U.S. patent application number 14/520202 was filed with the patent office on 2015-05-14 for slim-line casing centralizer.
The applicant listed for this patent is WWT North America Holdings, Inc.. Invention is credited to Sarah Mitchell, Norman Bruce Moore.
Application Number | 20150129200 14/520202 |
Document ID | / |
Family ID | 53042040 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150129200 |
Kind Code |
A1 |
Moore; Norman Bruce ; et
al. |
May 14, 2015 |
SLIM-LINE CASING CENTRALIZER
Abstract
A casing centralizer having a multiplicity of support fingers
positioned on a body of the casing centralizer each finger formed
into a collapsible spring configured to support a predetermined
load at an apex of the finger, each finger having a leading forward
angle positioned downhole and a following aft angle positioned
uphold and a landing tab positioned on an end of the finger
adjacent the aft angle, the body includes a finger pocket which
guides the landing tab with the finger collapses due to side
loads.
Inventors: |
Moore; Norman Bruce; (Aliso
Viejo, CA) ; Mitchell; Sarah; (Corona, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WWT North America Holdings, Inc. |
Houston |
TX |
US |
|
|
Family ID: |
53042040 |
Appl. No.: |
14/520202 |
Filed: |
October 21, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61902091 |
Nov 8, 2013 |
|
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Current U.S.
Class: |
166/241.6 |
Current CPC
Class: |
E21B 17/1028 20130101;
E21B 17/00 20130101; E21B 17/1078 20130101 |
Class at
Publication: |
166/241.6 |
International
Class: |
E21B 17/10 20060101
E21B017/10; E21B 17/00 20060101 E21B017/00 |
Claims
1. A casing centralizer having a multiplicity of support fingers
positioned on a body of the casing centralizer, each support finger
is formed into a collapsible spring configured to support a
predetermined load at an apex of the support finger, each support
finger having a leading forward angle positioned downhole and a
following aft angle positioned uphole and a landing tab positioned
at an end of the support finger adjacent the aft angle, the body
having a finger pocket which guides the landing tab when the
support finger collapses due to side loads.
2. The centralizer of claim 1 further comprising a stop collar
positioned at opposite ends of the body.
3. The centralizer of claim 1 configured to be positioned around an
outside diameter of a first casing and within an annular opening
between the first casing and a larger diameter second casing.
4. The centralizer of claim 1 wherein the body is made of tempered
steel, a low modulus high strength metal or fiber-epoxy
composite.
5. The centralizer of claim 1 wherein the body is coated with a low
friction material.
6. The centralizer of claim 5 wherein the low friction material
includes urethane, ultra-high molecular weight polyethylene,
Teflon.RTM. or PFA.
7. The centralizer of claim 1 wherein the support fingers are of
different sizes.
8. The centralizer of claim 1 wherein the leading forward angle and
the following aft angle range from about 15 to 85 degrees.
9. The centralizer of claim 8 wherein the leading forward angle and
the following aft angle are different sizes.
10. The centralizer of claim 1 wherein the support fingers provide
a variable amount of side load support.
11. An apparatus for centralizing well bore casing comprising: a
first casing extending within a bore hole of a well; a second
casing surrounding the first casing creating an annular space
therebetween; a casing centralizer positioned around the first
casing in the annular space having a multiplicity of support
fingers positioned on a body portion, each support finger formed
into a collapsible spring configured to support a predetermined
load at an apex of the support finger, each support finger having a
leading forward angle position downhole and a following aft angle
positioned uphold, the support fingers configured to collapse when
exposed to the predetermined load; and a stop collar is positioned
at opposite ends of the body around the first casing.
12. The apparatus of claim 11 wherein the support fingers include a
landing tab positioned on an end of each support finger adjacent
the aft angle and wherein the body includes a finger pocket which
guides the landing tab when the support finger collapses.
13. The apparatus of claim 11 wherein the casing centralizer is
made of tempered steel, a low modulus high strength metal or
fiber-epoxy composite.
14. The apparatus of claim 11 wherein the casing centralizer is
coated with a low friction material.
15. The apparatus of claim 11 wherein the support fingers are of
different sizes.
16. The apparatus of claim 11 wherein the support fingers are of an
increasing height moving towards a center of the body portion.
17. The apparatus of claim 11 wherein the leading forward angle and
the following aft angle range from about 15 to 85 degrees.
