GB2112043A

GB2112043A - Methods and means for pulling sucker rod strings

Info

Publication number: GB2112043A
Application number: GB08222085A
Authority: GB
Inventors: Woodrow T Rutledge; Russel Paul Rutledge; John Edward Freeman
Original assignee: FIBERFLEX PROD Inc; FIBERFLEX PRODUCTS Inc
Current assignee: FIBERFLEX PROD Inc; FIBERFLEX PRODUCTS Inc
Priority date: 1981-08-27
Filing date: 1982-07-30
Publication date: 1983-07-13
Also published as: DK383382A; DE3231559A1; NL8202568A; SE8204880D0; NO822888L; SE8204880L; GB2112043B

Abstract

The present invention discloses a method and means for pulling a sucker rod string 40 from the tubing of a well bore. A separable connector 50 is provided between the sucker rod string 40 and a downhole pump 20. The separable connector 50 is designed to separate when a predetermined tension load greater than the operating load upon the sucker rod string is applied to it. If the downhole pump 20 is already stuck upon its seat or becomes stuck within the tubing while being withdrawn, tension on the sucker rod string is increased until the separable connector separates, and the sucker rod string may be withdrawn, leaving the pump within the tubing. <IMAGE>

Description

SPECIFICATION Methods and means for pulling sucker rod strings This invention relates to methods and means for pulling sucker rod strings and more particularly to a separable connector for use in a well bore in conjunction with a reciprocating pump in the lower portion of the well bore and a string of sucker rods used in actuating the pump from the surface.

Downhole reciprocating pumps have been used for years within tubing and casing to lift a column of fluid such as crude oil up the well bore to the surface of the earth. Such a pump is actuated by a string of sucker rods which connects the downhole pump to a reciprocating walking beam motor at the surface. The downhole pump is typically tubular in shape with an exterior diameter substantially the same as the interior diameter of the tubing. It is inserted into the tubing at the surface of the earth with the sucker rod string attached and lowered into the well bore until it seats upon an internal shoulder of the tubing provided for that purpose. In operation, the sucker rod string reciprocates a plunger within the pump.

The weight of the column of fluid above the pump keeps the-pump seated upon the shoulder. Since the area of the pump plunger is significantly less than the cross-sectional area of the pump, the upward lift required to raise the pump plunger is significantly less then the downward force of the fluid column acting on the entire pump, so that the pump is not unseated during normal operation.

On occasion the pump will stop operating for reasons such as a stuck plunger and require replacement. Ordinarily, the sucker rod string may be used to lift the pump up the inside of the tubing to the surface. On occasion, the pump becomes stuck on its seat within the tubing and cannot be dislodged. Alternatively, the pump may become stuck within the tubing while being withdrawn up the well bore. A stuck pump has required that the pump, the sucker rod and the tubing be pulled from the well bore. In the prior art a stuck pump has prevented the sucker rod string from being pulled separately from the tubing. Therefore the pump and the tubing had to be pulled with the sucker rod string still within the tubing.This is an extemely time consuming and expensive operation, since each individual length of tubing and each individual sucker rod must be broken out and each length of tubing must be lifted to clear the sucker rod still within it. The time and expense required to withdraw the tubing and the sucker rod string together far exceed the time and expense needed to first pull a sucker rod string and then pull a tubing string separately.

This invention attempts to provide methods and means for withdrawing a sucker rod string from a well bore.

This invention further attempts to provide methods and means for disconnecting a sucker rod string from a downhole reciprocating pump or similar tool in a well bore and withdrawing the sucker rod string from the well bore.

The present invention discloses a method and means for pulling a sucker rod string from the tubing of a well bore. A separable connector is provided between the sucker rod string and a downhole pump. This separable connector is designed to separate when a predetermined tension load greater than the operating load upon the sucker rod string is applied to it. If the downhole pump is either stuck upon its seat or becomes stuck within the tubing while being withdrawn, tension on the sucker rod string is increased until the separable connector separates, and the sucker rod string may be withdrawn, leaving the pump within the tubing.

Two types of separable connectors are disclosed. One has two threaded ends and a zone of reduced transverse cross-sectional area intermediate the two threaded ends. When the tension load applied to the connector is greater than the capacity of the zone, the zone fails and the connector separates.

