U.S. patent application number 15/601460 was filed with the patent office on 2018-11-22 for pressure perforated well casing collar and method of use.
The applicant listed for this patent is Lloyd Murray Dallas. Invention is credited to Lloyd Murray Dallas.
Application Number | 20180334881 15/601460 |
Document ID | / |
Family ID | 64269512 |
Filed Date | 2018-11-22 |
United States Patent
Application |
20180334881 |
Kind Code |
A1 |
Dallas; Lloyd Murray |
November 22, 2018 |
PRESSURE PERFORATED WELL CASING COLLAR AND METHOD OF USE
Abstract
Pressure perforated well casing collars have at least one
pressure perforation groove cut to a consistent depth in a sidewall
of the well casing collar with sidewall bottom material at a bottom
of the groove. The sidewall bottom material ruptures at a
predetermined fluid pressure greater than a burst pressure rating
of plain casing joints connected to the well casing collars to
assemble a well casing string.
Inventors: |
Dallas; Lloyd Murray;
(Streetman, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dallas; Lloyd Murray |
Streetman |
TX |
US |
|
|
Family ID: |
64269512 |
Appl. No.: |
15/601460 |
Filed: |
May 22, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 17/006 20130101;
E21B 43/114 20130101; E21B 17/00 20130101 |
International
Class: |
E21B 34/06 20060101
E21B034/06; E21B 17/042 20060101 E21B017/042; E21B 17/08 20060101
E21B017/08; E21B 43/08 20060101 E21B043/08; E21B 43/267 20060101
E21B043/267; E21B 33/124 20060101 E21B033/124; E21B 33/14 20060101
E21B033/14; E21B 34/08 20060101 E21B034/08 |
Claims
1. A pressure perforated well casing collar, comprising: a pipe
having a sidewall with a first end, a second end, an inner surface,
an outer surface and a collar burst pressure rating; an internal
thread on each of the first and second ends adapted to threadedly
engage an external thread on a plain casing joint having a joint
burst pressure rating; at least one pressure perforation groove cut
in the outer surface, the at least one pressure perforation groove
extending inwardly from the outer surface to an extent less than a
thickness of the sidewall so there remains sidewall bottom material
in the at least one pressure perforation groove, the sidewall
bottom material having a rupture pressure rating that is greater
than the joint burst pressure rating; whereby isolated fluid
pressure applied within the pressure perforated well casing collar
will cause the sidewall bottom material in the at least one
pressure perforation groove to rupture before the collar burst
pressure rating is reached, thereby opening at least one
perforation through the sidewall of the well casing collar.
2. The pressure perforated well casing collar as claimed in claim
1, wherein the at least one pressure perforation groove is filled
with a coating compound to protect machined surfaces while the well
casing collar is in storage and while a casing string including the
well casing collar is being run into a recently drilled well
bore.
3. The pressure perforated well casing collar as claimed in claim 1
wherein the at least one pressure perforation groove has
overlapping ends.
4. The pressure perforated well casing collar as claimed in claim 3
wherein the at least on pressure perforation groove further
comprises at least one of a longitudinal and a transverse pressure
perforation groove within the at least one pressure perforation
groove having overlapping ends.
5. The pressure perforated well casing collar as claimed in claim 1
wherein the at least one pressure perforation groove is indexed to
the internal thread on the first end of the well casing collar so
that the at least one pressure perforation groove is always within
a 1/2 turn of a predetermined side of casing string when the well
casing collar is connected to the casing string and torqued to a
predetermined recommended torque.
6. The pressure perforated well casing collar as claimed in claim 5
further comprising a stamp on the outer surface of the well casing
collar indicating an orientation of the well casing collar in the
casing string and a side of the casing string on which at least one
pressure perforation groove will be when the well casing collar is
connected to the casing string and torqued to the predetermined
recommended torque.
7. The pressure perforated well casing collar as claimed in claim 1
further comprising at least one shallow internal identification
groove adjacent the internal thread.
8. A pressure perforated well casing system, comprising: well
casing collars respectively having a collar burst pressure rating,
each well casing collar having at least one pressure perforation
groove cut to a consistent depth in an outer surface thereof, the
at least one pressure perforation groove having sidewall bottom
material remaining in a bottom of the pressure perforation groove
and the sidewall bottom material having a rupture pressure rating;
a plain well casing joint having a joint burst pressure rating, the
joint burst pressure rating being less than the groove rupture
pressure rating; whereby after the well casing collars are used to
connect the plain casing joints to form a casing string that is run
into a recently drilled well bore, sufficient isolated fluid
pressure applied to the at least one pressure perforation groove of
a one of the well casing collars will cause the sidewall bottom
material in the at least one groove to rupture before the collar
burst pressure rating of the well casing collar is reached, thereby
opening at least one perforation through the sidewall of the well
casing collar at the at least one pressure perforation groove.
9. The pressure perforated well casing system as claimed in claim 8
wherein the at least one pressure perforation groove in the well
casing collar are straight grooves.
