U.S. patent application number 10/227057 was filed with the patent office on 2004-02-26 for system and method for subterranean access.
Invention is credited to Zupanick, Joseph A..
Application Number | 20040035582 10/227057 |
Document ID | / |
Family ID | 31887386 |
Filed Date | 2004-02-26 |
United States Patent
Application |
20040035582 |
Kind Code |
A1 |
Zupanick, Joseph A. |
February 26, 2004 |
System and method for subterranean access
Abstract
A system for accessing a subterranean zone from the surface
includes a first, second and third entry well bore extending from
the surface, the first, second and third entry well bores located
on the same drilling pad at the surface. A slanted well bore
extends from each of the entry well bores to the subterranean zone.
A substantially horizontal drainage pattern extends from the
slanted well bores into the subterranean zone.
Inventors: |
Zupanick, Joseph A.;
(Pineville, WV) |
Correspondence
Address: |
BAKER BOTTS L.L.P.
2001 ROSS AVENUE
SUITE 600
DALLAS
TX
75201-2980
US
|
Family ID: |
31887386 |
Appl. No.: |
10/227057 |
Filed: |
August 22, 2002 |
Current U.S.
Class: |
166/313 ;
166/50 |
Current CPC
Class: |
E21B 43/006 20130101;
E21B 43/305 20130101; E21B 43/14 20130101 |
Class at
Publication: |
166/313 ;
166/50 |
International
Class: |
E21B 043/12 |
Claims
What is claimed is:
1. A method for accessing a subterranean zone from the surface,
comprising: forming a first entry well bore from the surface;
forming one or more slanted well bores from the first entry well
bore to the subterranean zone; forming a second entry well bore
from the surface, the second entry well bore located on the same
drilling pad as the first entry well bore at the surface; forming
one or more slanted well bores from the second entry well bore to
the subterranean zone; forming a third entry well bore from the
surface, the third entry well bore located on the same drilling pad
as the first and second entry well bores at the surface; forming
one or more slanted well bores from the third entry well bore to
the subterranean zone; and forming a substantially horizontal
drainage pattern from each of the slanted well bores into the
subterranean zone.
2. The method of claim 1, wherein the horizontal drainage patterns
comprise a horizontal well bore extending from the slanted well
bore and a plurality of lateral well bores extending from the
horizontal well bore.
3. The method of claim 2, wherein the horizontal drainage patterns
comprise a crow's foot configuration.
4. The method of claim 2, wherein the lateral well bores are
configured to drain an area of the subterranean zone of at least
640 acres.
5. The method of claim 2, wherein the horizontal drainage patterns
comprise a pinnate configuration.
6. The method of claim 1, further comprising removing resources
from the subterranean zone through the horizontal drainage patterns
to the surface.
7. The method of claim 1, further comprising forming an enlarged
cavity in each of the slanted well bores proximate to and above the
subterranean zone.
8. The method of claim 1, further comprising forming an enlarged
cavity in each of the slanted well bores above the horizontal
drainage pattern.
9. The method of claim 7, wherein the enlarged cavity is located
proximate to the junction of the slanted well bore and the
substantially horizontal drainage pattern.
10. The method of claim 1, wherein the first, second, and third
entry well bores are spaced approximately twenty feet apart.
11. The method of claim 1, further comprising forming a second
horizontal drainage pattern from each of the slanted well bores
into a second subterranean zone.
12. A system for accessing a subterranean zone from the surface,
comprising: a first entry well bore extending from the surface; a
second entry well bore extending from the surface, the second entry
well bore located on the same drilling pad as the first entry well
bore at the surface; a third entry well bore extending from the
surface, the third entry well bore located on the same drilling pad
as the first and second entry well bores; one or more slanted well
bores extending from each of the first, second, and third entry
well bores to the subterranean zone; and a substantially horizontal
drainage pattern extending from the slanted well bores into the
subterranean zone.
13. The system of claim 12, wherein the horizontal drainage
patterns comprise a horizontal well bore extending from the slanted
well bore and a plurality of lateral well bores extending from the
horizontal well bore.
14. The system of claim 13, wherein the horizontal drainage
patterns comprise a crow's foot configuration.
15. The system of claim 13, wherein the lateral well bores are
configured to drain an area of the subterranean zone of at least
640 acres.
16. The system of claim 13, wherein the horizontal drainage
patterns comprise a pinnate configuration.
