U.S. patent application number 12/665167 was filed with the patent office on 2010-12-16 for swellable apparatus and method of forming.
This patent application is currently assigned to Swelltec Limited. Invention is credited to Brian Nutley, Kim Nutley.
Application Number | 20100314134 12/665167 |
Document ID | / |
Family ID | 38352616 |
Filed Date | 2010-12-16 |
United States Patent
Application |
20100314134 |
Kind Code |
A1 |
Nutley; Kim ; et
al. |
December 16, 2010 |
Swellable Apparatus and Method of Forming
Abstract
A swellable apparatus for filling a space in oil or gas
apparatus and method of forming an apparatus is described. The
apparatus comprises a hydrocarbon swellable body formed from an
elastomeric material selected to expand on exposure to a
hydrocarbon fluid such as EPDM. The swellable body has a first
surface which is exposed to a hydrocarbon fluid, a first (inner)
portion, and a second portion disposed between the first portion
and the surface. The first portion comprises a fluid permeability
structure which differs from the fluid permeability structure of
the second portion. In one embodiment, the cross-linking density of
an outer portion of the body is greater than the cross-linking
density of an inner portion of the body.
Inventors: |
Nutley; Kim; (Inverurie,
GB) ; Nutley; Brian; (Grandholm Village, GB) |
Correspondence
Address: |
(Weatherford) Wong Cabello Lutsch Rutherford &Brucculeri LLP
20333 Tomball Parkway, 6th floor
Houston
TX
77070
US
|
Assignee: |
Swelltec Limited
Dyce, ABERDEEN
GB
|
Family ID: |
38352616 |
Appl. No.: |
12/665167 |
Filed: |
June 23, 2008 |
PCT Filed: |
June 23, 2008 |
PCT NO: |
PCT/GB2008/002159 |
371 Date: |
April 28, 2010 |
Current U.S.
Class: |
166/387 ;
166/131 |
Current CPC
Class: |
C08L 23/18 20130101;
E21B 33/1208 20130101; C08L 2666/06 20130101; C08L 23/16 20130101;
C08L 23/16 20130101 |
Class at
Publication: |
166/387 ;
166/131 |
International
Class: |
E21B 33/12 20060101
E21B033/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2007 |
GB |
0711979.5 |
Claims
1-29. (canceled)
30. A swellable apparatus for filling a space in an oil or gas
apparatus, the swellable apparatus comprising: a unitary
hydrocarbon swellable body formed from an elastomeric material
selected to expand on exposure to a hydrocarbon fluid, the
hydrocarbon swellable body having a first surface which is exposed
to a hydrocarbon fluid during operation, a first portion, and a
second portion disposed between the first portion and the first
surface, wherein the first portion comprises a fluid permeability
structure which differs from a fluid permeability structure of the
second portion.
31. The apparatus as claimed in claim 30, wherein the cross-linking
density of the elastomeric material in the first portion of the
hydrocarbon swellable body differs from the cross-linking density
of the elastomeric material in the second portion of the
hydrocarbon swellable body.
32. The apparatus as claimed in claim 31, wherein the cross-linking
density of the elastomeric material in the second portion is
greater than the cross-linking density of the elastomeric material
in the first portion.
33. The apparatus as claimed in claim 31, wherein the hydrocarbon
swellable body comprises a second surface, and the extent of
cross-linking in the hydrocarbon swellable body decreases in a
direction from the first surface to the second surface.
34. The apparatus as claimed in claim 30, wherein one of the first
or second portions of the hydrocarbon swellable body comprises an
additive comprising a semi-crystalline rubber.
35. The apparatus as claimed in claim 34, wherein one of the first
or second portions of the hydrocarbon swellable body comprises a
polyoctenamer.
36. The apparatus as claimed in claim 35, wherein the polyoctenamer
comprises between about 5% and about 15% of a volume of the first
or second portion of the hydrocarbon swellable body.