10. The pressure perforated well casing system as claimed in claim
8 wherein the at least one pressure perforation groove in the well
casing collar has ends that overlap.
11. The pressure perforated well casing system as claimed in claim
10 wherein the at least one pressure perforation groove further
comprises at least one of a longitudinal and a transverse pressure
perforation groove within the at least one pressure perforation
groove having overlapping ends.
12. The pressure perforated well casing system as claimed in claim
8 wherein the at least one pressure perforation groove is filled
with a coating compound to prevent corrosion of machined surfaces
and inhibit intrusion of cement when the casing string is cemented
in.
13. The pressure perforated well casing system as claimed in claim
8 wherein the well casing collars further comprise at least one
shallow internal identification groove detectable by a collar
locator.
14. A method of fracturing a subterranean production zone after a
well bore that penetrates the subterranean production zone has been
drilled, comprising: assembling a casing string comprising well
casing collars and plain well casing joints, the well casing
collars respectively having a collar burst pressure rating and at
least one pressure perforation groove cut to consistent depth in a
sidewall thereof, the at least one pressure perforation groove
having sidewall bottom material remaining in a bottom thereof, the
sidewall bottom material having a rupture pressure rating, and the
plain well casing joints having a joint burst pressure rating that
is less than the rupture pressure rating; running the casing string
into the well bore as it is assembled and cementing in the well
casing string after it is run into the well bore; running a
pressure isolation tool into the wellbore using a well completion
string; locating a one of the well casing collars and setting
uphole and downhole packers of the pressure isolation tool to
pressure isolate the well casing collar from the plain casing
joints; pumping high pressure perforation fluid down an annulus of
the well completion string and through a port in the pressure
isolation tool until the at least one pressure perforation groove
ruptures and opens at least one perforation through the well casing
collar; releasing the uphole and downhole packers of the pressure
isolation tool and moving the pressure isolation tool downhole of
the well casing collar; resetting at least one of the packers of
the pressure isolation tool; and pumping fracturing fluid down an
annulus of the casing string and through the at least one
perforation in the well casing collar to fracture the production
formation.
15. The method as claimed in claim 14 wherein the step of setting
at least one of the packers of the pressure isolation tool
comprises setting the uphole packer of the pressure isolation
tool.
16. The method as claimed in claim 14 wherein the step of setting
at least one of the packers of the pressure isolation tool
comprises setting the downhole packer of the pressure isolation
tool.
17. The method as claimed in claim 16 further comprising: while
pumping fracturing fluid down the annulus of the casing string,
simultaneously pumping fracturing fluid down the annulus of the
completion string though the port in the pressure isolation tool
and around the uphole packer into the at least one perforation in
the well casing collar.
18. The method as claimed in claim 17 wherein the fracturing fluid
pumped down the annulus of the casing string carries all the
proppant to be pumped through the at least one perforation in the
well casing collar.
19. The method as claimed in claim 14 wherein, when a screen-out
occurs, the method further comprises: ensuring the downhole packer
is set and the uphole packer is unset; and pumping fluid free of
proppant down the completion tubing through the port of the
pressure isolation tool and around the uphole packer to circulate
screened-out proppant uphole and out of the well bore.
20. The method as claimed in claim 14 further comprising the steps
of: releasing the at least one packer of the pressure isolation
tool and pulling up the pressure isolating tool to locate a next
well casing collar of the casing string; setting the uphole and the
downhole packers of the pressure isolation tool to pressure isolate
the well casing collar from the plain casing joints; pumping high
pressure perforation fluid down the well completion string and
through the port in the pressure isolation tool until the at least
one pressure perforation groove ruptures and opens at least one
perforation through the well casing collar; releasing the uphole
and downhole packers of the pressure isolation tool and moving the
pressure isolation tool downhole of the well casing collar;
resetting at least the uphole packer of the pressure isolation
tool; pumping fracturing fluid down an annulus of the casing string
and through the at least one perforation in the well casing collar
to fracture the production formation; and repeating these steps
until all of the well casing collars of the casing string have been
perforated and fracturing fluid has been pumped through al of the
perforations in the well casing collars.
Description
FIELD OF THE INVENTION
[0001] This Invention relates in general to hydrocarbon well casing
systems and, in particular, to a novel well casing collar that is
pressure perforated after a casing string is assembled, inserted
and cemented into a section of a recently drilled wellbore.
BACKGROUND OF THE INVENTION
[0002] Well casing is made up of casing joints and well casing
collars for connecting the casing joints together to assemble a
casing string. Well casing is commonly used to line recently
drilled hydrocarbon wellbores to prevent borehole collapse and
provide a smooth conduit for inserting tools required to complete
the well for production and produce hydrocarbon from the well. Most
hydrocarbon wells drilled today are vertical bores extending down
to proximity of a hydrocarbon production zone and horizontal bores
within the production zone. The vertical and the horizontal bores
are cased in a manner well known in the art after they are drilled.
