Wells – Processes – Parallel string or multiple completion well
Reexamination Certificate
2000-01-24
2001-05-15
Suchfield, George (Department: 3672)
Wells
Processes
Parallel string or multiple completion well
C166S117500, C166S237000, C166S242600, C166S382000
Reexamination Certificate
active
06230806
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to the drilling and completion of subterranean wells, and, more particularly, but not by way of limitation, to improved apparatus and methods for precisely locating tools relative to a predetermined target depth in such wells. Still more particularly, but not by way of limitation, the present invention pertains to improved apparatus and methods for precisely locating tools relative to a predetermined target depth in offshore, multilateral wells drilled from a floating drilling rig.
HISTORY OF THE RELATED ART
Before running certain critical downhole processes during the drilling or completion of a subterranean well, one must first determine the target depth for the process. Once this target depth is determined, a downhole tool is typically run into the well and located at the target depth within a specific tolerance. When drilling on-shore wells or when drilling from a fixed platform offshore, conventional tools such as a gamma ray survey tool or a collar log are typically utilized in order to position a downhole tool relative to the predetermined target depth. When the gamma ray survey tool indicates that the downhole tool is at the proper depth, the tool is typically fixed at this depth using a conventional anchoring system, such as a packer.
FIG. 1
illustrates a conventional floating drilling rig or “floater”
10
. Floater
10
generally comprises a drilling rig
12
, a semi-submersible
14
, and a casing
16
. Semi-submersible
14
floats on, and supports drilling rig
12
proximate to, the surface of ocean
18
. Although not shown in
FIG. 1
, semi-submersible
14
is anchored to a surface
20
of ocean floor
22
by conventional anchoring means. Casing
16
extends from drilling rig
12
, through ocean
18
, and into ocean floor
22
. A predetermined target depth
24
within ocean floor
22
has been determined for a downhole process.
When drilling offshore from conventional floater
10
, it is extremely difficult, and sometimes impossible, for conventional equipment such as a gamma ray survey tool to accurately indicate the depth of a downhole tool relative to target depth
24
. This problem occurs because, in contrast to on-shore drilling or offshore drilling from a fixed platform, waves on the surface of ocean
18
continually move semi-submersible
14
, and a work string supporting a downhole tool within casing
16
, in a vertical direction.
One conventional technique used to address this problem is illustrated in FIG.
2
. As shown in
FIG. 2
, casing
16
has been installed in a wellbore
26
within ocean floor
22
. Casing
16
has been formed with a no-go shoulder
30
. In addition, a work string
28
has been formed with a fixed no-go sleeve
32
. A downhole tool
34
and a conventional mechanically or hydraulically actuated anchoring system
36
, such as a packer, have been coupled to work string
28
below fixed no-go sleeve
32
.
Work string
28
is run into casing
16
until fixed no-go sleeve
32
rests on no-go shoulder
30
. If anchoring system
36
is solely hydraulically set, downhole tool
34
is located at target depth
24
when fixed no-go sleeve
32
is resting on no-go shoulder
30
.
With a hydraulically actuated anchoring system
36
, work string
28
is pressured up to set anchoring system
36
. However, this hydraulic pressure often causes a “ballooning effect” in work string
28
, resulting in work string
28
stretching several inches below no-go shoulder
30
. Such stretching moves downhole tool
34
several inches from its desired target depth
24
, potentially endangering the success of the downhole process to be performed by downhole tool
34
. This ballooning effect may also place portions of work string
28
in residual tension or compression. When work string
28
is pressured down after anchoring system
36
is set, this residual tension and compression is transferred to, and may damage, downhole tool
34
.
To set a mechanically actuated anchoring system
36
, work string
28
is first lifted above no-go shoulder
30
, as indicated by position
38
of fixed no-go sleeve
32
shown in dashed lines in FIG.
2
. This lifting attempts to locate downhole tool
34
exactly at target depth
24
. Some work string weight is then used to set anchoring system
36
, such as, by way of example, releasing tension in the conventional rig hoist system on semi-submersible
14
supporting work string
28
. As will be appreciated by one skilled in the art, such lifting of no-go sleeve
32
is necessary so that the setting force is transmitted to anchoring system
36
instead of no-go shoulder
30
. However, due to inaccuracies involved in such lifting, downhole tool
34
may not be positioned exactly at target depth
24
. This potential problem endangers the success of the downhole process to be performed by downhole tool
34
.
Of course, with an anchoring system
36
that is initially hydraulically and then fully mechanically set, all of the above-described problems may occur.
Therefore, a need exists in the petroleum industry for improved apparatus and methods for precisely locating downhole tools relative to a predetermined target depth in offshore wells drilled from a floating drilling rig. One specific application that requires repeated, precision locating of a downhole tool relative to a predetermined target depth, and thus is particularly susceptible to the above-described problems, is the drilling and completion of offshore, multilateral wells drilled from floating drilling rigs. As used in this document, a multilateral well is a well having a substantially vertical main wellbore that contains multiple wellbores extending generally laterally from the main wellbore. Multilateral wells allow an increase in the amount and rate of production by increasing the surface area of the wellbores in contact with the reservoir, or reservoirs. Thus, multilateral wells are becoming increasingly important, both from the standpoint of new drilling operations and from the reworking of existing wellbores, including remedial and stimulation work.
The problem of lateral wellbore (and particularly multilateral wellbore) completion has been recognized for many years, as reflected in the patent literature. For example, U.S. Pat. No. 4,807,704 discloses a system for completing multiple lateral wellbores using a dual packer and a deflective guide member. U.S. Pat. No. 2,797,893 discloses a method for completing lateral wells using a flexible liner and deflecting tool. U.S. Pat. No. 2,397,070 similarly describes lateral wellbore completion using flexible casing together with a closure shield for closing off the lateral. In U.S. Pat. No. 2,858,107, a removable whipstock assembly provides a means for locating (e.g. accessing) a lateral subsequent to completion thereof. U.S. Pat. Nos. 4,396,075; 4,415,205; 4,444,276; and 4,573,541 all relate generally to methods and devices for multilateral completions using a template or tube guide head. Other patents of general interest in the field of horizontal well completion include U.S. Pat. Nos. 2,452,920 and 4,402,551.
More recently, U.S. Pat. Nos. 5,318,122; 5,353,876; 5,388,648; and 5,520,252 have disclosed methods and apparatus for sealing the juncture between a vertical well and one or more horizontal wells. In addition, U.S. Pat. No. 5,564,503, which is commonly assigned with the present invention and is incorporated herein by reference, discloses several methods and systems for drilling and completing multilateral wells. Furthermore, U.S. Pat. Nos. 5,566,763 and 5,613,559, which are commonly assigned with the present invention and are incorporated herein by reference, both disclose decentralizing, centralizing, locating, and orienting apparatus and methods for multilateral well drilling and completion.
Notwithstanding the above-described efforts toward obtaining cost-effective and workable multilateral well drilling and completions, a need still exists for improved apparatus and methods for precisely locating tools relative to a predetermined target depth in offshore, multi
Halliburton Energy Service,s Inc.
Imwalle William M.
Smith Marlin R.
Suchfield George
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