17. The system of claim 12, further comprising an enlarged cavity
in each of the slanted well bores proximate to the subterranean
zone.
18. The system of claim 12, further comprising an enlarged cavity
in each of the slanted well bores between the surface and the
horizontal drainage pattern.
19. The system of claim 17, wherein the enlarged cavity is located
proximate to the junction of the slanted well bore and the
substantially horizontal drainage pattern.
20. The system of claim 12, wherein the first, second, and third
entry well bores are spaced approximately twenty feet apart at the
surface.
21. The system of claim 12, further comprising a second
substantially horizontal drainage pattern extending from each
slanted well bore into a second subterranean zone.
22. A system for accessing a subterranean zone from the surface,
comprising: three or more entry well bores extending from the
surface; one or more slanted well bores extending from each entry
well bore to the subterranean zone; a substantially horizontal
drainage pattern extending from the slanted well bores into the
subterranean zone; and an enlarged cavity in each of the one or
more slanted well bores, located proximate to the junction of the
slanted well bore and the substantially horizontal drainage
pattern.
23. A system for accessing multiple subterranean zones from the
surface, comprising: three ore more entry well bores extending from
the surface; one or more slanted well bores extending from each
entry well bore to one or more subterranean zones; one or more
substantially horizontal drainage patterns extending from the
slanted well bores into each of the one or more subterranean zones;
and one or more enlarged cavities in each of the slanted well bores
positioned proximate to the junction of the slanted well bores and
the one or more of the substantially horizontal drainage
patterns.
24. The system of claim 23, wherein the three or more entry well
bores are located on the same drilling pad.
Description
RELATED PATENT APPLICATIONS
[0001] This application claims the priority benefit of U.S. patent
application Ser. No. 09/774,996 filed Jan. 30, 2001 entitled
"Method and System for Accessing a Subterranean Zone from a Limited
Surface Area."
[0002] This application is related to U.S. patent application Ser.
No. 10/004,316 entitled "Slant Entry Well System and Method" filed
on Oct. 30, 2001.
TECHNICAL FIELD OF THE INVENTION
[0003] The present invention relates generally to systems and
methods for the recovery of subterranean resources and, more
particularly, to a system and method for subterranean access.
BACKGROUND OF THE INVENTION
[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. Substantial
obstacles, however, have frustrated more extensive development and
use of methane gas deposits in coal seams. The foremost problem in
producing methane gas from coal seams is that while coal seams may
extend over large areas of up to several thousand acres, the coal
seams are fairly thin, varying from a few inches to several meters.
Vertical wells drilled into the coal deposits for obtaining methane
gas can only drain a fairly small radius around the coal deposits.
Further, coal deposits are not amenable to pressure fracturing and
other methods often used for increasing methane gas production from
rock formations. As a result, once the gas easily drained from a
vertical well bore in a coal seam is produced, further production
is limited in volume. Additionally, coal seams are often associated
with subterranean water, which must be drained from the coal seam
in order to produce the methane.
[0005] Horizontal drilling patterns have been tried in order to
extend the amount of coal seams exposed to a drill bore for gas
extraction. Such horizontal drilling techniques, however, require
the use of a radiused well bore which presents difficulties in
removing the entrained water from the coal seam. The most efficient
method for pumping water from a subterranean well, a sucker rod
pump, does not work well in horizontal or short radiused bores.
[0006] A single slanted well bore allows for effective water
removal via a sucker rod pump, capturing a benefit of a horizontal
well system, without limiting the use of horizontal drainage
patterns in the target zone.
SUMMARY OF THE INVENTION
[0007] The present invention provides a slant entry well system and
method for accessing a subterranean zone from the surface that
substantially eliminate or reduce the disadvantages and problems
associated with previous systems and methods. In particular,
certain embodiments of the present invention provide a slant entry
well system and method for efficiently producing and removing
entrained methane gas and water from a coal seam without requiring
excessive use of radiused or articulated well bores or large
surface area in which to conduct drilling operations.
[0008] In accordance with one embodiment of the present invention,
a system for accessing a subterranean zone from the surface
includes a first, second, and third entry well bore extending from
the surface, the first, second, and third entry well bores located
no more than one thousand feet away from each other at the surface.
A slanted well bore extends from each of the first and second entry
well bores to the subterranean zone. A substantially horizontal
drainage pattern extends from the slanted well bores into the
subterranean zone.