The cased bore must be "completed" before hydrocarbon production
can commence. Completing a cased well bore generally involves
opening ports through the casing, followed by stimulating the
production zone that surrounds the open casing ports by injecting
high pressure fracturing fluids through the casing and into the
formation. There are many known methods used to complete a cased
well bore but only a few, such as the openhole multistage system
and plug-and-perf system, have achieved large-scale commercial
success. All known methods of cased well completion suffer from
certain drawbacks that are well understood by those skilled in the
art.
[0003] Applicant's U.S. patent application Ser. No. 15/469,821
filed Mar. 27, 2017 and entitled Pressure Perforated Well Casing
System describes a well casing system that overcomes many of the
problems associated with the completion of cased well bores. In
Applicant's well casing system, pressure perforated well casing
joints and/or pressure perforated well casing collars are assembled
into a casing string that is inserted into a well bore and pressure
perforated using high pressure fluid pumped from the surface after
the casing string has been cemented in the well bore. However,
additional research has now shown that even further improvements
are achievable.
[0004] There therefore exists a need for a novel well casing collar
that is pressure perforated after it is assembled in a well casing
string that is inserted and cemented into a section of a recently
drilled wellbore.
SUMMARY OF THE INVENTION
[0005] It is therefore an object of the invention to provide a well
casing collar that is pressure perforated after it is assembled
with plain casing joints into a well casing string that is inserted
into a section of a recently drilled wellbore and cemented in the
well bore.
[0006] The invention therefore provides a pressure perforated well
casing collar, comprising: a pipe having a sidewall with a first
end, a second end, an inner surface, an outer surface and a collar
burst pressure rating; an internal tread on each of the first and
second ends adapted to threadedly engage an external thread on a
plain casing joint having a joint burst pressure rating; at least
one pressure perforation groove cut in the outer surface, the at
least one pressure perforation groove extending inwardly from the
outer surface to an extent less than a thickness of the sidewall so
there remains sidewall bottom material in the at least one pressure
perforation groove, the sidewall bottom material having a rupture
pressure rating that is greater than the joint burst pressure
rating; whereby isolated fluid pressure applied within the pressure
perforated well casing collar will cause the sidewall bottom
material in the at least one pressure perforation groove to rupture
before the collar burst pressure rating is reached, thereby opening
at least one perforation through the sidewall of the well casing
collar.
[0007] The invention yet further provides a pressure perforated
well casing collar, comprising: a pipe having a sidewall with a
first end, a second end, an inner surface, an outer surface and a
collar burst pressure rating; an internal tread on each of the
first and second ends adapted to threadedly engage an external
thread on a plain casing joint having a joint burst pressure
rating; at least one pressure perforation groove cut in the outer
surface, the at least one pressure perforation groove extending
inwardly from the outer surface to an extent less than a thickness
of the sidewall so there remains sidewall bottom material in the at
least one pressure perforation groove, the sidewall bottom material
having a rupture pressure rating that is greater than the joint
burst pressure rating; whereby isolated fluid pressure applied
within the pressure perforated well casing collar will cause the
sidewall bottom material in the at least one pressure perforation
groove to rupture before the collar burst pressure rating is
reached, thereby opening at least one perforation through the
sidewall of the well casing collar.
[0008] The invention yet further provides a method of fracturing a
subterranean production zone after a well bore that penetrates the
subterranean production zone has been drilled, comprising:
assembling a casing string comprising well casing collars and plain
well casing joints, the well casing collars respectively having a
collar burst pressure rating and at least one pressure perforation
groove cut to consistent depth in an outer surface thereof, the at
least one pressure perforation groove having sidewall bottom
material remaining in a bottom thereof, the sidewall bottom
material having a rupture pressure rating, and the plain well
casing joints having a joint burst pressure rating that is less
than the rupture pressure rating; running the casing string into
the well bore as it is assembled and cementing in the well casing
string after it is run into the well bore; running a pressure
isolation tool into the wellbore using a well completion string;
locating a one of the well casing collars and setting uphole and
downhole packers of the pressure isolation tool to isolate the well
casing collar from the plain casing joints; pumping high pressure
perforation fluid down the well completion string and through a
port in the pressure isolation tool until the at least one pressure
perforation groove ruptures and opens at least one perforation
through the well casing collar; releasing the uphole and downhole
packers of the pressure isolation tool and moving the pressure
isolation tool downhole of the well casing collar; resetting the at
least one of the packers of the pressure isolation tool; and
pumping fracturing fluid down an annulus of the casing string and
through the at least one perforation in the well casing collar to
fracture the production formation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Having thus generally described the nature of the invention,
reference will now be made to the accompanying drawings, in
which:
[0010] FIG. 1 is a schematic view of an embodiment of a pressure
perforated well casing collar in accordance with the invention;
[0011] FIG. 2 is a schematic view of the well casing collar shown
in FIG. 1 connected to plain casing joints in a well casing
string;
[0012] FIG. 3 is a schematic cross-sectional view of the well
casing collar and the well casing joints shown in FIG. 2,
illustrating the use of a pressure isolation tool to perforate the
well casing collar shown in FIG. 1;
[0013] FIG. 4a is a schematic cross-sectional view of the well
casing collar and the well casing joints shown in FIG. 3,
illustrating a first method of fracturing a production zone using
the well casing collar in accordance with the invention;
[0014] FIG. 4b is a schematic cross-sectional view of the well
casing collar and the well casing joints shown in FIG. 3,
illustrating a second method of fracturing the production zone
using the well casing collar in accordance with the invention;
[0015] FIG. 5 is a schematic view of a another pressure perforated
well casing collar in accordance with the invention;
[0016] FIG. 6 is a schematic top plan view of an identification
stamp on a top surface of the well casing collar shown in FIG.
