U.S. patent application number 11/793670 was filed with the patent office on 2008-05-15 for method of sealing an annular space in a wellbore.
Invention is credited to Martin Gerard Rene Bosma, Erik Kerst Cornelissen, Mikhail Boris Geilikman.
Application Number | 20080110628 11/793670 |
Document ID | / |
Family ID | 34930921 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080110628 |
Kind Code |
A1 |
Bosma; Martin Gerard Rene ;
et al. |
May 15, 2008 |
Method of Sealing an Annular Space in a Wellbore
Abstract
A method is provided of sealing an annular space between an
expandable tubular element arranged in a wellbore and a wall
surrounding the expandable tubular element. A pressure difference
occurs between a first location in the annular space and a second
location in the annular space axially spaced from the first
location. The method comprises: installing the tubular element in
the wellbore; locating a body of fluid in the annular space between
the first and second locations, the fluid having a yield strength
selected such that the pressure difference is insufficient to
induce axial flow of the body of fluid in the annular space after
radial expansion of the tubular element; and radially expanding the
tubular element.
Inventors: |
Bosma; Martin Gerard Rene;
(Assen, NL) ; Cornelissen; Erik Kerst; (Rijswijk,
NL) ; Geilikman; Mikhail Boris; (Rijswijk,
NL) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Family ID: |
34930921 |
Appl. No.: |
11/793670 |
Filed: |
December 13, 2005 |
PCT Filed: |
December 13, 2005 |
PCT NO: |
PCT/EP05/56716 |
371 Date: |
October 4, 2007 |
Current U.S.
Class: |
166/295 |
Current CPC
Class: |
E21B 43/103 20130101;
E21B 33/10 20130101; C09K 8/44 20130101; C04B 26/04 20130101; E21B
33/14 20130101; C04B 24/38 20130101; C04B 14/10 20130101; C04B
26/04 20130101; C04B 14/104 20130101; C09K 8/422 20130101 |
Class at
Publication: |
166/295 |
International
Class: |
E21B 33/13 20060101
E21B033/13 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2004 |
EP |
04257820.3 |
Claims
1. A method of sealing an annular space formed between an
expandable tubular element arranged in a wellbore having a wellbore
wall and a wall surrounding the expandable tubular element, whereby
a pressure difference occurs between a first location in the
annular space and a second location in the annular space axially
spaced from the first location, the method comprising: installing
the tubular element in the wellbore; locating a body of fluid in
the annular space between said first and second locations, said
fluid having a yield strength selected such that said pressure
difference is insufficient to induce axial flow of the body of
fluid in the annular space after radial expansion of the tubular
element; and radially expanding the tubular element.
2. The method of claim 1, wherein said body of fluid is at least
partly located in the annular space by pumping said fluid via the
tubular element before expansion thereof, into the annular
space.
3. The method of claim 1, wherein said body of fluid is at least
partly located in the annular space by the step of radially
expanding the tubular element.
4. The method of claim 1, wherein said wall is the wellbore
wall.
5. The method of claim 1, any one of claims 1, wherein said fluid
is a non-hardening fluid.
6. The method of claim 1, wherein said fluid is a thixotropic
fluid.
7. The method of claim 1, wherein said fluid is selected from the
group consisting of a Bingham Plastic and a Herschel Bulkley
fluid.
8. The method of claim 1, wherein said fluid is a gel.
9. The method of claim 8, wherein the gel comprises at least one of
a chromium cross-linked polyacrylamide, a polymer cross-linked by a
backbone of carbon atoms, a synthetic layered silicate clay, an
oleophilic based clay packer gel, an oil based thermal insulating
gel, an in situ gelleable composition, a thermoset synthetic gel,
and a modified xantham gum.
10. The method of claim 9, wherein the gel comprises a polymer
cross-linked by a backbone of carbon atoms, and wherein said
backbone of carbon atoms comprises groups capable of forming bonds
with the polymers.
11. (canceled)
12. The method of claim 8, wherein the gel comprises a chromium
cross-linked polyacrylamide which is partially based on hydrolyzed
polyacrylamide polymers cross-linked with Cr (III).
