon sized for being propelled through the tubing 14 by fluid movement. A locking dog 34 is pivotally connected to the body by a pin 36. The second locomotive 24 also includes a body 38 having a sealing member 40 thereon sized for coaction with the internal diameter of the well tubing 12 for movement therein in response to fluid flow. The second locomotive 24 includes a groove 42. The first locomotive 22 is positively latched to the second locomotive 24 by the action ofa shoulder 46 of the locking dog 34 coacting with the groove 42 of the second locomotive 24. The locking dog 34 is held in the latching position by a sliding sleeve 48 yieldably urged against the locking dog 34 by a spring 50. Thus, the first locomotive 22 may be pumped through the enlarged curved tubing 14 upwardly or downwardly and carries the second locomotive 24 and any attached equipment when the locking dog 34 is engaged in the groove 42.

Referring to FIGS. 2 and 3, a retaining nipple generally indicated by the reference numeral 60 is provided between the enlarged curved tubing 14 and the Well tubing 12 for retaining the'first locomotive 22 within the lowermost portion of the enlarged tubing 14 when fluid circulation therethrough is reversed so as to keep the first locomotive 22 at the lowermost portion of the tubing 14 so that it is in position to receive the second locomotive 24 on its return up the well tubing 12 for re-engagement with the first locomotive 22 and transportation back through the tubing 14. In addition, the retaining nipple 60 may assist in performing the function of releasing the second locomotive 24 from the first locomotive 22 as well equipment is being 'run into the well tubing 14. The retaining nipple 60 may include a first upwardly directed shoulder 62, a recess 64 therebelow, and a second upwardly directed shoulder 66.

As the first locomotive 22 and second locomotive 24 are pumped down the curved tubing 14 in the well equipment and the second locomotive 24 enters the well tubing 12, and as best seen in FIG. 3, shoulder 68 on the sliding sleeve 48 engages the upwardly directed shoulder 62 of the retaining nipple 60 and prevents further downward movement of the sleeve 48. As the

locomotives

22 and 24 continue downwardly, the

locking dog 34 is released from the control of sleeve 48 and moves out of the groove 42 on the second locomotive 24 thereby allowing the second locomotive 24 and well tool 20 to continue down the well tubing 12.

An outward swing of locking dog 34 is generated by the action of the shoulder 70 on the second locomotive 24 and a second sliding sleeve 72 yieldably urged downwardly by a second spring 74 carried by thebody 30 of the first locomotive 22. And as best seen in the lower portion of FIG. 4, the locking dog 34 moves into recess 64 of the retaining nipple 60 thereby retaining the first locomotive 22 in the retaining nipple 60 in a locked position. The shoulder 76 at the lower end of the sleeve 72 engages the locking dog 34 to retain the locking dog 34 in the recess 64. Further downward movement of locomotive 22 is prevented as shoulder 77 on locomotive 22 contacts shoulder 66 of the retaining nipple 60.

It is to be noted that the first locomotive 22 includes an open bore which is normally blocked when the second locomotive 24 is connected to the first locomotive 22, but which is open when the second locomotive 24 is released, thereby allowing fluid flow through the first locomotive 22 to propel the second locomotive 24 down the well tubing 12. With the first locomotive 22 locked in the retaining nipple 60, flow in either direction through the

tubing

12 and 14 may be generated without moving the first locomotive 22 from the retaining nipple 60. Of course, suitable pressure relieving means may be provided to prevent a hydraulic block between the first locomotive 22 and the second locomotive 24in the lower end of tubing 14 as the second locomotive 24 enters tubing 1.2. Normally, the locomotive seals 32 and 40 will allow passage of sufficient fluid to prevent such blockage, but a port 17 may be provided in the body 30 of locomotive 22 if desired.

And with the second locomotive 24 released from the first locomotive 22 the second locomotive 24 may be moved through the well tubing 12 to conventionally perform the operation of running and pulling subsurface equipment as well as performing other subsurface operations.

When it is desired to return the second locomotive 24 to the surface, it is pumped back up to the first locomotive 22 and the nose 80 of locomotive 24 contacts the lower end 76 of the sleeve 72 oflocomotive 22 moving the sleeve 72 against the spring 74 thereby releasing the locking dog 34 from the recess 64 in the retaining nipple 60. The slidable sleeve 48 is then urged downwardly by the spring 50 and once again rotates the locking dog 34 into the groove 42 on the second locomotive 24 as shown in FIG. 3. Thus, the second locomotive 24 is again connected to the first locomotive 22 and the complete assembly can be pumped up and out of the curved tubing 14.