37. The apparatus as claimed in claim 30, wherein one of the first
or second portions of the hydrocarbon swellable body comprises an
additive comprising one or more chemical foaming agents.
38. The apparatus as claimed claim 30, further comprising a
plurality of water swellable bodies embedded in the hydrocarbon
swellable body.
39. The apparatus as claimed in claim 30, wherein the hydrocarbon
swellable body comprises at least one pathway for the passage of
water in a wellbore fluid through the hydrocarbon swellable
body.
40. A method of forming a swellable apparatus for filling a space
in an oil or gas apparatus, the method comprising the steps of:
providing an elastomeric material selected to expand on exposure to
a hydrocarbon fluid; curing the elastomeric material to form a
unitary hydrocarbon swellable body; and treating the elastomeric
material such that a first portion of the hydrocarbon swellable
body comprises a fluid permeability structure which differs from
the fluid permeability structure of a second portion of the
hydrocarbon swellable body.
41. The method as claimed in claim 40, comprising the additional
steps of: providing a sheet of hydrocarbon swellable material; and
forming a substantially cylindrical mantle from the sheet of
hydrocarbon swellable material.
42. The method as claimed in claim 41, comprising the additional
step of forming multiple layers of the hydrocarbon swellable
material on a mandrel or tubular.
43. The method as claimed in claim 41, comprising the additional
step of wrapping a sheet of hydrocarbon swellable material onto a
mandrel or tubular.
44. The method as claimed in claim 40, comprising the additional
step of incorporating an additive into the elastomeric material,
the additive comprising a chemical foaming agent.
45. The method as claimed in claim 40, comprising the additional
step of incorporating an additive into the elastomeric material,
the additive comprising a semi-crystalline rubber.
46. The method as claimed in claim 40, comprising the additional
step of treating the hydrocarbon swellable material such that a
second portion of the hydrocarbon swellable body has a higher
extent of cross-linking than a first portion of the hydrocarbon
swellable body.
47. The method as claimed in claim 46, comprising the additional
step of applying a cross-linking agent selectively to parts of the
hydrocarbon swellable body.
48. The method as claimed in claim 47, comprising the additional
steps of: forming multiple layers of the hydrocarbon swellable
material on a mandrel or tubular; and applying a cross-linking
agent to the surface of one or more layers prior to curing the
elastomeric material.
49. A swellable apparatus for filling a space in an oil or gas
apparatus, the swellable apparatus comprising: a hydrocarbon
swellable body formed from a cross-linked elastomeric material
selected to expand on exposure to a hydrocarbon fluid, the
hydrocarbon swellable body having a first surface which is exposed
to a hydrocarbon fluid during operation, wherein the cross-linking
density of the elastomeric material varies in the hydrocarbon
swellable body.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a National Stage entry from PCT
Patent Application No. PCT/GB2008/002159, filed Jun. 23, 2008,
which claims priority to United Kingdom Patent Application No.
GB0711979.5, filed on Jun. 21, 2007, the contents of each one
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a swellable apparatus for
filling a space in oil or gas apparatus and a method of forming
such a swellable apparatus.
BACKGROUND
[0003] Well packers are used to create seals in downhole
environments. Typically, a well packer is used to form a seal in
the annular space between a casing and a tubular located in the
casing or between a drilled hole and a tubular located in the
drilled hole. Instead of mechanical or inflatable well packers, it
is known to form well packers from a material that swells upon
contact with hydrocarbons present in the downhole environment.
[0004] The material is selected to expand on exposure to at least
one predetermined fluid, which may be a hydrocarbon fluid or an
aqueous fluid. The packer may be run to a downhole location in its
unexpanded state, where it is exposed to a wellbore fluid and
caused to expand. The design, dimensions, and swelling
characteristics are selected such that the swellable mantle expands
to create a fluid seal in the annulus, thereby isolating one
wellbore section from another. Swellable packers have several
advantages over conventional packers, including passive actuation,
simplicity of construction, and robustness in long term isolation
applications. Examples of swellable packers and suitable materials
are described in GB 2411918.