18. The apparatus of claim 17 wherein the leading forward angle and
the following aft angle are different sizes.
19. The apparatus of claim 11 wherein the support fingers provide a
variable amount of side load support.
20. The apparatus of claim 14 wherein the low friction material
includes urethane, ultra-high molecular weight polyethylene,
Teflon.RTM. or PFA.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims the benefit of and priority to U.S.
Provisional Application No. 61/902,091, filed Nov. 8, 2013, the
contents of which are incorporated herein in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates to gas and oil production, and more
particularly to improvements in casing centralization.
BACKGROUND
[0003] To obtain pressure integrity and structural adequacy,
typically after an oil or gas well is drilled the hole is lined
with steel pipe and cement is inserted between the pipe and the
formation. The centering of the casing within the hole is performed
by casing centralizers of various types. Many casing centralizer
types exist including fixed diameter solid cast or molded types
with various types of thin-like extensions such as cords or
spiral-shaped, bow-spring types that are self or double bow with
welded and non-welded bows made of various material including zinc,
steel, and plastic.
[0004] Casing centralization is of importance to oil and gas wells
because proper centralization of the casing within the hole leads
to improved cementing of the casing, and hence, pressure, integrity
and safety. Centralizers are also important to allow use of slotted
liners to avoid slot plugging, reduce drag during installation, and
limit differential sticking of the casing to the formation during
installation.
[0005] Historically, many different attempts were made to satisfy
the multiple requirements for proper casing centralization; but
these have failed because only one or two of the performance
requirements were satisfied in previous designs. Requirements
include the need to keep the casing in the center of the hole and
allowing the cement to be evenly distributed around the casing.
This centralization is difficult because of well bore configuration
and common drilling problems. For example, in non-vertical wells,
such as extended reach wells or horizontal wells, the casings
weight forces the casing to the low side of the hole; without
centralization, the casing will sit on the bottom side of the hole
and prevent proper cementation. Further, certain drilling
curvatures in the well bore trajectory caused by variations in rock
hardness and orientation; these are commonly called "dog-legs," and
can result in the casing contacting the whole wall in a
non-concentric manner.
[0006] Also, part of casing centralization is efficient passage of
the cement past the centralizer towards the surface. If the
centralizer fills a significant portion of the annulus between the
casing and the well bore, the result is restriction of the cement
flow, thus requiring greater pumping, but more incomplete cement
coverage.
[0007] Another common problem occurs when running a smaller casing
liner through a casing exit without a whipstock in place. For these
applications, failure of the centralizers run on liners through
casing exits can result in expensive time lost due to fishing
(retrieving parts) and milling of pieces of centralizers in order
to obtain proper well function. This significant problem is
associated with the transition across the sharp edge of the casing
and into open hole.
[0008] When drilling oil and gas wells in deep water locations such
as in the Gulf of Mexico and offshore Brazil, contingency planning
frequently involves the drilling string design with many concentric
casing. Post Macondo accident in the Gulf of Mexico, various
governmental regulatory agencies and industry associations have
required more contingency planning that has resulted in increased
number of casing strings that have outside diameters that allow
less space between the formation and the casing for cement.
[0009] One of the methods to allow contingency planning for
additional casing strings is to drill out from one casing with an
under-reamer thus producing a drilled hole that is larger than the
inside diameter of the casing the under-reamer passes through. For
example, a centralizer installed on a 113/4 inch casing application
may be required to pass through (i.e. collapse) from 123/8 inch and
expand to 141/2 inch and support 1,000 pounds of side load.