As previously indicated, the first locomotive 22 is normally stopped and retained in the retaining nipple 60 while the second locomotive 24 is moved through the well tubing 12. However, the smaller locomotive 24- may become inoperative or it or its equipment may become stuck in the well tubing 12 and require the passage of an additional locomotive 24 to be pumped in to fish out the stuck locomotive 24. In that event it is desired to at least temporarily remove the stationary locomotive 22 from the tubing 14 to perform fishing operations.

Referring now to FIG. 4, a retrieving locomotive generally indicated by the reference numeral 81 may be provided having a body 82 and a seal 84 for being pumped down into the tubing 14 so as to engage, unlock, and retrieve the first locomotive 22.

Referring to FIGS. 3 and 4, it is noted that the first locomotive 22 may be provided with an internal recess 73 connected to the sleeve 72. Thus, the retrieving locomotive 81 may include a plurality of engaging fingers 86 carried by the body 82 and urged downwardly by a spring 88 and surrounding a wedge member 90. Thus, as the retrieving locomotive 81 is moved downward toward the locomotive 22, the fingers 86 will contact the upper end of the sleeve 72 and move upwardly against the spring 88 and above the wedge 92 v of the member 90 so as to cam into the recess 73 of the sleeve 72 on the second locomotive 22. The spring 88 will then move the fingers 86 downward where they are wedged tightly in the recess 73. When flow in the tubing is reversed, the retrievable locomotive8l will move upwardly pulling the sleeve 72 upwardly from beneath the latching dogs 34 to remove the dogs 34 from the recess 64. Both

locomotives

81 and 22 are now free for return to the surface through the tube 14.

The method of the present invention is apparent from the description of the foregoing apparatus and includes the method of running subsurface well equipment in a well tubing through an enlarged curved tubing connected to the upper end of the well tubing by releasably connecting a first locomotive sized to be transported through the enlarged tubing to a second locomotive sized to be transported through the well tubing, and pumping the first locomotive through the enlarged tubing thereby carrying the second locomotive and well equipment therethrough, releasing the locomotives from each other and retaining the first locomotive in the enlarged tubing, and pumping the second locomotive in the well tubing to carry the well equipment to the desired location in the well tubing. The method further comprehends retrieving well equipment from the well tubing after connecting the well equipment to the second locomotive by pumping the second locomotive and well equipment up the well tubing, connecting the second locomotive to the first locomotive and pumping the first locomotive up the enlarged tubing thereby carrying the second locomotive and well equipment to the surface.

The present invention, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While a presently preferred embodiment of the invention is given for the purpose of disclosure, numerous changes in the detail of construction and arrangement of parts and steps of the process will readily suggest themselves to those skilled in the art and which are en compassed within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In an apparatus for running and retrieving subsurface well equipment in a well tubing by fluid flow through a curved tubing connected to the upper end of the well tubing, the improvement comprising,

said curved tubing having an inside diameter greater than the inside diameter of said well tubing, and

a retaining nipple between the curved tubing and the well tubing including releasable retaining means for releasably retaining a large locomotive, but allowing the passage of a small locomotive into the well tubing.

2. The apparatus of claim 1 wherein the retaining means includes a recess.

3. The apparatus of claim 1 wherein the retaining means includes,

an upwardly directed shoulder, and

a recess below said shoulder.

4. The apparatus of claim 3 including,

a second upwardly directed shoulder below said recess.

5. An apparatus for running and retrieving subsurface well equipment in a well tubing by fluid flow through a curved tubing connected to the upper end of the well tubing, comprising,

said curved tubing having an inside diameter greater than the inside diameter of said well tubing,

a first locomotive having an outside diameter substantially equal to the inside diameter of the curved tubing for movement in the curved tubing in response to fluid,

a second locomotive having an outside diameter substantially equal to the inside diameter of the well tubing for movement in the well tubing in response to fluid, and

releasable engaging means between the first and second locomotives whereby the first locomotive 8. The apparatus of claim 7 wherein the retaining nipple includes an upwardly directed shoulder and a recess for engaging and actuating the releasable engaging means between the first and second locomotives.

9. The apparatus of claim 8 wherein the releasable engaging means includes,

a groove on the second locomotive,

a locking dog on the first locomotive,

yieldable means on the first locomotive normally holding the dog in the groove but engageable with the shoulder on the retaining nipple for releasing the second locomotive from the first locomotive.

10. The apparatus of claim 8 including,

second yieldable means on the first locomotive acting on the dog in a direction to disengage the dog from the groove and contacting said second locomotive when the locomotives are engaged thereby being inefficientive to move said dog, but actuating the dog into the retaining nipple recess when the second locomotive is released.