[0005] Typically a packer will be constructed for a specific
application and incorporated into a casing string or other tool
string by means of threaded couplings. Swellable packers are
typically constructed from multiple layers of uncured elastomeric
material, such as ethylene propylene diene monomer (EPDM) rubber.
Multiple layers are overlaid on a mandrel or tubular in an uncured
form to build up a mantle of the required dimensions. The mantle is
subsequently cured, e.g. by heat curing or air curing. The outer
surface of the swellable mantle is then machined using a lathe to
create a smooth cylindrical surface. This method produces a fully
cured, unitary swellable mantle capable of sealing large
differential pressures.
[0006] It is important to control the swell rate of the swellable
material of the packer. Swellable materials used to form the
expanding portion of the packer will begin to swell as soon as they
are exposed to triggering fluids. Thus the packers may begin to
expand as they contact drilling oil wellbore fluids during run-in
to their desired location in the wellbore. However, it is desirable
for the packer outer diameter (OD) to be small during run-in to
avoid contact with obstructions, for example washout zones. When
the packer is in its desired location, it is advantageous for the
packer to swell to its fully swelled condition providing a seal in
the wellbore in a short time. It is therefore advantageous to have
a swelling rate profile which takes account of the run-in time of
the packer and the possible exposure of the packer to triggering
fluid during run in. In particular, it may be desirable to impede
or retard the swelling of the packer during an early stage of
exposure to a triggering fluid, but increase the rate of during a
later stage of exposure.
[0007] EP 1315883 discloses a packer system comprising a core of a
first elastomer, and an external elastomer which consists of a
material having a lower diffusion rate of hydrocarbons compared
with the elastomer which constitutes the core.
[0008] In certain applications it is desirable to have a well
packer that swells on exposure to hydrocarbons and water. Such well
packers comprise material that is capable of swelling upon contact
with hydrocarbons and material that is capable of swelling upon
contact with water or brine. Such materials may be referred to as
"hybrid" swelling materials. A well packer that swells upon contact
with both hydrocarbons and water may provide a proper seal during
both the initial and the subsequent stages of production. More
specifically, during an early stage of production the production
fluid may be comprised essentially of hydrocarbons and during later
stages of production the water content of the production fluid may
increase.
[0009] WO 05/012686 discloses a swellable material for downhole
applications comprising an elastomeric matrix material to which has
been added super absorbent polymer (SAP) particles. Such SAP
particles can be classified into starch systems, cellulose systems
and synthetic resin systems. The SAPs have hydrophilic
characteristics by virtue of the presence of alcohols, carboxylic
acids, amides or sulphuric acids. Cross-linking between the
particles creates a three dimensional network. A compound is mixed
with and bound to the material to maintain the desired diffusion
gradient and allow for continued absorption of water (and thus
continued swelling) in aqueous conditions.
[0010] US 2007/0027245 discloses oilfield elements and assemblies
comprising elastomeric compositions capable of swelling in oil and
water. The compositions comprise the reaction product of linear or
branched polymers having residual ethylenic unsaturation with an
unsaturated organic monomer having at least one acidic reactive
moiety.
[0011] One object of the invention is to provide an alternative
swellable apparatus which facilitates control or selection of
swelling characteristics such as swelling rate during exposure to
wellbore fluids.
[0012] The present inventor has appreciated certain shortcomings of
known well packers formed of material capable of swelling upon
contact with hydrocarbons and water. In particular, swelling of
hybrid materials may be inadequate or slow in aqueous (water or
brine) conditions.
