Wells – Processes – Parallel string or multiple completion well
Patent
1998-09-23
2000-02-29
Schoeppel, Roger
Wells
Processes
Parallel string or multiple completion well
1661176, 166384, E21B 708
Patent
active
060297476
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to through-tubing lateral re-entry, by which is meant the ability to enter an existing lateral offshoot from a main borehole without removal of downstream completion tubing from the main borehole.
The need for such an ability has arisen because of the increasingly common practice of improving well output by drilling a lateral bore, or more often multiple lateral bores, from a common main borehole in order to gain access to different levels or zones of an oil or gas reservoir.
Typically, the main borehole, at least in the region of the multi-lateral offshoots, can be deviated from the vertical plane or even horizontal, and the multi-lateral offshoots can themselves be deviated from the vertical plane or even horizontal.
This means that the well needs to be serviced by coiled tube technology relying on hydraulics, rather than by traditional wireline technology relying on gravity.
It is known for a lateral bore to be drilled by providing a steel liner for the main borehole with a window which is closed by a softer material such as fibreglass. The liner is also provided upstream of the window with a latch down collar having an orienting device. Using conventional drilling technology, the steel liner is lowered into position and then fixed in position by cement, with the window facing in a predetermined direction.
A whipstock is run down through the liner until an orienting device on the whipstock locates with the orienting device on the liner to latch and hold the whipstock at a desired orientation.
Next, a drill string is run down through the liner and is deflected by the whipstock to drill through the softer material closing the window before drilling into the surrounding stratum. After the lateral bore has been drilled, the drill string is withdrawn and then the whipstock is retrieved leaving the latch down collar with its orienting device. Finally, conventional completion tubing is run down through the main borehole to a desired position downstream of the lateral bore.
There are a number of reasons why it would be desirable to be able to re-enter a selected lateral bore after it has been drilled.
For example, there may be a wish for a particular lateral bore to be: or the surrounding stratum; presence or absence of oil or water; or sleeve, at an interface of the lateral bore and the surrounding stratum.
There are also, however, a number of reasons why it would not be desirable to remove the downstream completion tubing--not only does the downstream completion tubing protect the main borehole casing from corrosive well fluids and provide total control over the well fluids, but removal in a so-called workover can cost up to $1,000,000.
It has recently been proposed that a special small diameter whipstock be deployed through the completion tubing and then oriented directly in the large diameter liner to allow through-tubing lateral re-entry.
According to one aspect of the present invention, however, a method is provided for allowing entry of an existing lateral offshoot from a main borehole, without removal of downstream completion tubing from the main borehole, comprising the use of both a liner and a whipstock inserted through the completion tubing to a position within the liner, characterised in that an intermediate device has been provided which, in use, is located between the liner and the whipstock so that the whipstock merely needs to locate with the intermediate device rather than the liner.
Other aspects of the present invention reside in the provision of an intermediate device for use in the method and of a well assembly resulting from use of the method.
Such an intermediate device needs to be located in the liner before the completion tubing is located in the liner, and a separate intermediate device needs to be associated with each of the lateral bores for which re-entry is to be required.
Nevertheless, an advantage of the present invention is that the whipstock can be of a simple construction, because it merely needs to locate with the intermediate device, whose inne
REFERENCES:
patent: 2797893 (1957-07-01), McCune et al.
patent: 5195591 (1993-03-01), Blount et al.
patent: 5222554 (1993-06-01), Blount et al.
patent: 5311936 (1994-05-01), McNair et al.
Morrell Terence Robert
Norris Robert Martin
Schoeppel Roger
Tuboscope I/P Inc.
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