13. The method of claim 8, wherein the gel comprises a synthetic
layered silicate clay.
14. The method of claim 8, wherein the gel comprises a thermoset
synthetic gel comprising at least one of a RTV silicone gel or a
perfluorether silicone gel.
15. (canceled)
16. (canceled)
17. The method of claim 8, wherein the stream of gel comprises a
plurality of solid particles of different sizes.
18. (canceled)
Description
[0001] The present invention relates to a method of sealing an
annular space formed between an expandable tubular element arranged
in a wellbore and a wall surrounding the expandable tubular
element, whereby a pressure difference occurs between a first
location in the annular space and a second location in the annular
space axially spaced from the first location.
[0002] Wellbores for the production of hydrocarbon fluid are
conventionally provided with one or more casings to provide
stability to the wellbore wall, and to provide zonal isolation
between different earth formation layers. Generally several casings
are set at different depth, in a nested arrangement whereby the
diameter of each (subsequent) casing is smaller than the diameter
of the previous casing in order to allow lowering of the casing
through the previous casing. The annular space between each casing
and the wellbore wall is filled with cement to provide annular
sealing and to support the casing in the wellbore. In most
applications such cement layer provides adequate sealing
functionality as long as the annular space is not too narrow.
[0003] Recently it has become practice to radially expand casings
in the wellbore. In an attractive method of installing expandable
casings, each subsequent casing is lowered through the previous
casing and then radially expanded to substantially the same
diameter as the previous casing. In this manner a wellbore of
substantially uniform diameter is obtained. Such procedure is
particularly advantageous for relatively deep wellbores or for
extended reach wellbores. Furthermore, it has been proposed to
expand casings against the wellbore wall such that a seal is
created between the casing and the wellbore wall without a cement
layer inbetween. Although such expansion against the earth
formation is considered feasible, there may still be concerns
regarding the effectiveness of the seal after the casing has been
expanded against the formation. Experience has indicated that
cement may not be a good solution for sealing a very narrow annulus
in view of the possibility that the cement does not adequately flow
into the annular space, and in view of possible shrinkage of the
(narrow) annular cement layer upon hardening.
[0004] It is therefore an object of the invention to provide an
improved method of sealing an annular space formed between an
expandable tubular element arranged in a wellbore and a wall
surrounding the expandable tubular element, which overcomes the
drawbacks of the prior art.
[0005] In accordance with the invention there is provided a method
of sealing an annular space formed between an expandable tubular
element arranged in a wellbore and a wall surrounding the
expandable tubular element, whereby a pressure difference occurs
between a first location in the annular space and a second location
in the annular space axially spaced from the first location, the
method comprising: [0006] installing the tubular element in the
wellbore; [0007] locating a body of fluid in the annular space
between said first and second locations, said fluid having a yield
strength selected such that said pressure difference is
insufficient to induce axial flow of the body of non-hardening
fluid in the annular space after radial expansion of the tubular
element; and [0008] radially expanding the tubular element.
[0009] It is thereby achieved that the fluid can be inserted in the
annular space at a relatively low pumping pressure prior to
expansion of the tubular element, since the annular space is
relatively wide before the expansion process. Once the fluid is in
the annular space and the tubular element has been expanded, the
pressure required to induce longitudinal movement of the body of
fluid through the annular space, and thus the sealing capacity of
the annular body of fluid, increases. Such increase is almost
exponential if the annular space becomes very narrow such as in
case the tubular element is expanded (almost) against the wellbore
wall. It will therefore be understood that the method of the
invention is particularly advantageous for applications whereby the
tubular element is radially expanded to near the wellbore wall, or
even locally against the wellbore wall.
[0010] Preferably said fluid is a non-hardening fluid, so that any
risk of shrinkage of the annular body due to hardening is
avoided.
[0011] A suitable fluid for use in the method of the invention is a
thixotropic fluid. Preferably the fluid is selected from a gel, a
Bingham Plastic and a Herschel Bulkley fluid.