5;
[0017] FIG. 7 is a schematic view of a further pressure perforated
well casing collar in accordance with the invention;
[0018] FIG. 8 is a schematic top plan view of an identification
stamp on a top surface of the well casing collar shown in FIG.
7;
[0019] FIG. 9a is a detailed view of one embodiment of pressure
perforation grooves that may be used for the embodiments of the
well casing collar shown in FIGS. 5 and 7;
[0020] FIG. 9b is a cross sectional view taken along lines 9b-9b of
FIG. 9a;
[0021] FIG. 9c is a cross sectional view taken along lines 9c-9c of
FIG. 9a;
[0022] FIG. 10 is a schematic diagram of one embodiment of a casing
string assembled in accordance with the invention; and
[0023] FIG. 11 is a schematic diagram of a theoretical fracture
pattern of a subterranean production zone after it has been
fractured via a casing string assembled with well casing collars
shown in FIGS. 5 and 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The invention provides a pressure perforated well casing
collar that is used with plain casing joints to construct a well
bore casing. In this document "plain well casing joint" means any
API well casing pipe. The well casing collar has an outer sidewall
with at least one pressure perforation groove. A rupture pressure
of the at least one pressure perforation groove is higher than a
burst pressure of the plain casing joints, which determines a
maximum hydraulic fracturing pressure that can be used in the well.
Consequently, a well casing collar can be pressure perforated and
fracturing fluids can be pumped down the casing and through the
pressure perforated casing collar without danger of perforating any
other well casing collars uphole of the well casing collar just
perforated. This permits hydrocarbon wells to be completed and
fractured with greater efficiency and at less expense than prior
art casing and completion systems. The well casing collar in
accordance with the invention eliminates the need for sliding
sleeves, openhole packers, wirelines, perforating gun systems,
abrasive perforators, shaped charges, plugs and plug mills. In one
embodiment the well casing collar in accordance with the invention
also reduces the pump horsepower requirement for completing a well
by up to 60%, thus significantly reducing completion cost,
simplifying job scheduling and condensing a footprint required at
the wellhead. The well casing collar in accordance with invention
also significantly reduces fracturing crew idle time while
providing fracture location flexibility. The well casing collar in
accordance with invention may be used in vertical or horizontal
well bore completions and is equally effective and efficient in
either a vertical or a horizontal well bore.
[0025] FIG. 1 is a schematic view of an embodiment of a pressure
perforated well casing collar 10 in accordance with the invention.
The well casing collar 10 has a first end 12, a second end 14 and a
sidewall 18. An internal thread 16 cut within each of the first end
12 and the second end 14 is adapted to threadedly engage a plain
well casing joint, as will be discussed in more detail below with
reference to FIGS. 2-4 and 10. The well casing collar 10 has a
length "L" and an outside diameter "OD". The OD is dependent on the
size of plain well casing joints to be joined together to assemble
a casing string for insertion into a recently bored hydrocarbon
well bore. Typically, well casing is available in 4.5'' (11.4 cm),
5.5'' (13.97 cm), 7.5'' (19.05 cm) or 7.625'' (19.37 cm), although
3'' (7.62 cm), and several other diameters of well casing are
occasionally used. In accordance with the invention, the well
casing collar 10 is manufactured from suitable pipe having a burst
pressure rating (hereinafter "collar burst pressure rating") that
is significantly greater than a burst pressure rating of the plain
casing joints to be joined together using the well casing collar
10, as will be explained below in more detail with reference to
FIGS. 3 and 4a-b. The length "L" of the well casing collar 10 is a
matter of design choice, but in one embodiment the length "L" is
kept to a minimum in order to reduce cost in one embodiment the
length "L" is about 3' (91.4 cm), though shorter or longer well
casing collars 10 can be made for specific applications. At least
one pressure perforation groove 20 is cut into the sidewall 18. The
number and shape of the pressure perforation grooves 20 is
dependent on any one or more of: production formation
characteristics, hydrocarbon properties, and well operator choice.