[0013] One drawback of blending water swellable bodies such as
superabsorbent polymers with elastomers is that the bodies which
are embedded in the elastomer may migrate towards the surface of
the elastomer that is exposed to water. This can cause the
swellable material to have non uniform swelling. In some cases,
blisters may develop on the surface of the elastomer that is
exposed to water. If these blisters burst open, they will leave
cracks or openings in the elastomer.
SUMMARY
[0014] It is therefore an object of the present invention to
provide a swellable apparatus configured to fill a space in oil or
gas apparatus that addresses such shortcomings.
[0015] It is a further object for the present invention to provide
a method of forming swellable apparatus for filling a space in oil
or gas apparatus.
[0016] According to a first aspect of the invention, there is
provided a swellable apparatus for filling a space in oil or gas
apparatus, the swellable apparatus comprising a unitary hydrocarbon
swellable body formed from an elastomeric material selected to
expand on exposure to a hydrocarbon fluid, the hydrocarbon
swellable body having an first surface which, in use, is exposed to
a hydrocarbon fluid, a first portion, and a second portion disposed
between the first portion and the first surface, wherein the first
portion comprises a fluid permeability structure which differs from
the fluid permeability structure of the second portion.
[0017] In this context, the term "unitary" means cured or otherwise
formed into a single body or mass. In this specification,
elastomeric material means a synthetic or natural material
displaying elastomeric or rubber-like characteristics, and includes
compositions comprising polymeric and non-polymeric additives
including stabilisers, fillers, co-agents and others.
[0018] The first surface is preferably an outer surface exposed to
a wellbore fluid, but in an alternative configuration the first
surface is exposed to a triggering fluid, which may be delivered
internally or via a fluid delivery system.
[0019] The permeability of the hydrocarbon swellable body may be
varied by varying the cross-linking density of the elastomeric
material in parts of the hydrocarbon swellable body. The
cross-linking density of the first portion may be less than the
cross-linking density of the second portion. The composition of the
elastomeric material may otherwise be the same in the first and
second portions.
[0020] Thus according to a second aspect of the invention, there is
provided a swellable apparatus for filling a space in oil or gas
apparatus, the swellable apparatus comprising a hydrocarbon
swellable body formed from a cross-linked elastomeric material
selected to expand on exposure to a hydrocarbon fluid, the
hydrocarbon swellable body having a first surface which, in use, is
exposed to a hydrocarbon fluid, wherein the cross-linking density
of the elastomeric material varies in the hydrocarbon swellable
body.
[0021] Embodiments of the second aspect of the invention may
comprise preferred and optional features of the first aspect of the
invention and vice versa.
[0022] Different parts of the hydrocarbon swellable body may
therefore have different cross-linking densities. By varying the
cross-linking density of the material which makes up the body, the
diffusion rate, and thus the swelling rate, of the swellable
apparatus is affected. A higher cross-linking density reduces the
diffusion rate of hydrocarbon fluid when compared with a lower
cross-linking density. The apparatus thus has a permeability
structure which varies in the body. The invention may therefore
provide a unitary body of cured elastomeric material which
facilitates control and/or selection of swelling
characteristics.
[0023] Preferably, the extent of cross-linking in the hydrocarbon
swellable body decreases in an inward direction from the first
surface. The hydrocarbon swellable body may have a first surface
directed towards a hydrocarbon fluid and a second surface, wherein
the extent of cross-linking in the hydrocarbon swellable body
decreases in a direction from the first surface to the second
surface.
[0024] More specifically, an extent of cross-linking at an outer
surface of the hydrocarbon swellable body may be higher than an
extent of cross-linking within the hydrocarbon swellable body, the
outer surface, in use, coming into contact with the first fluid. In
use, a high extent and/or density of cross-linking at the outer
surface may control or retard an uptake of hydrocarbon molecules by
the hydrocarbon swellable body whilst allowing a part of the
hydrocarbon swellable body having a lower extent of cross-linking
to have faster penetration of the hydrocarbon molecules and thus
faster swelling.