Consequently, a need exists for a centralizer that can run between
two well casings having a relatively narrow annular space between
casings. Such an application eliminates the use of fixed diameter
centralizers because they cannot expand or contract through the
restrictions. Further, existing bow-type centralizers do not
provide enough side load support, and hence when used will
collapse, thus not providing a centralized pipe and may result in a
poor or even unsafe cement bond between the casing and the
formation. Hence, there exists a need for a centralizer with
limited expansion and collapse capability but with high amounts of
side load support capability.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to a slim-line casing
centralizer having limited expansion and collapse capability but
with high amounts of side load support capability. The slim-line
casing centralizer of the present invention includes three
components including a top and a bottom stop collar positioned
above and below a centralizer sleeve. The centralizer body or
sleeve is typically made of steel that is quenched and tempered to
produce a high strength spring-steel-like behavior. Alternatively,
the centralizer body or sleeve can be made of a low modulus
high-strength metal such as titanium or a specially designed
fiber-epoxy composite. The centralizer body can have a coating of
low friction materials. The centralizer body consists of a
multiplicity of support fingers, each finger is formed into a
collapsible spring. Each finger is shaped to support a
predetermined load at its apex. The shape is approximated by the
performance of a beam and consists of a leading forward angle
(downhole), a following aft angle (uphole). Typically the forward
and downward angle range from 15 to 85 degrees, but most typically
are forty-five degrees. The forward and aft angles are not
necessarily the same. The end of the support fingers consist of a
landing tab. When the centralizer experiences radial loads, the
support finger collapses into a finger pocket. The pocket is sized
to allow the complete collapse of the support finger. The landing
tab guides the spring finger into its collapse without interference
with the body of the centralizer.
[0011] These and other features and advantages of the present
invention will be more fully understood by reference to the
following detailed description in connection with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-sectional view of a formation illustrating
the slim-line casing centralizer of the present invention
positioned between two casing sections;
[0013] FIG. 2 is a front view of the centralizer of FIG. 1 as
installed on a casing;
[0014] FIG. 3 is a perspective view of a stop collar of the
centralizer of FIG. 1; and
[0015] FIG. 4 is a perspective view of the centralizer body or
sleeve of the present invention.
DETAILED DESCRIPTION
[0016] FIG. 1 is a cross sectional view of a slim-line casing
centralizer 10 positioned in the narrow annular space between
casings 12 and 14 located within a bore hole 16 drilled within an
underground formation 18. As shown in FIG. 2, the casing
centralizer 10 consists of a centralizer sleeve 20 and top and
bottom stop collars 22 and 24. As also shown in FIG. 3, stop
collars are typically made of steel or aluminum or other metal and
include holes 26 for the insertion of steel set screws 28 which
when turned apply a griping force from the collar to the inner
casing 14.
[0017] As also can be seen in FIG. 4, the centralizer body or
sleeve 20 is typically made of a sheet of steel that is quenched
and tempered to produce a high strength spring-steel-like behavior.
Alternatively, the centralizer body can be made of a low modulus
high strength metal such as titanium or a specially designed
fiber-epoxy composite.
[0018] The centralizer body can include a coating of low friction
materials to prevent wear on the casing. The coating may be
urethane or an epoxy filled with ultra-high molecular weight
polyethylene. These coatings reduce wear as well as rotating
friction. The casing itself can also be coated. The coating can
also include Teflon.RTM. (PTFE polytetrafluoroethylene) or PFA
(perfluoroalkoxy alkanes).
[0019] The centralizer sleeve is made into a continuous cylindrical
body 30 by rolling the sheet metal and welding the ends 32
together. A plurality of finger support elements 34 are cut into
the body 30 uniformly along the body. The finger support elements
are cut into the body to include gaps for the finger elements to
function. Each support finger 34 is formed into a collapsible
spring. Each finger is shaped to support a pre-determined load at
its apex 36. The shape of the finger is approximated by the
performance of a beam and consists of a leading forward angle 38
and a following aft support angle 40. Typically, the forward and
aft angles range from about 15 to about 85 degrees, but most
typically are 45 degrees. The forward and aft angles are not
necessarily the same. The end of the support fingers consists of a
landing tab 42. When the centralizer experiences radial loads, the
support fingers collapse with the landing tab 42 extending into a
finger pocket 44. The finger pocket is sized to allow the complete
collapse of the support finger. The landing tab guides the support
finger into its collapse without interference with the body of the
centralizer which prevents the support fingers from snagging on
surfaces during sliding into the hole.
[0020] Although manufacturing convenience would indicate that the
support fingers were the same size, it is not necessary.
Specifically, the support fingers can be of different sizes to
facilitate running in the hole. In one embodiment, the support
fingers are of increasing height moving to the center of the sleeve
from either end. This embodiment helps reduce snagging during
running. Further, a variable amount of side load support may be
useful in applications where dogleg severity changes abruptly.