The pressure perforation grooves 20 in this embodiment are shown to
be straight axial grooves, but the shape of the pressure
perforation grooves 20 is a matter of design choice. It is only
important that if more than one pressure perforation groove is cut,
the pressure perforation grooves 20 are spaced far enough apart
that any potential erosion (known in the art as "wash") from
fracturing operations is not likely to join two or more pressure
perforation grooves 20, which might compromise the strength of the
well casing collar 10.
[0026] In one embodiment, each pressure perforation groove 20 is
about 0.375''-0.5'' (1-1.27 cm) wide and 1''-3'' (2.5-7.6 cm) long.
The pressure perforation grooves 20 are not cut through the
sidewall 18. Rather, a predetermined thickness of sidewall bottom
material, explained below with reference to FIGS. 9a-9c, is left
between a bottom of each groove 20 and an inner wall 22 of the well
casing collar 10. The thickness of the sidewall bottom material is
calculated to have a predetermined rupture pressure (yield
strength). The predetermined rupture pressure is higher than a
burst pressure rating of plain casing joints connected together by
the well casing collar 10 to create a casing string. This has
distinct operational advantages that will be explained below with
reference to FIGS. 3, 4a, 4b and 11. When the sidewall bottom
material ruptures, at least one perforation is opened though the
collar sidewall 18 to provide access to a production formation.
Although the predetermined rupture pressure is greater than the
burst pressure rating of the plain casing joints, it is designed to
be less than the maximum fluid pressure potential of modern
fracturing pumps and completion tubing. Consequently, casing
strings assembled using the well casing collar 10 are very robust
and can be run into a recently bored well bore without hazard of
well bore material intrusion. The casing strings can also be
cemented in the well bore without danger of cement intrusion into
the casing string because cementing operation pressures rarely
exceed about 3,000 psi. Once the casing string is inserted into a
recently drilled well bore and cemented in, the well casing collars
10 can be selectively perforated using a downhole pressure
isolation tool which will be described, in principle only, with
reference to FIGS. 3, 4a and 4b.
[0027] FIG. 2 is a schematic view of the well casing collar 10
shown in FIG. 1 connected to plain casing joints 30a, 30b in a well
casing string, only a small proportion of which is shown. When used
with plain casing joints 30a, 30b the well casing collar 10
provides access to a production zone in which the casing string is
installed at intervals determined by a length of the plain casing
joints 30a, 30b and a frequency of use of the well casing collars
10, each of which is typically specified by a well consultant or
well operator. For example, a typical casing joint 30a, 30b is 40'
(12 m), an API Range 3 pipe. However, casing joints are available
in API Range 1 lengths (16' to 25') and API Range 2 lengths (25' to
34'). Consequently, a wide range of spacing options for the well
casing collars 10 is available using standard, plain well casing
joints.
[0028] FIG. 3 is a schematic cross-sectional view of the well
casing collar 10 and the plain casing joints 30a, 30b shown in FIG.
2, illustrating the use of a pressure isolation tool 40 to pressure
perforate the well casing collar 10 shown in FIG. 1. The
construction and operation of the pressure isolation tool 40 is
beyond the scope of this disclosure and will not be discussed in
any detail aside from the methods of using the pressure isolation
tool 40. In accordance with the invention, the pressure isolation
tool 40 is run into the cased well bore after the casing has been
cemented in and the cement has set, or partially set. In one
embodiment, a length of the pressure isolation tool 40 is less
than, or equal to, a length of the casing joint 10. The pressure
isolation tool 40 is run into the casing on a bottom end of a well
completion string 42. The well completion string 42 may be a coil
tubing string suitable for lateral bores shorter than the "push
limit" of coil tubing, or a jointed completion tubing string
suitable for both shorter and longer lateral bores, each of which
is well known in the art. The isolation tool 40 includes packers
44, 50 mounted to opposite ends of a high pressure mandrel 46
having at least on port 48 in fluid communication with the
completion tubing 42. The packers 44, 50 may be individually set
and released. Both packers 44, 50 are set after the pressure
isolation tool 40 is aligned with the well casing collar, which
alignment is readily determined using a collar locator (not shown),
well known to those skilled in the art. Because some plain casing
joints "torque up" to the casing collar 10 without leaving a gap
that is readily detectable by a collar locator, in one embodiment
of the well casing collar 10 a pair of shallow internal
identification grooves 24a, 24b are machined adjacent the internal
threads 16 (see FIG. 1). The shallow internal identification
grooves 24a, 24b are readily detectable by a collar locator, but
they do not compromise a strength or burst pressure rating of the
well casing collar 10.
[0029] After the packers 44, 50 are set, high pressure perforating
fluid is pumped down through the completion string 42 and the
pressure isolation tool port(s) 48. The high pressure perforating
fluid is contained between the set packers 44, 50 and isolated from
the plain casing joints 30a, 30b. In accordance with one embodiment
of the invention, the high pressure perforating fluid is fracturing
fluid that contains no proppant, though the composition of the high
pressure perforating fluid is a matter of design choice. Fluid
pressure of the high pressure perforating fluid is monitored at the
surface and pumping is initiated and continues until there is a
dramatic pressure drop in the pumped fluid, indicating that the
well casing collar has been perforated by the rupture of the
pressure perforation grooves 20. Monitoring the pump rate gives a
positive indication of the number of pressure perforation grooves
20 that have been ruptured.
