Dual Bore Packer with Axially Offset Mandrel Threads

Abstract

A dual bore packer features axially offset tapered thread connections so that the pressure rating and size of the connections in each of the bores can be as large as possible. This is enabled by providing as thick a wall as possible between the bores in the zone where the connecting tapered thread is placed.

Description

FIELD OF THE INVENTION

The field of the invention is dual bore packers and more particularly packers where the mandrel end connections are axially offset to allow greater wall area about the thread for the required pressure rating.

BACKGROUND OF THE INVENTION

Typically dual bore packers have two adjacent bores with threaded end connections for connecting a tubular string or a cable. One application for dual bore packers is for electric submersible pump service where the smaller of the bores is for a power cable to the pump and the larger bore is connected to the discharge of the pump to bring produced fluids to the surface. Some examples of dual bore packers with axially aligned threads are U.S. Pat. No. 9,611,722 and U.S. Pat. No. 6,390,198.

Typically the threaded connections have to deliver a required pressure rating and if the threads are disposed next to each other at the upper face of the mandrel there has to be a tradeoff between making the thread as large as possible for less resistance to flow and making the connections stout enough to handle the anticipated operating pressures for the application. Since the thread forms are tapered juxtaposing two threads near each other limits the available wall between them so as to reduce the pressure rating of the connections. In dual bore packers the center of each bore is offset from the center of the packer.

The present invention offers a simple solution to this design conflict between making the bores as large as possible and giving the connections the highest possible pressure rating. The solution is to axially offset the threads in adjacent bores to maximize the available surrounding wall thickness so that in a given packer mandrel size the diameter and pressure rating of the two bores is maximized. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention can be determined from the appended claims.

SUMMARY OF THE INVENTION

A dual bore packer features axially offset tapered thread connections so that the pressure rating and size of the connections in each of the bores can be as large as possible. This is enabled by providing as thick a wall as possible between the bores in the zone where the connecting tapered thread is placed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view of a dual bore packer showing the offset thread locations in adjacent bores;

FIG. 2 is an end view of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A mandrel end 10 of a dual bore packer of a type known in the art is shown in FIG. 1. First bore 12 is disposed parallel to second bore 14. In one application bore 12 is larger than bore 14 such as in applications for an electric submersible pump where the production discharge line from the pump is connected to bore 12 and a power cable goes through bore 14. Typically the bores 12 and 14 have their centers offset from the center of the mandrel 10. Bore 12 has a threaded connection 16 axially offset and preferably not overlapping from thread 18 in bore 14. In the case of more bores than two it is preferred that each connection be at least offset if not non-overlapping from all the other connections on the mandrel. Because thread 18 is tapered, the result is the wall 20 between the bores 12 and 14 gets thinner. The same is true for thread 16 at wall portion 22. However, because threads 16 and 18 are axially offset and preferably non-overlapping in the axial direction there is no need to reduce the pressure rating of either threaded connection because placement of the thread takes away some of the wall. Instead the available wall thickness at each thread location is as large as possible availing a higher pressure rating to the connection than if the two threads were axially aligned or even if they were only in part axially overlapping. While tapered threads are discussed as the end connections, those skilled in the art will appreciate that other types of connections are envisioned whether threaded, socket welded, bayonet or another form of connection.

The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:

Claims

1. A connection arrangement for a multi-bore packer for borehole use, comprising: a mandrel having multiple bores coextensive from a common top to a common bottom end of said mandrel, each said bore having a connection within said mandrel wherein said connections within said bores are axially offset from each other.

2. The connection arrangement of claim 1, wherein: said connections do not axially overlap.

3. The connection arrangement of claim 2, wherein: said connections comprise tapered thread.

4. The connection arrangement of claim 2, wherein: at least one said connection starts at an end of said mandrel.

5. The connection arrangement of claim 2, wherein: said bores are different sizes.

6. The connection arrangement of claim 2, wherein: said bores have centers offset from a center of said mandrel.

7. The connection arrangement of claim 2, further comprising: a power cable for an electric submersible pump connected to one of said bores and a tubular string connected to another of said bores to direct flow from said pump to a remote location.

8. The connection arrangement of claim 1, wherein: said mandrel comprises two said bores.