[0012] Examples of suitable gels for use in the method of the
invention are: [0013] 1) Chromium cross-linked Polyacrylamide such
as Maraseal.TM., Marcit.TM. available from Schlumberger or OFPG.
These gels are based on partially hydrolyzed polyacrylamide
polymers crosslinked with Cr(III) released via a chrome acetate
complex. Upper application temperatures are 124.degree. C. for
Maraseal, and 104.degree. C. for Marcit. After setting, the gel is
able to resist high concentrations of divalent ions. [0014] 2)
Polyvinyl alcohol cross linked with a special (photosynthesized)
agent, such as disclosed by Advanced Gel Technology Inc. in US
2002/0128374A1, and named Wondergel.TM.. For a more extensive
description of Wondergel.TM. reference is made to WO 03/083259, WO
04/041872, WO 98/12239, US 2004/0072946A1, US 2002/0128374A1 or GB
2396 617A1. [0015] 3) Synthetic layered Silicate clay gels such as
LAPONITE.TM.. [0016] 4) Thixotropic, oleophilic based clay packer
gels for steam injectors such as disclosed in U.S. Pat. No.
5,677,267. [0017] 5) Oil based, thermal insulating gels such as
disclosed in U.S. Pat. No. 4,258,791 or U.S. Pat. No. 5,607,901
which are environmentally safe, non aqueous, non corrosive and
thermally insulating gels, wherein the liquid part includes an
ester of animal or vegetable oil. [0018] 6) In situ gelleable
compositions, normally used in the shut-off of steam injectors, for
example as disclosed in U.S. Pat. No. 4,858,134. [0019] 7)
Thermoset synthetic gels having a long lifetime at elevated
temperature conditions, for example RTV Silicone gels such as Dow
Corning's Sylgard.TM. and/or perfluorether silicone gels such as
Shin Etsu's SIFEL.TM.. [0020] 8) Modified Xantham gums or HPG's for
temperatures below 60.degree. C. [0021] 9) SilJel.TM., composed of
inorganic silicates which solidify in solution to form a permanent
gel after a pre-determined set time. The solution has a viscosity
close to that of water until more than 90% of the set-time has
elapsed. The set-time is temperature- and pH dependent, and varies
between a few minutes and a few hours at temperatures up to
93.degree. C., depending on the pH. The addition of urea at higher
temperatures results in a delayed gelling time due to the buffering
capacity of the urea through the formation of ammonia. [0022] 10)
Injectrol.TM., which is an internally catalyzed silicate system.
Three types of Injectrol.TM. systems are available dependent on the
catalyst applied, i.e. type G for temperatures between
23-66.degree. C., type IT for temperatures between 49-82.degree.
C., and type U for temperatures between 82-149.degree. C. The
internal catalyst system enables pumping of a low viscosity
solution (typically 1.2 mPas) into the formation before the
material sets to a stiff gel. The amount of catalyst and the bottom
hole temperature determines the gelling time. For the type G
system, the gelling time is between a few minutes at 66.degree. C.
and 600 minutes at 23.degree. C. [0023] 11) H2zeroLT.TM. or
H2zero.TM. developed by Halliburton, includes an acrylamide
acrylate co-polymer having a molecular weight of 250.000, with
polyethyleneimine as cross-linker. For applications at temperatures
below 50.degree. C., ZrOCl.sub.2 is used as cross-linker to achieve
reduced gelling times. [0024] 12) PermSeal E+.TM. or PermSeal
600.TM., developed by Halliburton, includes an acrylate monomer and
a thermally controlled activator. KCl, water and a pH adjuster
(acetic acid) are included to provide a standardized ionic
concentration. Thermal degradation of the activator induces in-situ
polymerization of the polymer. Gelling times can be controlled to
be between 1 and 20 hours at temperatures from 21 to 65.degree. C.