The other type includes a male and a female section which, when engaged, have an aligned, transverse passage therethrough into which a shearable pin is fitted. This shearable pin provides the only means for transmitting a tension load from one section to the other section of the connector. When the tension load applied to the connector is greater than the shear capacity of the pin, the pin will shear and the connector will separate.

The disclosed methods include the provision of such a separable connector below the sucker rod string and above the downhole pump upon their insertion into the well. When it is desired to remove the pump, the operator supplies tension to the sucker rod string. If the pump is stuck or becomes stuck, the connector will separate, allowing the sucker rod string to be withdrawn.

The tubing string, together with the pump, may then be pulled from the well bore.

The present invention will be further described by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a vertical, partial sectional view having positioned therein a reciprocating pump and a sucker rod string including the separable connection of a first embodiment of the present invention; Fig. 2 is an enlarged side view of the female portion of the separable connection of a first embodiment of the present invention; Fig. 3 is an enlarged side view of the male portion of the separable connection of a first embodiment of the present invention; Fig. 4 is an enlarged partial sectional side view of the assembled separable connection of a first embodiment of the present invention; Fig. 5 is an enlarged sectional view of a second embodiment of the separable connection of the present invention; Fig. 6 is a side view of the separable member of Fig. 5; and Fig. 7 is a transverse cross-section of the separable member of Fig. 6 taken along section lines 7-7 of Fig. 6.

While the invention will be described in connection with the preferred embodiments and procedure, it will be understood that it is not intended to limit the invention to those embodiments or procedure. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within spirit and scope of the invention as defined by the appended claims.

Referring now to the drawings and first to Fig. 1, a well bore 10 is shown with casing 12 positioned therein and a production tubing section 1 4 inserted therein. The production tubing section 14 includes an internal shoulder 16, upon which is seated'an external shoulder 21 of a down hole pump 20. The pump 20 includes a barrel 22 enclosing a movable plunger 24. The plunger 24 is motivated by an attached plunger rod 26 having an upper connector 28. The connector 28 is threadably engaged to a separable connector 50 having upper end 52 and lower end 72. The upper end 52 of the separable connector 50 is theadedly engaged to a connector 42 of a sucker rod string 40. When the downhole pump 20 is in operation, the upper end of the sucker rod string 40 is connected to a reciprocating motor (not shown) at the surface 1 8 of the earth.

The details of the separable connector 50 are shown assembled in Fig. 4. Separable connector 50 includes upper female section 52 and lower male section 72 joined together by one or more shearable pins 94 and 96.

The female connector 52 is shown isolated in Fig. 2. It comprises a circular cylindrical body having a threaded end portion 54 at one end and a bore 58 at the other end 59. Bore 58 extends inwardly from end 59 to a face 60 and is surrounded by an annular wall 62. The annular wall 62 is penetrated by one or more oppositely opposed, coaxial pairs of holes, such as a pair 64 and a pair 66. The female section 52 may also be provided with one or more pairs of opposed flats 56 intermediate the two ends of the body for the application of a wrench used for the rapid connection of the connector 50 to a sucker rod (not shown) at the threaded end portion 54. The threads of end 54 may be threaded in accordance with the American Petroleum Institute standards.

The male section 72 is shown isolated in Fig. 3.

It comprises a circular cylindrical body having a threaded end member 74 at one end and a reduced diameter end portion 78 at the opposite end. The reduced diameter end portion 78 includes one or more transverse openings such as openings 84 and 86 preferably spaced at the same distance from end 79 of the portion 78 as holes 64 and 66 are from face 60. A groove 88 encircles the reduced diameter portion 78 at its junction with the central body of the male section 72. The male section 72 may also have one or more pair of opposed flats 76 intermediate its ends for the application of a wrench used in the rapid connection of the threaded end portion 74 to, preferably, the down hole reciprocating pump 20.

Referring to Fig. 4, the exterior diameter of the reduced diameter portion 78 of the male section 72 is substantially equal to the interior diameter of the central bore 58 of the female section 52.

When the male section 72 is inserted into the female section 52, the pairs of holes 64 and 66 of the female section 52 align themselves with the transverse openings 84 and 86 of the male section 72. Shearable pins 94 and 96 are press fitted into the passageways formed by the aligned openings 64 and 84 and the aligned openings 66 and 86 respectively. A resilient O-ring 92 placed in the circular groove 88 seals the assembled separable connector 50.