[0009] According to another embodiment of the present invention, a
method for accessing a subterranean zone from the surface includes
forming three or more closely spaced entry well bores and forming a
plurality of slanted well bores from the entry well bores to the
subterranean zone. The method also includes forming drainage
patterns from the slanted well bores into the subterranean zone and
enlarged cavities in the slanted well bores.
[0010] Embodiments of the present invention may provide one or more
technical advantages. These technical advantages may include the
formation of three or more closely spaced entry well bores, a
plurality of slanted well bores, and drainage patterns to optimize
the area of a subsurface formation which may be drained of gas and
liquid resources. This allows for more efficient drilling and
production and greatly reduces costs and problems associated with
other systems and methods. Another technical advantage includes
providing a method for accessing a subterranean zone from the
surface using a plurality of slanted well bores with one or more
enlarged cavities. The enlarged cavities allow for reduction of
velocity of gases escaping through the slanted well bores, aiding
in the removal of entrained liquids and optimizing the removal of
resources from the subterranean zone.
[0011] Other technical advantages of the present invention will be
readily apparent to one skilled in the art from the following
figures, descriptions, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a more complete understanding of the present invention
and its advantages, reference is now made to the following
description taken in conjunction with the accompanying drawings,
wherein like numerals represent like parts, in which:
[0013] FIG. 1 illustrates an example slant well system for
production of resources from a subterranean zone;
[0014] FIG. 2A illustrates a vertical well system for production of
resources from a subterranean zone;
[0015] FIG. 2B illustrates a portion of an example slant entry well
system in further detail;
[0016] FIG. 3 illustrates an example method for producing water and
gas from a subsurface formation;
[0017] FIG. 4 illustrates an example entry well bore;
[0018] FIG. 5 illustrates the use of an example system of an entry
well bore and a slanted well bore;
[0019] FIG. 6 illustrates an example system of an entry well bore
and a slanted well bore;
[0020] FIG. 7 illustrates an example system of a slanted well bore
and an articulated well bore;
[0021] FIG. 8 illustrates production of water and gas in an example
slant well system; and
[0022] FIG. 9 illustrates an example drainage pattern for use with
a slant well system.
DETAILED DESCRIPTION OF THE INVENTION
[0023] FIG. 1 illustrates an example slant well system for
accessing a subterranean zone from the surface. In the embodiment
described below, the subterranean zone is a coal seam. It will be
understood that other subterranean formations and/or zones can be
similarly accessed using the slant 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, to inject or introduce fluids, gases, or other
substances into the zone or for any other appropriate purpose.
[0024] Referring to FIG. 1, a slant well system 10 includes entry
well bores 15, slant wells 20, articulated well bores 24, cavities
26, and rat holes 27. Entry well bores 15 extend from the surface
11 towards the subterranean zone 22. Slant wells 20 extend from the
terminus of each entry well bore 15 to the subterranean zone 22,
although slant wells 20 may alternatively extend from any other
suitable portion of an entry well bore 15. As used herein, "each"
means all of a particular subset. Where there are multiple
subterranean zones 22 at varying depths, as in the illustrated
example, slant wells 20 extend through the subterranean zones 22
closest to the surface into and through the deepest subterranean
zone 22. Articulated well bores 24 may extend from each slant well
20 into each subterranean zone 22. One or more cavities 26 may be
located along a slant well 20 and a cavity 26 or a rat hole 27 may
be located at the terminus of each slant well 20.
[0025] In FIGS. 1, and, 4-8, entry well bores 15 are illustrated as
being substantially vertical; however, it should be understood that
entry well bores 15 may be formed at any suitable angle relative to
the surface 11 to accommodate, for example, surface geometries and
attitudes and/or the geometric configuration or attitude of a
subterranean resource. In the illustrated embodiment, each slant
well 20 is formed to angle away from entry well bore 15 at an angle
designated .alpha., which in the illustrated embodiment is
approximately 20 degrees. It will be understood that each slant
well 20 may be formed at other angles to accommodate surface
topologies and other factors similar to those affecting entry well
bores 15. In the illustrated embodiment, slant wells 20 are formed
in relation to each other at an angular separation of approximately
sixty degrees. It will be understood that slant wells 20 may be
separated by other angles depending likewise on the topology and
geography of the area and location of the target coal seam 22.