11. The apparatus of claim 10 including,

a shoulder on the second locomotive for engaging the second yieldable means when the second locomotive is moved toward the first locomotive for releasing the first locomotive from the retaining nipple and reengaging the second locomotive with the first locomotive.

12. The apparatus of claim 5 wherein the releasable engaging means includes,

a groove on one of the locomotives,

a locking dog on the other locomotive, and

spring means yieldably holding the dog in the groove.

13. An apparatus for running and retrieving subsurface well equipment in a well tubing by fluid flow through an enlarged curved tubing connected to the upper end of the well tubing comprising,

a first locomotive having an outside diameter substantially equal to the inside diameter of the enlarged curved tubing for movement in the curved tubing in response to fluid,

releasable engaging means between the first and second locomotives whereby the first locomotive may transport the second locomotive through the enlarged curved tubing but allowing the smaller 6 second locomotive to move alone in the smaller well tubing.

14. The apparatus of claim 13 wherein the first locomotive includes a longitudinal fluid passageway therethrough which is closed when the first and second locomotives are connected together, but is open when the locomotives are disconnected.

15. The apparatus of claim 13 wherein the releasable engaging means includes,

a groove on one of the locomotives,

a locking dog on the other locomotive, and

spring means yieldably holding the dog in the groove.

16. The apparatus of claim 13 wherein the first locomotive includes a longitudinal passageway therethrough,

a locking dog on the bottom end,

means urging said dog outwardly for engagement with the tubing, and

means urging said dog inwardly for engagement with said second locomotive.

17. The apparatus of claim 16 including,

said means urging said dog outwardly extending upwardly for engagement with a releasing tool for releasing the first locomotive from the tubing.

18. An apparatus for running and retrieving subsurface well equipment in a well tubing by fluid flow through a curved tubing connected to the upper end of the well tubing comprising,

said curved tubing having an inside diameter greater than the inside diameter of said well tubing thereby allowing the passage of well equipment of longer length,

a second locomotive having an outside diameter substantially equal to the inside diameter of the well tubing for movement in the well tubing in response to fluid,

a retaining nipple between the curved tubing and the well tubing including an upwardly directed shoulder and a recess below said shoulder for releasably retaining the first locomotive but allowing the passage of the second locomotive into the well tubing,

releasable engaging means between the first and second locomotives including,

a groove on the second locomotive,

a locking dog on the first locomotive,

first yieldable means on the first locomotive normally holding the dog in the groove but engageable with the shoulder on the retaining nipple for releasing the second locomotive from the first locomotive, and

second yieldable means on the first locomotive acting on the dog in a direction to disengage the dog from the groove and into the recess on the retaining nipple.

19. The method of running subsurface well equipment in a well tubing through an enlarged curved tubing connected to the upper end of the well tubing, comprising,

releasably connecting a first locomotive sized to be transported through the enlarged tubing to a second locomotive sized to be transported through the well tubing,

equipment from the well tubing after connecting the well equipment to the second locomotive comprising,

pumping the second locomotive and the well equipment up the well tubing, connecting the second locomotive to the first locomotive, pumping the first locomotive up through the enlarged tubing carrying the second locomotive and the well equipment.

Claims

1. In an apparatus for running and retrieving subsurface well equipment in a well tubing by fluid flow through a curved tubing connected to the upper end of the well tubing, the improvement comprising, said curved tubing having an inside diameter greater than the inside diameter of said well tubing, and a retaining nipple between the curved tubing and the well tubing including releasable retaining means for releasably retaining a large locomotive, but allowing the passaGe of a small locomotive into the well tubing.

2. The apparatus of claim 1 wherein the retaining means includes a recess.

3. The apparatus of claim 1 wherein the retaining means includes, an upwardly directed shoulder, and a recess below said shoulder.

4. The apparatus of claim 3 including, a second upwardly directed shoulder below said recess.

5. An apparatus for running and retrieving subsurface well equipment in a well tubing by fluid flow through a curved tubing connected to the upper end of the well tubing, comprising, said curved tubing having an inside diameter greater than the inside diameter of said well tubing, a first locomotive having an outside diameter substantially equal to the inside diameter of the curved tubing for movement in the curved tubing in response to fluid, a second locomotive having an outside diameter substantially equal to the inside diameter of the well tubing for movement in the well tubing in response to fluid, and releasable engaging means between the first and second locomotives whereby the first locomotive may transport the second locomotive through the enlarged curved tubing but allowing the smaller second locomotive to move alone in the smaller well tubing.