[0025] A greater extent of cross-linking at the first surface may
reduce a rate of uptake of hydrocarbon molecules by the hydrocarbon
swellable body. Therefore, an extent of cross-linking at the first
surface may be predetermined to set a predetermined rate of uptake
of hydrocarbon molecules. This has advantages in certain wellbore
environments where it is desirable for swelling of the apparatus to
be retarded, for example during run-in of the apparatus to its
required depth. An elastomer having an increased cross-linking
density may have a reduced tendency to suffer from migration of the
water swellable body towards the surface of the elastomer that is
exposed to water and thus reduce non-uniform swelling.
[0026] More specifically, the extent of cross-linking at the
surface of the hydrocarbon swellable body may be between about 10
and about 100 times higher than at a location in the hydrocarbon
swellable body spaced apart from the first surface of the
hydrocarbon swellable body.
[0027] Alternatively or in addition, the permeability of the
hydrocarbon swellable body may be varied by varying the macroscopic
bond structure of the elastomeric material. Thus different parts of
the body may have different macroscopic bond structures. This may
be achieved by incorporating in a part of the swellable body of a
polymer additive or a plurality of specific polymer additives,
which may comprise a semi-crystalline rubber and/or polyoctenamer
such as VESTENAMER.RTM..
[0028] The preferred additive is VESTENAMER.RTM., but the additive
may comprise one or more rubbers as described in
trans-Polyoctenamer by Draxler, Marl A. & Kautschuk, Gummi,
Kunststoffe, 34, Nr. 3/1981, pp. 185-190; and 25 Jahre
Polyoctenamer-der Entwicklungsgang eines Synthesekautschuks vom
Laborpraparat zum industriellen Rohstoff, by Draxler, Marl A.,
Kautschuk, Gummi Kunststoffe, 42, Nr. 10/1989, pp. 868-874,
incorporated herein by reference.
[0029] Thus the inner portion of the swellable body may incorporate
a semi-crystalline rubber or polyoctenamer to provide a macroscopic
bond structure, whereas an outer portion of the swellable body
disposed towards the outer surface of the body may not have a
semi-crystalline rubber or polyoctenamer incorporated therein.
[0030] It is believed that the addition of a semi-crystalline
rubber polyoctenamer results in a macroscopic bond structure which
increases the permeability of the apparatus to increase the access
of the water to the water swellable bodies. Thus access pathways
are provided by the macroscopic bond structure of the material. The
macroscopic bond structure also improves the retention of the water
swellable body in the hydrocarbon swellable body.
[0031] More specifically, the polymer additive, such as
VESTENAMER.RTM., may comprise between about 5% and about 15% of a
volume of the swellable apparatus.
[0032] In an alternative embodiment of the invention, the swellable
apparatus comprises one or more foaming agents or blowing agents. A
chemical foaming agent decomposes to release a gas when heated to
its activation temperature. A range of different chemical foaming
agents may be used with the invention. One example is a
dinitrosopentamethylene tetraamine (DNPT) such as OPEX.RTM. 80,
available from Uniroyal Chemical. Another suitable additive is
based on the family of azodicarbonamide type chemicals, for
example, those provided by Lanxess Group under the POROFOR.RTM.
brand.
[0033] The foaming agent may be incorporated into the swellable
apparatus during mixing, and subsequently treated, for example by
heating to decompose and impart a cellular structure to the EPDM
matrix material. Preferably, the cellular structure is an open
cellular structure. Thus the cellular structure may provide one or
more fluid pathways within the hydrocarbon swellable body, which
increases the permeability of the swellable apparatus.
[0034] The swellable apparatus may comprise a plurality of water
swellable bodies. The plurality of water swellable bodies may, for
example, be embedded in the hydrocarbon swellable body such that
the water swellable bodies are spaced apart from each other. The
water swellable bodies may be evenly and uniformly spaced apart
from each other.