PermSeal initially has the same viscosity as water, and forms a
polymer after being pumped into the wellbore. [0025] 13) Floperm
700.TM., developed by Halliburton, includes polyacrylamide and
phenol and formaldehyde as cross-linkers. Precursors which form
phenol and formaldehyde in-situ by degradation reactions, such as
hydroquinone and hexamethylenetetramine, are less toxic. Floperm
700.TM. can be used at temperatures up to about 175.degree. C. The
polymer concentration is of the order of 3000-7000. [0026] 14)
HE300.TM., developed by Halliburton, includes three monomers
(acrylamide-based copolymers). This polymer is recommended for
temperatures beyond 100.degree. C. Crosslinking is possible with
organic components, such as a mixture of phenol and formaldehyde or
precursors to phenol and formaldehyde. Resorcinol can be used to
accelerate the reaction at lower temperatures, while ferric ions
can delay the gelling process.
[0027] In order to enhance the sealing and/or plugging properties
of the body of gel in the annular space, suitably the body of gel
comprises a plurality of solid particles of large particle size
distribution.
[0028] Suitable solid particles to be included in the body of
fluid, are: [0029] malleable particles such as walnut hulls, fibres
(organic or inorganic such as Nylon or Poly-ethylene), hollow
ceramic spheres, wood cuttings, and saw dust; [0030] high density
particles such as Mn3O4 (Micromax.TM.), Barite, Ilmenite,
Haematite, Magnetite, Ferrosilicon, Specularite, Ferrophosphorous,
Silica flour, Silica sand, Bauxite particles, Aluminium micro balls
and micro steel balls; [0031] low density particles such as fly
ash, low density spheres (e.g. Carboprop.TM.), Bentonite,
Pozzolanes, expanded Perlite, powdered coal, Gilsonite.TM., glas
and ceramic micro spheres; [0032] poorly sorted particle systems
such as Dense Crete.TM., Lite Crete.TM., Sandaband.TM. and
Silverfox.TM..
[0033] The invention will be described hereinafter by way of
example in more detail, with reference to the accompanying drawings
in which:
[0034] FIG. 1 schematically shows a wellbore provided with an
expandable casing and a stream of gel being pumped into the
wellbore;
[0035] FIG. 2 schematically shows the wellbore of FIG. 1 after
pumping of the stream of gel into the wellbore;
[0036] FIG. 3 schematically shows the wellbore of FIG. 1 during
radial expansion of the expandable casing;
[0037] FIG. 4 schematically shows the wellbore of FIG. 1 after
radial expansion of the expandable casing; and
[0038] FIG. 5 schematically shows a diagram indicating the effect
of radial expansion of a tubular element in a wellbore on the
sealing functionality of a body of gel in the annular space between
the tubular element and the wellbore wall.
[0039] In the drawings, like reference numerals relate to like
components.
[0040] Referring to FIG. 1 there is shown a wellbore 1 formed in an
earth formation 2 which includes a reservoir layer 3 containing
hydrocarbon fluid, and an overburden layer 4 overlaying the
reservoir layer 3. The wellbore 1 passes through the overburden
layer 4 and extends into the reservoir layer 3. An expandable
tubular element in the form of casing 6 extends from surface into
the wellbore 1 such that the lower end of the casing 6 is arranged
a short distance above the bottom 8 of the wellbore 1. An annular
space 7 is formed between the casing 6 and the wellbore wall. A
stream of gel 10 is pumped through the casing 6 and into the lower
portion of the wellbore 1 using a pump plug 12 located in the
casing 6. The pump plug 12 separates the stream of gel 10 from a
suitable pumping fluid (such as brine) trailing the stream of gel
10 and the pump plug 12. The gel has a yield strength selected in
accordance with selection criteria discussed hereinafter.
[0041] Referring to FIG. 2 there is shown the wellbore 1 after the
stream of gel 10 has been fully pumped into the wellbore 1, whereby
the pump plug 12 is located at the lower end of the casing 6. The
gel 10 extends into the annular space 7 thereby forming an annular
body of gel 11.