[0026] Entry well bores 15 are formed at the surface at a distance
of .beta. feet apart. In the illustrated embodiment, entry well
bores 15 are approximately twenty feet apart. It will be understood
that entry well bores 15 may be formed at other separations to
accommodate surface topologies and/or the geometric configuration
or attitude of a subterranean resource.
[0027] In some embodiments, entry well bores 15 may be between two
feet and one hundred feet apart. In some embodiments, the entry
well bores 15 may be located on the same drilling pad. As used
herein, "on the same drilling pad" means located at the same
drilling location where drilling operations are being conducted. In
some embodiments, entry well bores 15 are closely spaced together.
As used herein, "closely spaced" means on the same drilling
pad.
[0028] Cavities 26 may be formed at intervals along slant wells 20
above one or more of articulated well bores 24. For example,
cavities 26 may be formed immediately above an articulated well
bore 24. Cavities 26 may also be formed proximate to the junction
of slant well 20 and articulated well bore 24. As used herein,
proximate means immediately above, below, or at the junction of
slant well 20 and articulated well bore 24. It will be understood
that other appropriate spacing may also be employed to accommodate,
for example, sub-surface geometries and attitudes and/or the
geometric configuration or attitude of a subterranean resource.
Slant well 20 may also include a cavity 26 and/or a rat hole 27
located at the terminus of each slant well 20. Slant wells 20 may
include one, both, or neither of cavity 26 and rat hole 27.
[0029] FIGS. 2A and 2B illustrate by comparison the advantage of
forming slant wells 20 at an angle off the vertical. Referring to
FIG. 2A, a vertical well bore 30 is shown with an articulated well
bore 32 extending into a coal seam 22. As shown by the
illustration, fluids drained from coal seam 22 into articulated
well bore 32 must travel along articulated well bore 32 upwards
towards vertical well bore 30, a distance of approximately W feet
before they may be collected in vertical well bore 30. This
distance of W feet is known as the hydrostatic head and must be
overcome before the fluids may be collected from vertical well bore
30. Referring now to FIG. 2B, a slant entry well 34 is shown with
an articulated well bore 36 extending into coal seam 22. Slant
entry well 34 is shown at an angle a away from the vertical. As
illustrated, fluids collected from coal seam 22 must travel along
articulated well bore 36 up to slant entry well 34, a distance of
W' feet. Thus, the hydrostatic head of a slant entry well system is
reduced as compared to a substantially vertical system.
Furthermore, by forming slant entry well 34 at angle .alpha., the
articulated well bore 36 drilled from tangent or kick off point 38
has a greater radius of curvature than articulated well bore 32
associated with vertical well bore 30. This allows for articulated
well bore 36 to be longer than articulated well bore 32 (since the
friction of a drill string against the radiused portion is
reduced), thereby penetrating further into coal seam 22 and
draining more of the subterranean zone.
[0030] FIG. 3 illustrates an example method of forming a slant
entry well 20. The steps of FIG. 3 will be further illustrated in
subsequent FIGS. 4-8. The method begins at step 100 wherein an
entry well bore is formed. At step 105, a fresh water casing or
other suitable casing is installed into the entry well bore formed
at step 100. At step 110, the fresh water casing is cemented in
place inside the entry well bore of step 100.
[0031] At step 115, a drill string is inserted through the entry
well bore, and is used to drill approximately fifty feet past the
casing. In some embodiments, a short, radiused bore is formed. In
some embodiments, the radiused bore may be two hundred feet long
and articulate thirty-five degrees over its length. It will be
understood that other lengths and degrees may be employed based on
the local geology and topography. At step 120, the drill is
oriented to the desired angle of the slant well and, at step 125, a
slant well bore is drilled down into and through the target
subterranean zone. At step 130, one or more cavities are formed in
the slant well.
[0032] At step 135 the slant well casing is installed. Next, at
step 140, a short radius curve is drilled into the target coal
seam. Next, at step 145, a substantially horizontal well bore is
drilled into and along the coal seam. It will be understood that
the substantially horizontal well bore may depart from a horizontal
orientation to account for changes in the orientation of the coal
seam. Next, at step 150, a drainage pattern is drilled into the
coal seam through the substantially horizontal well. The drainage
pattern may comprise a pinnate pattern, a crow's foot pattern, or
other suitable pattern. At decisional step 155, a determination is
made whether additional subterranean zones are to be drained as,
for example, when multiple subterranean zones are present at
varying depths below the surface. If additional subterranean zones
are to be drained, the process repeats steps 140 through 155 for
each additional subterranean zone. If no further subterranean zones
are to be drained, the process continues to step 160.