The shearable pins 94 and 96 are manufactured so that the separable connector 50 will separate by shearing the shearable pins 94 and 96 when a tension load greater than a predetermined load is applied. The predetermined load can be controlled by varying the diameters of the transverse openings 64 and 84 and 66 and 86, and, thereby, that of the shearable pins 94 and 96 and by modifying the composition of the shearable pins 94 and 96. It is desirable that the shearing load be substantially greater than the tension force required for normal operation of the downhole reciprocating pump 20. Thus the separable connector 50 will remain assembled upon any upward movement of the pump plunger 24 during normal operation.

A second embodiment 1 50 of the separable connector is shown in Fig. 5. It has a separable member 1 60 and two internally threaded couplings 170 and 172. As seen in Figs. 6 and 7, the separable member 1 60 has two opposed, externally threaded ends 1 62 and 1 64 connected by a zone of reduced transverse cross-sectional area 166. The separable member 160 is preferably machined from one piece of stock with the transverse cross-sectional area of the zone 1 66 sized so that the separable member 1 60 will fail at a predetermined load.The zone 1 66 is preferably round and solid as shown in Fig. 7, but is may be of any shape or even have longitudinal passages therethrough, as a tube, so long as the transverse cross-sectional area remains that required for failure at the desired predetermined load.

The separable member 1 60 is preferably used with the two internally threaded couplings 1 70 and 172, which may be standard sucker rod connectors. The separable member 1 60 and the two couplings 170 and 1 72 may be made up and torqued down with band type friction wrenches. A thread sealer may be applied to the threads of the separable member 1 60 or the two couplings 1 70 and 172 before making them up to ensure that they do not become unscrewed while in service. The separable connector 1 50 is connected between the sucker rod string 40 and the downhole pump 20 by threaded engagement of those parts with the internal threads of the connectors 170 and 172.

When the predetermined load of the separable connector 1 50 is exceeded, the zone 1 66 of the separable member 1 60 first elongates and then fails, thereby separating the separable connector 1 50. This separable connector 1 50 is inserted below the sucker rod string 40 and above the pump 20 just as the separable connector 50 is.

In operation, the separable connector 50 or 1 50 of the present invention is connected between the plunger rod 26 of the downhole pump 20 and the sucker rod string 40 at the time the pump 20 and string 40 are inserted into the well bore 10, as shown in Fig. 1. Subsequently, when it is desired to remove the downhole reciprocating pump 20 from the well bore 10, because of a malfunction or any other reason, the sucker rod string 40 is disconnected from the reciprocating motor and is connected instead to a connector 38 acting through a wire line 34 over a sheave 36 to a tension means 30, commonly truck mounted. The wireline is used to lift the sucker rod string 40 which lifts the pump 20 from internal shoulder 16 and raises it up inside the tubing 14 to the surface 18 of the earth, where the pump 20 may be withdrawn from the well bore 10.

If the pump 20 is stuck on its shoulder 16 and connot be dislodged or if the pump 20 becomes stuck in the tubing 14 while being lifted upward, the previously installed separable connector 50 or 1 50 is caused to separate. Separation is brought about by sufficient tension applied by the tension means 30 to exceed the predetermined tension load. The separable connector 50 or 1 50 then parts, freeing the sucker rod string 40 from the stuck pump 20. The sucker rod string 40 may then be withdrawn from the tubing 14 in a known manner. Finally, the tubing 14 containing the stuck pump 20 is withdrawn from the well bore 10, or a fishing tool adapted to connect to the remaining portion of the connector 50 or 1 50 may be used when necessary.

Thus it is apparent that there has been provided, in accordance with the invention, a method and means for pulling a sucker rod string that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.

Claims

1. A separable connector for use with a sucker rod string and a down hole reciprocating pump within a tubing string of a well, comprising: (a) two end members including first means for connection to the string and the pump, and (b) a center member, said members and said center member including correlative second means for connection of said center member to said end members and said centre member further including a portion having a transverse crosssectional area sized to separate said portion upon application of a predetermined tension force to said connector.

2. The connector of claim 1 wherein said correlative second means of said center member includes two end sections, each of said end sections having thread means for threadably connecting to one of said correlative second means of said end members.