[0030] FIG. 4a is a schematic cross-sectional view of the well
casing collar 10 and the well casing joints 30a, 30b shown in FIG.
3, illustrating a first method of fracturing a production zone
using the well casing collar 10 in accordance with the invention.
After the well casing collar 10 has been pressure perforated as
explained above with reference to FIG. 3, the pumping of high
pressure perforation fluid is terminated, the packers 44, 50 are
released and the pressure isolation tool 40 is moved downhole of
the well casing collar 10. The packers 44, 50 are then reset and
fracturing fluid (ff) is pumped down an annulus of the casing
string and through the newly formed slots 20b In the well casing
collar 10. In one embodiment, the fracturing fluid (if) is pumped
at a predetermined pressure that is generally near, but less than,
a burst pressure rating of the plain casing joints 30a, 30b. Since
the rupture pressure of uphole casing joints 10 is higher than the
burst pressure rating of the plain casing joints, there is no
danger that any of the well casing collars 10 uphole in the casing
string will be perforated while fracturing through perforations
just opened in a downhole well casing collar 10. The set packer 44
(uphole packer) prevents the fracturing fluid (ff) from migrating
downhole into zones previously fractured using this method in
accordance with the invention. Pumping down the annulus permits the
fracturing fluid to be pumped at a high rate, so the fracturing of
the production zone in communication with the slots 20b is
accomplished quickly. Since the volume of fracturing fluid that can
be pumped through the slots 20b is limited by the total open area
of those slots, the total pump horsepower required to pump the
fracturing fluid (ff) is up to 60% less than that required for most
sliding sleeve and plug-n-perf fracturing procedures, thus reducing
costs and surface footprint requirements.
[0031] FIG. 4b is a schematic cross-sectional view of the well
casing collar 10 and the well casing joints 32a, 32b shown in FIG.
3, illustrating a second method of fracturing the production zone
after the well casing collar 10 has been pressure perforated. In
this embodiment the pressure isolation tool 40 has been relocated
downhole, but only packer 50 (downhole packer) is set. Uphole
packer 44 is left in a relaxed, unset condition and fluid can be
pumped around it. Consequently, fracturing fluid (ff) is pumped
down the annulus of the casing string and through the newly formed
slots 20b in the well casing collar 10 while fracturing fluid (cf)
is pumped down the pressure isolation tool string 42 and through
the newly formed slots 20b in the well casing collar 10. This
provides a maximum fracturing fluid flow rate of that is
substantially equal to the pump rate that can be accomplished down
an open casing string. In one embodiment, the fracturing fluid
stream (ff) carries the entire proppant load into the production
zone while the fracturing fluid stream (cf) contains no proppant.
This permits circulation up the annulus of proppant-free fracturing
fluid pumped through the completion string 42 to remove a proppant
blockage in the event of a screen-out, which is well understood in
the art. In this embodiment, 2 or more shallow internal
identification grooves 24a, 24c and 24b, 24d are machined adjacent
the internal thread in each end of the casing collar 10. The two or
more shallow internal identification grooves 24a-24d are
respectively detectable by a collar locator and can be used for
identifying the well casing collars 10, as will be explained below
in more detail with reference to FIGS. 5 and 7.
[0032] FIG. 5 is a schematic view of another pressure perforated
well casing collar 50 in accordance with the invention, which
permits the practice of directional perforation. The well casing
collar 50 has a first end 52, a second end 54, an internal thread
56 in each of the first end 52 and the second end 54, and an outer
surface 58. In this embodiment at least one pressure perforation
groove is located on only one side of the well casing collar 50. In
one embodiment, first and second pressure perforation grooves 60a,
60b having overlapping ends are located on the one side of the well
casing collar 50. An identification stamp 62a on a top surface of
the well casing collar 50 identifies the side of the well casing
collar 50 with the pressure perforation groove(s) 60a, 60b.
Although two pressure perforation grooves 608, 60b are shown, this
is an example only. As explained above, the number of pressure
perforation grooves is dependent mainly, but not exclusively, on
formation characteristics. The pressure perforation grooves 60a,
60b are indexed to the internal thread 56 such that when the well
casing collar 50 is connected to a plain casing joint 90b (see FIG.
10) and is torqued to a recommended makeup torque, the orientation
of the pressure perforation grooves 60, 60b is consistently within
0.4 turn of any other well casing collar 50 having grooves cut in
the same location. The exact orientation of the well casing collar
50 on the casing joint 90b cannot be controlled due to variations
in an external thread on each end of the plain casing joints 90b.