[0033] At decisional step 160, a determination is made whether
additional slant wells are required. If additional slant wells are
required, the process returns along the Yes branch to step 100 and
repeats through step 155. A separate entry well bore may be formed
for each individual slant well bore. Thus, for each slant well, the
process begins at step 100, wherein a substantially vertical well
bore is found. In some embodiments, however, multiple slant wells
may be formed from one entry well bore.
[0034] If no additional slant wells are required, the process
continues along the No branch to step 165.
[0035] At step 165, production equipment is installed into each
slant well and at step 170 the process ends with the production of
water and gas from the subterranean zone.
[0036] Although the steps have been described in a certain order,
it will be understood that they may be performed in any other
appropriate order. Furthermore, one or more steps may be omitted,
or additional steps performed, as appropriate.
[0037] For example, where multiple target zones are present (as
determined at step 155), an enlarged diameter cavity may be found
(step 130) above each target zone before any of the short radius
curves are drilled (step 140). Alternatively, all of the short
radius curves may be found in each target zone (step 140) before
any enlarged diameter cavities are found (step 130). Other suitable
modifications will be apparent to one skilled in the art.
[0038] FIG. 4 illustrates entry well bore 15 and casing 44 in its
operative mode as a slant well 20 is about to be drilled.
Corresponding with step 110 of FIG. 3, a cement retainer 46 is
poured or otherwise installed around the casing inside entry well
bore 15. The cement casing may be any mixture or substance suitable
to maintain casing 44 in the desired position with respect to entry
well bore 15. A drill string 50 is positioned to begin forming a
slant well. In order to keep drill string 50 relatively centered in
casing 44, a stabilizer 52 may be employed. Stabilizer 52 may be a
ring and fin type stabilizer or any other stabilizer suitable to
keep drill string 50 relatively centered. To keep stabilizer 52 at
a desired depth in well bore 15, stop ring 53 may be employed. Stop
ring 53 may be constructed of rubber or metal or any other suitable
down-hole environment material.
[0039] FIG. 5 illustrates an example system of a slant well 20.
Corresponding with step 115 of FIG. 3, well bore 60 is drilled
approximately fifty feet past the end of entry well bore 15
(although any other appropriate distance may be drilled). Well bore
60 is drilled away from casing 44 in order to minimize magnetic
interference and improve the ability of the drilling crew to guide
the drill bit in the desired direction. As described above in
conjunction with FIG. 3, well bore 60 may also comprise an
articulated well bore with a radius of thirty-five degrees in two
hundred feet.
[0040] Corresponding with step 120 of FIG. 3, the drill bit is
oriented in preparation for drilling slant entry well bore 64.
Corresponding with step 125 of FIG. 3, a slant entry well bore 64
is drilled from the end of the radius well bore 62 into and through
the subterranean zone 22. Alternatively, slant well 20 may be
drilled directly from entry well bore 15, without including tangent
well bore 60 or radiused well bore. A rat hole 66, which is an
extension of slant well 64, is also formed. Rat hole 66 may also be
an enlarged diameter cavity or other suitable structure.
Corresponding with step 130 of FIG. 3, a cavity 26 is formed in
slant well 64.
[0041] Cavity 26 acts as a velocity reduction chamber, separating
entrained liquids from gasses destined for the surface. Without at
least one cavity 26 located closer to the surface than the
shallowest lateral well bore, entrained liquids form a mist that
raises down-hole pressure. Friction is increased by the liquids
entrained in escaping gasses, creating increased back pressure
(down-hole pressure). Reducing the gas velocity separates out the
liquid as the velocity drops below the speed at which the gas can
entrain liquids. Cavity 26 lowers the velocity of the gas enough to
separate out the entrained liquids, allowing the gas to proceed to
the surface more efficiently.
[0042] In the illustrated embodiment, cavity 26 is shown
immediately above the expected kick-off point for a subsequent
short radiused well bore. It will be understood that cavity 26 may
be otherwise suitably located. Moreover, it will be understood that
cavity 26 may also be formed after the horizontal drainage pattern
is formed.