[0021] The number and dimensions of the support fingers are
adjusted according to the anticipated side loads on the centralizer
at the time of installation. Because of the multiplicity of support
fingers, which could range from about 10 to 100, each finger
contributes to the side load capacity of the centralizer. For
example, in a 14 inch diameter configuration, made from 0.05 inch
thick steel with yield strength of 150,000 psi, a forward angle of
45 degrees, an aft angle of 30 degrees, a 0.5 inch wide finger with
a 0.5 inch space between fingers, a 3 inch collapsed length, can
support approximately 22 pounds side force per finger that is
normally loaded. As fingers that are not readily under the side
load, a percentage of the normal load is proportional to the angle
of the load to the transfer axis of the casing. For an application
that requires 1500 pound side load will require a centralizer that
is approximately 68 inches long.
[0022] Table 1 provides dimensional requirements for the slim-line
casing centralizer examples of the present invention for various
casing sizes.
TABLE-US-00001 Slim Line Slim Line Prior Casing Size Prior Casing
Centralizer Centralizer Slim Line Centralizer Size Pass Casing
Inside Expanded Out- Must Pass Through Through Inside Diameter side
Diameter (OD & Wt./ft.) Diameter (inches) (inches) (inches
& lb./ft.) (inches) 5 6.5 7'' & 38# 5.92 5.5 7 75/8'' 47.1#
6.375 7 9.875 93/8'' 39# 8.575 7.625 11.5 95/8'' 40# 8.835 8.625
11.5 113/4'' 78.80# 10.438 9.375 12.25 113/4'' 82.6# 10.368 9.625
12.25 113/4'' 65# 10.682 11.75 14.5 133/8'' 72# 12.347 11.875 14.5
14'' 105# 12.532
[0023] Using American Petroleum Institute API (API) Specification
10D/ISO 10427-1-2001 for centralizers, the above method and
modifying the materials, material thickness, width and length of
fingers, finger forward and aft angles, number of fingers on the
circumference, number of rings of fingers can be changed to meet
any size of casing centralizer side load requirement. This process
can be done in a closed form calculation or with iterative finite
element analyses.
[0024] For example, in Table 1 of the API-Specification 10D for a
51/2 inch casing the minimum restoring force (a radial force) at
67% standoff (67% of the cross-sectional area of the hole is filled
by the centralizer) is 620 pound and a maximum 620 pound starting
force (axial sliding). For a 51/2 inch slim line centralizer, the
restoring radial force is approximately 800 pounds and the maximum
axial sliding starting force in formation is approximately 325
pounds. Lower starting forces advantageous for starting to run
casing and a higher standoff force is advantageous, especially for
inclined or horizontal wells, which the slim line casing
centralizer of the present invention achieves.
[0025] The number of centralizers placed on a casing string can
vary from about 5 to about 200 depending upon the well inclination
and casing size and weight, dog-leg severity, and other well
completion parameters. The side loads can be estimated by current
commercially available software packages. Typically, each well is
analyzed and specific recommendations per well are made.
[0026] Benefits of the slim-line casing centralizer of the present
invention include centralization in narrow openings between
individual casing. This allows for centralization between casing
when the annular space is limited such as when running contingency
casing strings in offshore applications. Utilizing a high forward
angle or aft angle (from about 15 to about 85 degrees) in the
support fingers allows the largest amount of support per finger and
when combined with a large number of fingers within sheet metal
construction, the result is an extremely slim structure with high
collapse resistance and low drag resistance. A large number of
support fingers that have wide range of expansion and collapse
configurations allows the centralizer to be flexible to anticipated
side load conditions. The centralizer of the present invention is
scalable for casing between 41/2 inches and 16 inches in outside
diameter. Because there are a large number of support fingers, if
any single one is snagged during the running process, the loss of
an individual or severed finger does not significantly inhibit
running the casing nor does it significantly affect the drag during
installation. By changes to the forward angle and the aft angle of
the support fingers, the expansion from full expanded to collapsed
can be adjusted. By changing the expanded height of the support
fingers a gradient of height facilitates running of the centralizer
with fewer hang ups. The slim-line casing centralizer of the
present invention typically exceeds the API 10D minimum radial
standoff force and is typically less than the maximum starting
force; from filling both of these requirements facilitates
centralization in inclined holes and ease of running.
[0027] Although the present invention has been described with
respect to a preferred embodiment thereof, it is to be understood
that changes and modifications can be made therein which are within
the full intended scope of the invention as hereinafter
claimed.
* * * * *