U.S. patent application number 11/231660 was filed with the patent office on 2007-03-22 for system, method, and apparatus for degassing tool for coal bed methane gas wells.
This patent application is currently assigned to Vetco Gray Inc.. Invention is credited to Kwong-Onn Chan, Henry He.
Application Number | 20070062693 11/231660 |
Document ID | / |
Family ID | 37882915 |
Filed Date | 2007-03-22 |
United States Patent
Application |
20070062693 |
Kind Code |
A1 |
Chan; Kwong-Onn ; et
al. |
March 22, 2007 |
System, method, and apparatus for degassing tool for coal bed
methane gas wells
Abstract
A coal bed methane degassing tool is installed at the bottom of
a first joint of production casing. As the casing is lowered into
the well hole, the tool is fished to the top of the casing as more
joints are added. The pressure at the tool may be recorded and
logged. Any excessive pressure observed at the tool may be bled off
by the tool automatically or manually. As more casing is tripped
in, the tool is brought to the top. At the end of the run a log of
formation pressure is established. Reservoir engineers can
determine reserves in coal bed methane wells drilled and completed
before the well is bled off and the tool is removed.
Inventors: |
Chan; Kwong-Onn; (Edmonton,
CA) ; He; Henry; (Edmonton, CA) |
Correspondence
Address: |
BRACEWELL & GIULIANI LLP
P.O. Box 61389
HOUSTON
TX
77208-1389
US
|
Assignee: |
Vetco Gray Inc.
|
Family ID: |
37882915 |
Appl. No.: |
11/231660 |
Filed: |
September 21, 2005 |
Current U.S.
Class: |
166/250.07 ;
166/250.04; 166/66 |
Current CPC
Class: |
E21B 43/006 20130101;
E21B 47/06 20130101 |
Class at
Publication: |
166/250.07 ;
166/250.04; 166/066 |
International
Class: |
E21B 47/00 20060101
E21B047/00 |
Claims
1. A downhole tool for installing a well, comprising: a body having
a plug shaft including a distal end, a fishing shaft located
opposite the distal end, and a bore extending from the distal end;
a plug mounted to the plug shaft and having an outer diameter
adapted to engage and seal the inner wall of production casing; and
a pressure gage in fluid communication with the bore and extending
from the fishing shaft, the pressure gage being adapted to measure
pressure in the well downwell from the downhole tool.
2. A downhole tool according to claim 1, wherein the plug shaft has
a diameter that is less than a diameter of the fishing shaft, a
shoulder is formed at an interface between the plug and fishing
shafts, and the plug abuts the shoulder.
3. A downhole tool according to claim 1, wherein the body has an
axis and the bore in the body extends along the axis from the
threaded end to the fishing shaft.
4. A downhole tool according to claim 1, wherein the plug is a
cementing plug.
5. A downhole tool according to claim 1, wherein the distal end of
the plug shaft is threaded, and a nut is fastened to the threaded
end of the plug shaft for securing the plug to the body such that
the plug is axially restrained by the nut.
6. A downhole tool according to claim 1, further comprising a
safety relief valve in fluid communication with the bore and
extending from the fishing shaft, the safety relief valve being
adapted to relieve excessive pressure in the well downwell from the
downhole tool.
7. A method of installing a well, comprising: (a) positioning a
downhole tool in a joint of production casing such that the
downhole tool seals against an inner surface of the joint of
production casing; (b) installing the joint of production casing in
the well; (c) fishing the downhole tool upward in a string of the
production casing; (d) reading the downhole tool for a gas
formation pressure of the well beneath the downhole tool; (e)
installing additional joints of production casing in the surface
casing to a desired depth of the well; and (f) reading the downhole
tool for the gas formation pressure of the well during step
(e).
8. A method according to claim 7, further comprising bleeding off
any excessive formation pressure through the downhole tool.
9. A method according to claim 8, wherein the excessive formation
pressure is a low pressure formation in excess of 50 psi.
10. A method according to claim 7, wherein the downhole tool is
positioned at lower ends of the joints of production casing.