[0042] Referring to FIG. 3 there is shown the casing 6 during
radial expansion thereof using an expansion cone 14 connected to a
pump (not shown) at surface by a pipe string 16. The expansion cone
14 is operable between a collapsed state in which the cone 14 has a
largest diameter smaller than the inner diameter of the unexpanded
casing 6, and an expanded state in which the cone 14 has a largest
diameter commensurate with the inner diameter to which the casing 6
is to be expanded. Further, the expansion cone is provided with a
longitudinal through-passage 18 providing fluid communication
between the interior of the casing 6 below the expansion cone 14,
and the pipe string 16. A packer 20 is provided at the lower end of
the casing 6. Similarly to the cone 14, the packer 20 is operable
between a collapsed state in which the packer 20 has a largest
diameter smaller than the inner diameter of the unexpanded casing
6, and an expanded state in which the packer 20 has a largest
diameter commensurate with the inner diameter to which the casing 6
is to be expanded.
[0043] Referring to FIG. 4 there is shown the casing 6 after radial
expansion thereof, whereby the expansion cone 14 and the plug 20
are removed from the casing 6, and whereby a production tubing 22
extends from surface through the expanded casing 6, and into the
lower open-hole portion 13 of the wellbore 1. The production tubing
22 is at surface connected to conventional production equipment
(not shown) so as to allow produced hydrocarbon fluid to flow from
the lower open-hole portion 13 of the wellbore 1 to the production
equipment. Further, the production tubing 22 is near its lower end
sealed to the casing 6 by a production packer 24. The portion of
the stream of gel 10 located in the lower open-hole portion 13 of
the wellbore 1 has been removed from the wellbore 1.
[0044] During normal operation the casing 6 is lowered into the
wellbore and suspended in the wellbore 1 from surface at the
required depth. The annular space 7 is filled with brine (not
shown). Subsequently the stream of gel 10 is pumped via the casing
6 into the wellbore 1 by means of the pump plug 12 which trails the
stream of gel 10 in the casing (FIGS. 1 and 2). The stream of gel
10 flows into the annular space 7 thereby gradually displacing the
brine present in the annular space 7.
[0045] Upon arrival of the pump plug 12 at the lower end of the
casing 6, pumping is stopped and the pump plug 12 is removed from
the casing 6 using a suitable retrieve string (not shown). At this
stage the gel 10 fills the open-hole portion 13 of the wellbore 1
and extends into the annular space 7 thereby forming the annular
body of gel 11.
[0046] In a next step the expansion cone 14 and the packer 20 are
brought to their respective collapsed states, and the packer 20 is
removably attached to the lower end of the cone 14. The combined
cone 14 and packer 20 are then lowered through the casing 6 by
means of pipe string 16 until the cone 14 extends below the lower
end of the casing 6, i.e. in the open-hole portion 13 of the
wellbore 1. The cone 14 is then brought to its expanded state and
pulled into the casing 6 using a force multiplier (not shown)
thereby radially expanding a lower end portion of the casing 6.
When the cone 14 and the packer 20 are fully located in the casing
6, the packer 20 is radially expanded so as to be anchored to the
inner surface of the casing 6. After the packer 20 has been set,
the cone 14 is detached from the packer 20 and brine is pumped via
the pipe string 16 and the through-passage 18, into the interior of
the casing 6 between the cone 14 and the packer 20. The cone 14
thereby moves upwardly through the casing 6 and gradually expands
the casing 6 (FIG. 3). As the annular space 7 becomes narrower
during the expansion process, the annular body of gel 11 moves
upwardly. Upward movement of the annular body of gel 11 stops when
the expansion cone 14 arrives at a level where no gel is present
anymore in the annular space 7. In the Figures, such level is
indicated by dotted line A.
[0047] After the casing 6 has been fully expanded, or after
expansion of a desired portion of the casing 6, the cone 14 and the
packer 20 are removed from the casing. The open-hole portion 13 of
the wellbore 1 is then cleaned, and the production tubing 22 and
the production packer 24 are installed in conventional manner.