[0043] FIG. 6 is an illustration of the positioning of the casing
in a slant well 64. For ease of illustration, only one slant well
64 is shown. Corresponding with step 135 of FIG. 3, a whipstock
casing 70 is installed into the slant entry well bore 64. In the
illustrated embodiment, whipstock casing 70 includes a whipstock 72
which is used to mechanically direct a drill string into a desired
orientation. It will be understood that other suitable techniques
may be employed and the use of a whipstock 72 is not necessary when
other suitable methods of orienting a drill bit through slant well
64 into the subterranean zone 22 are used. Whipstock casing 70 is
oriented such that whipstock 72 is positioned so that a subsequent
drill bit is aligned to drill into the subterranean zone 22 at a
desired depth.
[0044] FIG. 7 illustrates whipstock casing 70 and slant entry well
bore 64 in further detail. As discussed in conjunction with FIG. 6,
whipstock casing 70 is positioned within slant entry well bore 64
such that a drill string 50 will be oriented to pass through slant
entry well bore 64 at a desired tangent or kick off point 38. This
corresponds with step 140 of FIG. 3. Drill string 50 is used to
drill through slant entry well bore 64 at tangent or kick off point
38 to form articulated well bore 36. In a particular embodiment,
articulated well bore 36 has a radius of approximately seventy-one
feet and a curvature of approximately eighty degrees per one
hundred feet. In the same embodiment, slant entry well 64 is angled
away from the vertical at approximately ten degrees. In this
embodiment, the hydrostatic head generated in conjunction with
production is roughly thirty feet. However, it should be understood
that any other appropriate radius, curvature, and slant angle may
be used.
[0045] FIG. 8 illustrates a slant entry well 64 and articulated
well bore 36 after drill string 50 has been used to form
articulated well bore 36. In a particular embodiment, a horizontal
well and drainage pattern may then be formed in subterranean zone
22, as represented by step 145 and step 150 of FIG. 3.
[0046] Referring to FIG. 8, whipstock casing 70 is set on the
bottom of rat hole 66 to prepare for production of oil and gas. A
sealer ring 74 may be used around the whipstock casing 70 to
prevent gas produced from articulated well bore 36 from escaping
outside whipstock casing 70. Gas ports 76 allow escaping gas to
enter into and up through whipstock casing 70 for collection at the
surface. As described above, liquids entrained in the escaping gas
may be separated from the gas in enlarged diameter cavities 26
situated above the articulated well bore 36. As the liquids
separate from the gas, the liquids travel down slant well 64 and
are collected in rat hole 66. Rat hole 66 may also comprise an
enlarged diameter cavity (not shown) to collect liquids arriving
from above.
[0047] A pump string 78 and submersible pump 80 is used to remove
water and other liquids that are collected from the subterranean
zone through articulated well bore 36. As shown in FIG. 9, the
liquids, under the power of gravity and the pressure in
subterranean zone 22, pass through articulated well bore 36 and
down slant entry well bore 64 into rat hole 66. From there the
liquids travel into the opening in the whipstock 72 of whipstock
casing 70 where they come in contact with the installed pump string
78 and submersible pump 80. Submersible pump 80 may be a variety of
submersible pumps suitable for use in a down-hole environment to
remove liquids and pump them to the surface through pump string 78.
Installation of pump string 78 and submersible pump 80 corresponds
with step 165 of FIG. 3. Production of liquid and gas corresponds
with step 170 of FIG. 3.
[0048] FIG. 9 illustrates an example drainage pattern 90 that may
be drilled from articulated well bores 36. At the center of
drainage pattern 90 is a plurality of entry well bores 15 on a
drilling pad 92 at the surface. In one embodiment, entry well bores
15 are spaced approximately twenty feet apart. It will be
understood that other suitable spacings may also be employed.
[0049] Connecting to each entry well bore 15 is a slant well 20. At
the terminus of slant well 20, as described above, are
substantially horizontal well bores 94 roughly forming a "crow's
foot" pattern off of each of the slant wells 20. It will be
understood that any other suitable drainage patterns, for example,
a pinnate pattern, may be used. In an example embodiment, the
horizontal reach of each substantially horizontal well bore 94 is
approximately three hundred feet. Additionally, the lateral spacing
between the parallel substantially horizontal well bores 94 is
approximately eight hundred feet. In this particular embodiment, a
drainage area of approximately six hundred and forty acres would
result.
[0050] Although the present invention has been described with
several embodiments, various changes and modifications may be
suggested to one skilled in the art. It is intended that the
present invention encompass such changes and modifications as fall
within the scope of the appended claims.
* * * * *