11. A method of installing a well, comprising: (a) drilling a well
bore; (b) installing surface casing in the well bore to a nominal
depth; (c) positioning a downhole tool in an initial joint of
production casing such that the downhole tool seals against an
inner surface of the initial joint of production casing; (d)
installing the initial joint of production casing in the surface
casing; (e) fishing the downhole tool to an upper end of the
initial joint of production casing adjacent a surface of the well;
(f) reading the downhole tool at the surface of the well for a gas
formation pressure of the well beneath the downhole tool; (g)
installing additional joints of production casing in the surface
casing to a desired depth of the well; (h) reading the downhole
tool for the gas formation pressure of the well during step (g);
and (i) bleeding off any excessive formation pressure through the
downhole tool during steps (d) through (h).
12. A method according to claim 11, wherein step (c) comprises
positioning the downhole tool at a lower end of the initial joint
of production casing.
13. A method according to claim 11, wherein step (i) comprises low
pressure gas formation pressures on the order of 50 psi.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates in general to sensitive
formations containing low pressure gas, such as coal bed methane,
and, in particular, to an improved system, method, and apparatus
for a coal bed methane gas degassing tool.
[0003] 2. Description of the Related Art
[0004] Subterranean deposits of coal contain substantial quantities
of entrained methane gas. Limited production and use of methane gas
from coal deposits has occurred for many years. Coal seams may
extend over large areas of up to several thousand acres, and are
fairly shallow in depth, varying from a few inches to several
meters, singly or collectively in layers.
[0005] After the well is drilled, surface casing is typically
installed to a nominal depth. Production casing is then run inside
the surface casing to the desired depth of the well. The lowermost
joint of the production casing is sealed with a bridge plug as a
secondary seal against gas leaks. The primary means of handling the
gas during installation of the production casing is an inductor and
flare, which receives the gas via the annulus between the surface
and production casings. After the production casing is installed,
the bridge plug is drilled out to initiate production through the
production casing. Although this design is workable, an improved
design for sealing production casing during installation would be
desirable.
SUMMARY OF THE INVENTION
[0006] One embodiment of a system, method, and apparatus for a coal
bed methane degassing tool is installed at the bottom of a first
joint of production casing. As the casing is lowered into the well
hole, the tool is fished to the top of the casing as more joints
are added. The pressure at the tool may be recorded and logged. Any
excessive pressure observed at the tool may be bled off by the
tool. As more casing is tripped in, the tool is brought to the top.
Thus, at the end of the run, a log of formation pressure is
established. Reservoir engineers can determine reserves in coal bed
methane wells drilled and completed with a reverse circulation
center discharge (RCCD) process. The well is subsequently bled off
and the tool is removed.
[0007] The foregoing and other objects and advantages of the
present invention will be apparent to those skilled in the art, in
view of the following detailed description of the present
invention, taken in conjunction with the appended claims and the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] So that the manner in which the features and advantages of
the invention, as well as others which will become apparent are
attained and can be understood in more detail, more particular
description of the invention briefly summarized above may be had by
reference to the embodiment thereof which is illustrated in the
appended drawings, which drawings form a part of this
specification. It is to be noted, however, that the drawings
illustrate only an embodiment of the invention and therefore are
not to be considered limiting of its scope as the invention may
admit to other equally effective embodiments.
[0009] FIG. 1 is a sectional side view of one embodiment of a
downhole tool constructed in accordance with the present
invention;
[0010] FIG. 2 is a schematic view of a well utilizing the downhole
tool of FIG. 1; and
[0011] FIG. 3 is an enlarged schematic view of an upper portion of
the well of FIG. 2 shown utilizing the downhole tool of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0012] Referring to FIG. 1, one embodiment of a downhole or
degassing tool 11 is shown. The downhole tool 11 comprises a body
13 having an axis 15, a plug shaft 17 including, in one embodiment,
a threaded end 19. A fishing shaft 21 is located opposite the
threaded end 19, and a bore 23 extends along at least a portion of
the axis 15 from the threaded end 19. In the embodiment shown, the
plug shaft 17 has a diameter that is less than a diameter of the
fishing shaft 21.
