Well Tubing Tie Back Method And Apparatus

Abstract

A tool adapted for insertion in a tubing string in oil and gas wells is sized for fitting over and sealingly connecting the tool to a parted tubing string already in the well whereby leak-proof fluid communication can be established in the reconstructed tubing string. Especially designed for reestablishing communication with tubing that has been parted, for example as with a mechanical or chemical tubing cutter, the lower inner section of the tool has a plurality of spaced rubber O-rings to provide a first sealing action and a reduced internal diameter above the O-rings for establishing a beveled metal-to-metal seal with the previously parted tubing. The upper section of the tool is threaded for connection to the upper string of tubing while the lower end of the tool has a cut lip guide for scooping the parted tubing end into the receptacle lower section of the tool containing the sealing members. In an alternative embodiment, an additional resilient seal aids in providing an additional sealing effect for the beveled metal-to-metal seal.

Description

BACKGROUND OF THE INVENTION

The present invention relates, generally, to methods and apparatus for improving the efficiency of production from oil and gas wells, and in particular, to methods and apparatus for reestablishing communication with one or more tubing strings having been previously parted.

In the art of oil and gas production, for various reasons, tubing necessarily is parted, as for example, by well-known mechanical or chemical cutters. Tubing is often stuck near the bottom of the well and needs to be changed out above the retained point. Again, a packer or sand screen can sometimes not be retrieved and it is necessary to separate the tubing at some point above the sand screen or packer.

It is therefore the primary object of this invention to provide a new and improved method and apparatus for reestablishing a substantially leak-proof fluid communication between a string of tubing and a previously parted tubing string;

It is a further object of the invention to provide a new and improved tool of such dimensions as to allow a fluid communication path, between strings of tubing as to cause no reduction in flow volume;

It is still another object of the invention to provide a tool for insertion between strings of tubing having internal dimensions such that an artificial lift can be installed without normal removal of all previous down hole installation equipment; and

It is yet another object of the invention to provide a tool for insertion between strings of tubing of such dimensions that such tools can be used with multiple tubing strings, even in connecting two parted dual tubing strings at the same point in the casing.

The objects of the invention are achieved, broadly, by the provision of an apparatus, and method for using such apparatus, which is threadedly attachable at one end to a tubing string and which at its other end is sealably attachable to a previously parted tubing string within the borehole to accomplish fluid communication between the two strings of tubing.

These and other objects, features and advantages of the present invention will be readily apparent to those skilled in the art from a reading of the following detailed specification and drawing, in which:

FIG. 1 is a side elevational view of an apparatus according to the invention;

FIG. 2 is a side elevational view of an alternative embodiment according to the invention; and

FIG. 3 is a side elevational view of a section of parted tubing finding special utility with the apparatus and method according to the invention, the parted tubing being one of a dual string of tubing located in a side elevational view of a borehole leading from the earth's surface.

Referring now to the invention in more detail, especially to FIG. 1, there is illustrated a tool 10 adapted to be threadedly attached to a tubing string (not illustrated) at the upper end 11 of tool 10. Depending upon the need, the threaded section 11 could have male or female threads for attachment to the tubing string which would normally extend to the earth's surface (also not illustrated but for all practical purposes would resemble the unparted tubing string illustrated in FIG. 3.) For ease of fabrication, the tool 10 is formed of two sections 12 and 13, the upper section 12 having a cylindrical internal diameter from points 14 to 15 of 2 inches to accommodate a full volume flow with standard 23/8 inches O.D. tubing which might be used in a 7 inch cased bore hole. This also allows instrumentation or valves to be lowered through the tool 10 which can normally be lowered through the remainder of the tubing string. The upper section 12, in addition to having its upper end 11 threaded for connection to the tubing string, is also threadedly attached to the lower section 13 of the tool 10, the threads therebetween generally identified by the numeral 16. The length of the threads 16 is nominally set at about 21/4 inches, being the dimension between points 17 and 18. The upper section 12, being dimensioned between points 19 and 20, is nominally 8 inches.

The lower end of the upper section 12 is flaired out or tapered at points 21 to mate with the internal dimension of the lower section 13 of the tool 10, that internal dimension being approximately 2.425" .+-. 0.010" as measured between points 22 and 23.