Nonetheless, a rig operator assembling a casing string can
under-torque or over-torque the connection between a well casing
collar 50 and casing joint 90b by 1/2 turn to achieve a consistent
orientation of the well casing collar 50 on the plain casing joint
90b, without affecting the integrity of the casing string. The
advantages of this directional perforation will be explained below
with reference to FIGS. 10 and 11. In one embodiment, the casing
collar 50 can also be identified in a casing string after it is
inserted in a well bore by the number of shallow internal
identification grooves 24a-24d in the casing collar 50 detected by
a collar locator.
[0033] FIG. 6 is a schematic top plan view of one embodiment of the
identification stamp 62a on the top surface 58 of the well casing
collar 50 shown in FIG. 5. In one embodiment, the identification
stamp 62a Includes at least one arrow indicating a downhole
orientation of the well casing collar 50 and a letter indicating
that the pressure perforation grooves are on a given side of the
well casing collar 50 when it is connected to a casing string. In
this example, the letter "R" Indicates that the pressure
perforation grooves are on the right side of the well casing collar
50. This permits a rig crew to rapidly adjust a torque of the
connection, if required, to achieve the desired orientation as the
casing string is assembled and lowered into a wellbore.
[0034] FIG. 7 is a schematic view of a further pressure perforated
well casing collar 70 in accordance with the invention. The well
casing collar 70 is identical to the well casing collar 50, except
that the at least one pressure perforation groove(s) 80a, 80b is on
the left side of the well casing collar. Although two pressure
perforation grooves 80a, 80b are shown, this is an example only. As
explained above, the number of pressure perforation grooves is
dependent mainly, but not exclusively, on formation
characteristics. The well casing collar 70 has a first end 72, a
second end 74, an internal thread 76 in each of the first end 72
and the second end 74, and an outer surface 78. In this embodiment
the at least one pressure perforation groove is located on only the
left side of the well casing collar 70. An identification stamp 62b
on a top of the outer surface 78 indicates that. In one embodiment,
the casing collar 70 can also be identified in a casing string
after it is inserted in a well bore by the number of shallow
internal identification grooves 24a-24d in the casing collar 70
detected by a collar locator.
[0035] FIG. 8 is a schematic top plan view of the identification
stamp 62b on the top surface 78 of the well casing collar 70 shown
in FIG. 7. In one embodiment, the identification stamp includes at
least one arrow indicating a downhole orientation of the well
casing collar 70 and a letter "L", indicating that the pressure
perforation grooves are on the left side of the well casing collar
70 when it is connected to a casing string. This permits the rig
crew to rapidly adjust a torque of the connection, if required, to
achieve the desired orientation as the casing string is
assembled.
[0036] In practice, the well casing collars 50, 70 are connected to
respective plain casing joints at the recommended makeup torque to
assemble collar-50-plain-joint, collar-70-plain-joint combinations
that are placed in the pipe rack of the drill rig. The
collar-50-plain-joint, collar-70-plain-joint combinations are then
arranged in the pipe rack in alternating order so the rig crew has
to simply pick them up in order and connect them together while
making any minor torque adjustments required to maintain the
desired directional orientation of the pressure perforation grooves
as the casing string is inserted into the well bore.
[0037] FIG. 9a is a detailed view of one embodiment of pressure
perforation grooves that may be used for the embodiments of the
well casing collar shown in FIGS. 5 and 7. In this embodiment the
pressure perforation groove 80a In the outer surface 78 of the well
casing collar 70 (see FIG. 7) has an outer groove 82 with
overlapping ends. At least one pressure perforation groove 84
longitudinally bisects the rectangle defined by the outer pressure
perforation groove 82, and at least one pressure perforation groove
86 transversely bisects the rectangle defined by the outer pressure
perforation groove 82. Each of the pressure perforation grooves 82,
84 and 86 are cut to the same depth, leaving a thickness "B" (see
FIG. 9b) of sidewall bottom material. The thickness "B" of sidewall
bottom material may be calculated, for example, using a formula
(Formula 1) described on page 16 and 17 of American Petroleum
Institute Bulletin 5C3, Fifth Edition, July, 1989, incorporated
herein by reference, to achieve the desired rupture pressure of the
sidewall bottom material. The formula is:
P.sub.y=0.7854(D.sup.2-d.sup.2)Y.sub.p (Formula 1)
[0038] where: P.sub.y=pipe body yield strength in pounds rounded to
nearest 1000; [0039] Y.sub.p=Specified minimum yield strength for
pipe, psi; [0040] D=specified outside diameter, inches; [0041]
d=specified inside diameter, inches.
[0042] FIG. 9b is a cross sectional view taken along lines 9b-9b of
FIG. 9a showing the pressure perforation grooves 82, 86. In one
embodiment the pressure perforation grooves 82, 86 are filled with
a coating compound 88 designed to protect the machined surfaces
while the well casing collar 10, 50 or 70 is in storage and while
it is being run into a recently drilled well bore. The coating
compound 88 also prevents the intrusion of cement into the pressure
perforation grooves but remains soft to facilitate rupture of the
sidewall bottom material under fluid pressure. Such coating
compounds are available, for example, from Masterbond, Hackensack,
N.J., U.S.A.