[0013] A plug 25, such as a cementing plug or slips, is mounted to
the plug shaft 17. The plug 25 is a device that frictionally
maintains a position of the entire assembly within the production
casing. Other mechanical means for securing or locking the tool to
the casing also may be used. The plug 25 has an outer diameter 27
for engaging and sealing against the inner wall of production
casing, as will be described below. A nut 29 is fastened to the
threaded end 19 of the plug shaft 17 for securing the plug 25 to
the body 13. A shoulder 35 is formed at an interface between the
plug and fishing shafts 17, 21, and the plug 25 is axially
restrained between the shoulder 35 and the nut 29.
[0014] In one embodiment, the downhole tool 11 also comprises a
pressure gage 31 in fluid communication with the bore 23 and
extending from the fishing shaft 21. The pressure gage 31 measures
pressure in the well downwell from the downhole tool 11. The
downhole tool 11 also may comprise a safety relief valve 33 that is
also in fluid communication with the bore 23 and extending from the
fishing shaft 21. The safety relief valve 33 relieves excessive
pressure in the well downwell from the downhole tool 11.
[0015] Referring now to FIG. 2, one embodiment of a well system 41
for accessing a subterranean zone from the surface of the well. In
the embodiment described below, the subterranean zone is a coal
seam. It will be understood that other subterranean formations
and/or low pressure, ultra-low pressure, and low porosity
subterranean zones can be similarly accessed using the well system
of the present invention to remove and/or produce water,
hydrocarbons and other fluids in the zone, to treat minerals in the
zone prior to mining operations, or to inject or introduce fluids,
gases, or other substances into the zone.
[0016] The well system 41 includes an entry well bore 43, well 45,
one or more articulated well bores 47, a cavity 49, and a rat hole
51. Entry well bore 43 extends from the surface 53 towards the
subterranean zone 55. Well 45 extends from the terminus of entry
well bore 43 to the subterranean zone 55, although well 45 may
alternatively extend from any other suitable portion of entry well
bore 43. Where there are multiple subterranean zones 55 at varying
depths, as in the illustrated example, well 45 extends through the
subterranean zones 55 closest to the surface into and through the
deepest subterranean zone 55. Articulated well bores 47 may extend
from well 45 into each subterranean zone 55. Cavity 49 and rat hole
51 are located at the terminus of well 45.
[0017] Entry well bore 43 is illustrated as being substantially
vertical. However, it should be understood that entry well bore 43
may be formed at any suitable angle relative to the surface 53 to
accommodate, for example, surface 53 geometries and attitudes
and/or the geometric configuration or attitude of a subterranean
resource. Well 45 may be formed to angle away from entry well bore
43. It will be understood that well 45 may be formed at other
angles to accommodate surface topologies and other factors similar
to those affecting entry well bore 43. In addition, more than one
well 45 may be formed at different angular separations from entry
well bore 43.
[0018] As shown in FIG. 3, the present invention also comprises a
method of installing a well, such as a coal bed methane gas well.
The method comprises drilling a well bore; installing surface
casing 61 in the well bore to a nominal depth; positioning a
downhole tool 11 in an initial joint 63 of production casing such
that the downhole tool 11 seals against an inner surface of the
initial joint 63 of production casing. The downhole tool 11 may be
positioned at a lower end of the initial joint 63 of production
casing. During installation of the production casing, gas pressure
in the well may be handled via an inductor 64 or the like and
flared.
[0019] The method also comprises installing the initial joint of
production casing in the surface casing 61; fishing the downhole
tool with a fishing tool 65 to an upper end of the initial joint 63
of production casing adjacent a surface of the well; reading the
downhole tool 11 (e.g., pressure gage 31) at the surface of the
well for a gas formation pressure of the well beneath the downhole
tool 11; installing additional joints 67 of production casing in
the surface casing to a desired depth of the well; reading the
downhole tool 11 for the gas formation pressure of the well during
the previous step; and bleeding off any excessive formation
pressure (e.g., in excess of 50 psi) through the downhole tool 11
(e.g., safety relief valve 33) during preceding steps.
[0020] While the invention has been shown or described in only some
of its forms, it should be apparent to those skilled in the art
that it is not so limited, but is susceptible to various changes
without departing from the scope of the invention. For example, the
gas formation pressure at the downhole tool may be read remotely
(e.g., by wire, transmitted signal, etc.) to eliminate the need to
manually read the pressure gage at the surface of the well.
* * * * *