3. The connector of claim 1 or Claim 2 wherein said center member is intermediate said end members and said end members surround said center member.

4. The connector of any one of claims 1 to 3, wherein said center member includes a portion having a transverse cross-sectional area sized to separate said portion upon application of a predetermined tension force to said connector, which force is substantially greater than the tension force applied during normal operation of the pump.

5. A separable connector for use with a sucker rod string and a down hole reciprocating pump within a tubing string of a well, comprising: (a) a male section and a female section, said sections mounted in close fitting relationship with each other, each of said sections having portions defining at least one opening therein, said opening being in a correlative, juxtaposed relationship when said sections are in said close fitting relationship; and (b) shear means positioned within said portions defining the openings to connect the male and female sections, said shear means being sized to shear upon the application of a predetermined tension force to said connector.

6. The connector of claim 5, wherein said shear means is sized to shear upon the application of a predetermined tension force to said connector, which force is substantially greater than the tension force applied during normal operation of the pump.

7. The connector of claim 5 or claim 6 wherein said male and female sections include a box and a pin, said box and pin having means for connection to each other by said shear means.

8. A separable connector for use with a sucker rod string and a downhole pump of a well, comprising: (a) end means for connection to the string and the pump, and (b) a center section connected to said end means, said section having a transverse crosssectional area sized to separate into two parts upon application of a predetermined tension force to said connector.

9. An assembly for use with a well having a tubing string adapted to receive a downhole pump, comprising: (a) a sucker rod string within the tubing string; (b) a separable connector including two end members having first means for connection to said string and the pump, and including a center member having: (i) end portions, each of said end portions having second means for connection to one of said end members, and (ii) a center portion having a transverse crosssectional area sized to separate upon application of a predetermined tension force to said connector, which force is substantially greater than the tension force applied during normal operation of the pump.

1 0. A mechanism for enabling a sucker rod string to be pulled from a downhole pump mounted in a tubing string of a well, comprising a separable connector, said separable connector including: (a) connection means for connection to the sucker rod string and to the pump for enabling the pumping of fluids from the well responsive to reciprocating movement of the sucker rod string within the tubing string from a first force applied to the sucker rod string; and (b) separating means responsive to the tensioning of the sucker rod string to a predetermined second force, which second force is significantly greater than the first force, for separating said separable connector into two disconnected portions, one portion attached to the string and one portion attached to the pump, whereby the string is disconnected from the pump and the sucker rod string can be pulled from the well and the pump can be left in the well.

11. The mechanism of claim 10, wherein said separable connector includes two threaded ends and a center member intermediate said two threaded ends and connected thereto, and wherein said threaded ends are connected only by said center member.

12. The mechanism of claim 10, wherein said separable connector includes two threaded ends and shear means, said ends having means for receiving and being connected by said shear means, and wherein said threaded ends are connected by said shear means.

13. A method of enabling a sucker rod string connected to a downhoie pump to be pulled by tension force from a tubing string of a well, wherein the pump operates by tension force, string of a well, wherein the pump operates by tension force, comprising the steps of: (a) assembling a tension responsive separable connector between the sucker rod string and the downhole pump; (b) installing the assembly in the well; (c) applying a separating tension force to the sucker rod string, said separating tension force being significantly greater than the operating tension force said, separating tension force being sufficient to cause separation of the separable connector, whereby the sucker rod string is disconnected from the downhole reciprocating pump; and (d) pulling the sucker rod string from with-in the tubing string without the downhole reciprocating pump being attached thereto.

14. A method as claimed in claim 13, wherein step (a) includes assembling a separable connector having two threaded ends joined by a center portion of reduced transverse crosssectional area to the sucker rod string and pump with one threaded end connected to the pump and one threaded end connected to the sucker rod string, and wherein step (c) includes separating the center portion by applying the separating tension force.

1 5. A method as claimed in claim 13, wherein step (a) includes assembling a separable connector having two threaded ends joined by shearable means to the sucker rod string and the pump with one threaded end connected to the pump and one threaded end connected to the sucker rod string, and wherein step (c) includes separating the connector by shearing the shearable means by applying the separating tension force.

1 6. A separable connector as claimed in claim 1, substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.

1 7. A method as claimed in claim 13, substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.