[0048] When the well is taken in production, hydrocarbon fluid
flows from the reservoir zone 3 into the open-hole section 13 of
the wellbore, and from there into the production tubing 22 to
surface. The annular body of gel 11 seals the annular space 7 and
thereby prevents that hydrocarbon fluid flows along the outside of
the casing 6 in upward direction. In order that the body of gel 11
in the annular space 7 withstands the (high) fluid pressure of the
hydrocarbon fluid entering the wellbore 1, the yield strength of
the gel is selected such that the axial pressure difference across
the body of gel 11 is lower than a minimum axial pressure
difference across the body of gel 11 required to induce movement of
the body of gel 11.
[0049] An example calculation of the minimum axial pressure
difference across the annular body of gel required to induce
movement of the body of gel for a given gel yield strength, is
presented below.
EXAMPLE
[0050] A wellbore is drilled to a depth of 2000 m, with a diameter
of 0.302 m (11.9 inch) in a lower section of the wellbore. The
fluid pressure in the earth formation at the depth of 2000 m is 200
bar. An expandable casing is installed in the wellbore such that
the lower end of the casing is positioned a short distance above
the wellbore bottom. The outer diameter of the casing in unexpanded
state is 0.244 m (9.625 inch). A stream of gel having a yield
strength of 1000 Pa (0.01 bar), is pumped into the wellbore in the
manner described above such that an annular body of gel of 2.28 m3
is contained in the annular space between the unexpanded casing and
the wellbore wall. The length of the annular body of gel, before
radial expansion of the casing, is 92.08 m. The maximum pressure at
the lower end of the casing required to pump the gel in the annular
space, is 63.74 bar which is well below the fracture pressure of
the surrounding rock formation. The casing is then radially
expanded to an outer diameter of 0.286 m (11.261 inch). The annular
space thereby becomes narrower so that the length of the body of
gel in the annular space increases to about 304.8 m (1000 ft). The
effect of expansion of the casing on the minimum axial pressure
required to induce longitudinal movement of the body of gel in the
annular space, is twofold. Firstly the resistance of the body of
gel to axial movement increases due to a longer contact surface
with both the wellbore wall and the casing wall, and secondly the
cross-sectional area of the annular body of gel decreases. In the
present example it is found that the minimum axial pressure
difference across the body of gel required to induce longitudinal
movement of the body of gel through the annular space, increases
from 211 bar before expansion of the casing, to 751 bar after
expansion of the casing. In the present example, the axial
formation fluid pressure difference across the body of gel is taken
to be solely due to the hydrostatic column of formation fluid along
the length of the body of gel, which is about 30 bar. Thus the
actual axial fluid pressure difference across the body of gel is
far below the minimum axial fluid pressure difference required to
induce longitudinal movement of the body of gel. Therefore in the
present example a gel with a lower yield strength could safely be
applied if desired or, alternatively, the length of the body of gel
in the annular space could be reduced.
[0051] Reference is further made to FIG. 5 showing a diagram
illustrating the minimum axial pressure difference Pa (bar)
required across an annular body of gel having a length of 10 m, to
induce longitudinal movement of the body of gel through an annular
space of width T (mm) for different magnitudes of the yield
strength of the gel whereby: [0052] line (a) indicates a gel yield
strength of 50 Pa; [0053] line (b) indicates a gel yield strength
of 100 Pa; [0054] line (c) indicates a gel yield strength of 200
Pa; [0055] line (d) indicates a gel yield strength of 400 Pa;
[0056] line (e) indicates a gel yield strength of 800 Pa; [0057]
line (f) indicates a gel yield strength of 1600 Pa. As apparent
from the diagram, the magnitude of Pa increases exponentially for T
decreasing to near zero. The effect of radial expansion of the
tubular element is therefore that a gel of relatively low yield
strength can be used, or alternatively a relatively short annular
body of gel can be used, to achieve an effective seal in the
annular space. The sealing functionality of the gel is particularly
effective if the tubular element is radially expanded to near the
wellbore wall, or even locally against the wellbore wall.
[0058] Instead of pumping a gel into the wellbore, a fluid can be
pumped which transforms into a gel some time after being pumped
into the wellbore. Thus, such fluid obtains the desired yield
strength and, optionally, the desired thixotropic properties after
being inserted in the wellbore.
* * * * *