[0043] FIG. 9c is a cross sectional view taken along lines 9c-9c of
FIG. 9a showing groove 82 and 84 filled with coating compound 88.
The advantage of the longitudinal pressure perforation groove 84
and transverse pressure perforation groove 86 is that the
intersection of those grooves is the weakest point in the sidewall
78 of the well casing collar 70. Consequently rupture occurs there
first, driving the resulting four sharp points of the ruptured
steel through the well bore cement before the entire perforation
tears away from the sidewall 78 of the casing joint 70 and breaks
up the well bore cement as the four segments are driven into the
formation behind the well bore cement.
[0044] FIG. 10 is a schematic diagram of one embodiment of part of
a casing string assembled in accordance with one embodiment of the
invention. In this embodiment a plain casing joint 92a is connected
to a top end of the well casing collar 50; a plain casing joint 92b
is connected to a bottom end of well casing collar 50 and a top end
of well casing collar 70; and, a plain well casing collar 90c is
connected to a bottom end of the well casing collar 70. The entire
casing string is assembled in this fashion, alternating well casing
collars 50 and 70 so that the pressure perforations are on opposite
sides of the casing string as it is lowered into the wellbore.
Although the downhole orientation of the casing string cannot be
guaranteed, the in-string orientation of perforations alternating
on opposite sides of the casing string can be ensured, as can the
proper orientation of the casing string as it enters the wellbore.
The benefits of this oriented perforation will be explained below
with reference to FIG. 11.
[0045] FIG. 11 is a schematic diagram of a theoretical fracture
pattern of a proportion of a subterranean production zone 100 after
it has been fractured via a casing string assembled with plain
casing joints and well casing collars 50, 70 shown in FIGS. 5 and
7. Plain casing joints are interconnected by well casing collars
50, 70 in an alternating pattern as follows: casing joint 102a,
well casing collar 50, casing joint 102b, well casing collar 70,
casing joint 102c, well casing collar 50, casing joint 102d, well
casing collar 70, casing joint 102e, etc. A distance between the
well casing collars 50, 70 is dependent on a length of the plain
casing joints 102. The length of the plain casing joints is a
design choice, which may be production formation dependent and
selected by a production consultant or well operator. Furthermore,
plain casing joints of the same length need not be used throughout
any given casing string. This provides a great deal of flexibility
in determining a location of fracture propagation points in the
formation. Since most production zones extend horizontally in a
relatively narrow band, it is advantageous to have the fractures
propagate laterally of the casing string. This can be readily
achieved using the well casing collars 50, 70 in accordance with
the invention. Furthermore, since the casing string is cemented in
before it is perforated, each fracture propagation point is
guaranteed and is not a matter of chance. In shale formations, for
example, it is likely that fractures 104 will propagate in both
directions from the pressure perforation points provided by the
well casing collars 50, 70. The fractures 104 will generally
propagate until they begin to interconnect with downhole fractures
104 previously propagated. Fracture interconnection is indicated at
surface by a pressure drop in the fracturing fluid, indicating that
fracturing through a well casing collar 50, 70 can be
terminated.
[0046] The well casing collars 10, 50 and 70 in accordance with the
invention are ideally adapted for use in modern production
techniques such as described in Applicant's U.S. Pat. No. 9,644,463
which Issued May 9, 2017, the entire specification of which is
incorporated herein by reference.
[0047] In fact, the casing collars 10, 50, 70 can be used in novel
ways to produce hydrocarbons from long lateral well bores. Using
the shallow internal identification grooves 24a-24d (see FIG. 4b,
for example) to identify alternate casing collars 10, a long
lateral well bore can be completed by pressure perforating every
second casing collar 10. After production from the well bore is no
longer economically viable, the unperforated casing collars can be
located using the shallow internal identification grooves 24a-24d.
Those unperforated casing collars can then be perforated in
sequence and stimulation fluids pumped through the newly perforated
casing collars 10, after which the long lateral well bore can once
more be produced.
[0048] In another variation, the shallow internal identification
grooves may be used to distinguish well casing collars 50 from well
casing collars 70. This permits a first side (for example, casing
collars 50) of a long lateral well bore to be completed and
produced while the opposite side (for example, casing collars 70)
is left unperforated and not produced. After hydrocarbon production
from the first side of the long lateral wellbore is complete, the
remaining casing collars (casing collars 70 in this example) are
perforated in sequence and fractures are propagated from each
perforated casing collar. Production of hydrocarbons from the
opposite side of the long lateral well bore can then commence. Of
course these novel methods can be used on any proportion of a long
lateral wellbore at a time.
[0049] The explicit embodiments of the invention described above
have been presented by way of example only. The scope of the
invention is therefore intended to be limited solely by the scope
of the appended claims.
* * * * *