6. The apparatus of claim 5 wherein the first locomotive includes a longitudinal fluid passageway therethrough which is closed when the first and second locomotives are connected together.

7. The apparatus of claim 5 including, a retaining nipple between the curved tubing and the well tubing for releasably engaging and retaining the first locomotive from entering the well tubing but allowing the passage of the second locomotive into the well tubing.

8. The apparatus of claim 7 wherein the retaining nipple includes an upwardly directed shoulder and a recess for engaging and actuating the releasable engaging means between the first and second locomotives.

9. The apparatus of claim 8 wherein the releasable engaging means includes, a groove on the second locomotive, a locking dog on the first locomotive, yieldable means on the first locomotive normally holding the dog in the groove but engageable with the shoulder on the retaining nipple for releasing the second locomotive from the first locomotive.

10. The apparatus of claim 8 including, second yieldable means on the first locomotive acting on the dog in a direction to disengage the dog from the groove and contacting said second locomotive when the locomotives are engaged thereby being inefficientive to move said dog, but actuating the dog into the retaining nipple recess when the second locomotive is released.

11. The apparatus of claim 10 including, a shoulder on the second locomotive for engaging the second yieldable means when the second locomotive is moved toward the first locomotive for releasing the first locomotive from the retaining nipple and reengaging the second locomotive with the first locomotive.

12. The apparatus of claim 5 wherein the releasable engaging means includes, a groove on one of the locomotives, a locking dog on the other locomotive, and spring means yieldably holding the dog in the groove.

13. An apparatus for running and retrieving subsurface well equipment in a well tubing by fluid flow through an enlarged curved tubing connected to the upper end of the well tubing comprising, a first locomotive having an outside diameter substantially equal to the inside diameter of the enlarged curved tubing for movement in the curved tubing in response to fluid, a second locomotive having an outside diameter substantially equal to the inside diameter of the well tubing for movement in the well tubing in response to fluid, and releasable engaging means between the first and second locomotives whereby the first locomotive may transport the second locomotive through the enlarged curved tubing but allowing the smaller second locomotive to move alone in the smaller well tubing.

15. The apparatus of claim 13 wherein the releasable engaging means includes, a groove on one of the locomotives, a locking dog on the other locomotive, and spring means yieldably holding the dog in the groove.

16. The apparatus of claim 13 wherein the first locomotive includes a longitudinal passageway therethrough, a locking dog on the bottom end, means urging said dog outwardly for engagement with the tubing, and means urging said dog inwardly for engagement with said second locomotive.

17. The apparatus of claim 16 including, said means urging said dog outwardly extending upwardly for engagement with a releasing tool for releasing the first locomotive from the tubing.

18. An apparatus for running and retrieving subsurface well equipment in a well tubing by fluid flow through a curved tubing connected to the upper end of the well tubing comprising, said curved tubing having an inside diameter greater than the inside diameter of said well tubing thereby allowing the passage of well equipment of longer length, a first locomotive having an outside diameter substantially equal to the inside diameter of the curved tubing for movement in the curved tubing in response to fluid, a second locomotive having an outside diameter substantially equal to the inside diameter of the well tubing for movement in the well tubing in response to fluid, a retaining nipple between the curved tubing and the well tubing including an upwardly directed shoulder and a recess below said shoulder for releasably retaining the first locomotive but allowing the passage of the second locomotive into the well tubing, releasable engaging means between the first and second locomotives including, a groove on the second locomotive, a locking dog on the first locomotive, first yieldable means on the first locomotive normally holding the dog in the groove but engageable with the shoulder on the retaining nipple for releasing the second locomotive from the first locomotive, and second yieldable means on the first locomotive acting on the dog in a direction to disengage the dog from the groove and into the recess on the retaining nipple.

19. The method of running subsurface well equipment in a well tubing through an enlarged curved tubing connected to the upper end of the well tubing, comprising, releasably connecting a first locomotive sized to be transported through the enlarged tubing to a second locomotive sized to be transported through the well tubing, pumping the first locomotive through the enlarged tubing carrying the second locomotive and well equipment therethrough, releasing the locomotives from each other, retaining the first locomotive adjacent the junction between the enlarged tubing and the well tubing, and pumping the second locomotive in the well tubing thereby carrying the well equipment to the desired location in the well tubing.

20. The method of claim 19 including retrieving well equipment from the well tubing after connecting the well equipment to the second locomotive comprising, pumping the second locomotive and the well equipment up the well tubing, connecting the second locomotive to the first locomotive, pumping the first locomotive up through the enlarged tubing carrying the second locomotive and the well equipment.