Within and around the cylindrical inner surface of the lower section 13 are a plurality of spaced grooves 24, for example nine, each of which is sized to snugly receive a resilient O-ring 25, for example of rubber, each O-ring 25 having a thickness of 0.125 inches. The O-rings 25 are dimensioned to have an internal diameter, as illustrated between points 26 and 27 of about 2.375 inches. Thus, a parted tubing having a 2.375 O.D. will form a seal with the internal surface of the O-rings 25.

At the lower end of the lower section 13 is a cut-away scooping section 28 having an approximate 45.degree. angle cut therein which serves to cut through any sand or debris in passing through the bore hole and which also serves to "scoop" the parted tubing into the lower end of the tool 10.

FIG. 2 illustrates an alternative embodiment of the invention wherein an additional resilient seal 30 is formed adjacent the tapered shoulder 21 whereby the metal-to-metal seal effect discussed with respect to the embodiment of FIG. 1 is enhanced. By way of example, the seal 30 could also be rubber.

Referring now to FIG. 3, there is illustrated an earth bore hole 40 having a casing 41. A conventional dual string packer 42 is shown set within the bore hole having a pair of tubing strings 43 and 44 passing therethrough, all of which is conventional in the art. During normal operation, each of the tubing strings 43 and 44 would reach the earth's surface 45. However, as shown in FIG. 3, the tubing 43 has been parted at the point 46, as for example, by a mechanical or chemical tubing cutter. As is often the case, the point 46 on the tubing has a jagged edge.

In the operation of the apparatus according to the present invention, the tool 10 is threaded into the end of a string of tubing and the tool 10, and its new string of tubing, is lowered into the bore hole 40. By scooping around with the bottom of the tool 10, the parted tubing 43 is scooped into the tool 10. The new tubing string and tool is further lowered, past the O-rings 25, up to the tapered shoulder 21. The further application of tubing weight forces the parted tubing end to conform to the tapered shoulder 21 to effect an adequate seal for subsequent production.

As illustrated in FIG. 2, if the resilient seal 30 is added to the tapered shoulder 21, additional sealing is effected.

Thus there has been illustrated and described herein an economical method and apparatus for connecting and sealing a parted tubing string. It should be appreciated that although the specific embodiment illustrates the connection of tubing in a multiple string environment, the same apparatus can be used in single string environments. It should also be appreciated that the tool 10 is dimensioned such that two such reconnections in the dual string situation can be accomplished at the same point in the casing. It should also be appreciated that testing of the apparatus according to the invention has proved to be quite successful even though the previously parted tubing does not butt up completely against the tapered shoulder, relying solely upon the O-ring seal.

Claims

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

1. An apparatus for establishing fluid communication between a string of tubing and a parted string of tubing in an earth bore hole, comprising:

a tool body having an upper threaded end for threadedly engaging a string of tubing, said tool body having a first upper cylindrical bore of one dimension at least as large as the internal diameter of said parted string of tubing and a second lower cylindrical bore of a larger dimension at least as large as the external diameter of said parted string of tubing; and

a shoulder having a resilient member attached thereto interfacing said upper and lower bores, said shoulder being downwardly and radially outwardly tapered from said upper bore to said lower bore, whereby said tool body can be extended over said parted string of tubing and additional tubing weight applied until said parted string of tubing contacts said resilient member to the extent necessary to form a seal between said tapered shoulder and the top of said parted string of tubing.

2. The method of establishing a fluid communication path between a first string of tubing and a parted string of tubing in an earth bore hole comprising the steps of placing a tool body on the lower end of said first string of tubing wherein said tool body has at least one sealing element internal thereto, running said first string of tubing and said attached tool body down in the earth bore hole until said tool body extends over said parted string of tubing to engage said at least one sealing element with said parted string of tubing, and then deforming the uppermost portion of the parted string of tubing by applying additional weight of the first string of tubing to said uppermost portion of said parted string of tubing to thereby provide additional sealing between said first string and said parted string of tubing.

3. The method of establishing a fluid communication path between a first string of tubing and a parted string of tubing in an earth bore hole comprising the steps of placing a tool body on the lower end of said first string of tubing, running said first string of tubing and said attached tool body down in the earth bore hole until said tool body extends over said parted string of tubing, and then deforming the uppermost portion of the parted string of tubing by applying additional weight of the first string of tubing to said uppermost portion of said parted string of tubing to thereby provide a fluid seal between said first string and said parted string of tubing.