[0035] Alternatively or in addition, the hydrocarbon swellable body
may comprise at least one pathway therethrough. Thus, the at least
one pathway may provide for the passage of water comprised in the
second fluid through the hydrocarbon swellable body. The provision
of at least one pathway may provide for ease of access of water to
the water swellable body, e.g. compared with known swellable
apparatus.
[0036] The at least one pathway may be configured to permit the
passage of water molecules but prevent the passage of hydrocarbon
molecules contained in the first fluid. This limits or eliminates
the effect that providing pathways in the apparatus has on the
hydrocarbon-swelling characteristics of the apparatus.
[0037] Thus, the at least one pathway may allow for the passage of
water molecules. Alternatively or in addition, the at least one
pathway may have a diameter of less than about 1000 microns. Thus,
the at least one pathway may prevent the passage of the at least
one water swellable body, when the at least one water swellable
body is embedded in the hydrocarbon swellable body.
[0038] More specifically, the at least one pathway may have a
diameter of less than about 100 microns, and may preferably be
about 40 microns. Such a dimension means that hydrocarbon molecules
may not readily pass through the pathway.
[0039] Alternatively or in addition, the swellable apparatus may be
configured such that the at least one pathway may extend from an
outer surface of the hydrocarbon swellable body through the
hydrocarbon swellable body to the at least one water swellable
body, the outer surface, in use, coming into contact with the first
and second fluids.
[0040] Alternatively or in addition, the pathway may comprise a
bore. The bore may, for example, be formed by perforation of the
hydrocarbon swellable body. The perforation may be a mechanical
perforation, and may be formed by penetrating the hydrocarbon
swellable body with a pin, needle or spike, or may be a perforation
formed by a laser, for example in a micro-drilling process.
[0041] Alternatively or in addition, the pathway may comprise a
macroscopic bond structure between the hydrocarbon swellable body
and the at least one water swellable body. Such a macroscopic bond
structure may, for example, be formed by the inclusion of a polymer
material, which may be a semi-crystalline rubber and/or
polyoctenamer such as VESTENAMER.RTM..
[0042] More specifically, the polymer material, such as
VESTENAMER.RTM., may comprise between about 5% and about 15% of a
volume of the swellable apparatus.
[0043] Changing at least one of a number of pathways and a density
of pathways per unit area of the outer surface of the hydrocarbon
swellable body may provide for control of access of water molecules
to the at least one water swellable body. Thus, at least one of the
number of pathways and the pathway density may be increased to
increase access of a selected fluid to the at least one swellable
body. Hence, changing at least one of the number of pathways and
the pathway density may control an uptake of an aqueous fluid by
the water swellable body whilst not affecting an uptake of a
hydrocarbon fluid by the hydrocarbon swellable body.
[0044] Alternatively or in addition, the hydrocarbon swellable body
may comprise a polymer. Alternatively or in addition, the
hydrocarbon swellable body may comprise an elastomer.
[0045] Alternatively or in addition, the hydrocarbon swellable body
may comprise ethylene propylene diene monomer rubber (EPDM).
Alternatively or in addition, the hydrocarbon swellable body may be
operative to swell upon contact with the first fluid by diffusion
of hydrocarbon molecules into the hydrocarbon swellable body.
Alternatively or in addition, the water swellable body may comprise
a polymer.
[0046] More specifically, the water swellable body may comprise a
Super Absorbent Polymer (SAP), which may be an acrylic acid and
sodium acrylate copolymer such as AQUALIC.RTM.. Alternatively or in
addition, the water swellable body may comprise a salt, such as
NaCl or CaCl2. Alternatively or in addition, the water swellable
body may be operative to swell upon contact with water by means of
diffusion of water molecules into the water swellable body. More
specifically, where the water swellable body comprises a salt, the
water swellable body may be operative to swell upon contact with
water by means of osmosis.
[0047] Alternatively or in addition, the hydrocarbon swellable body
may comprise between about 35% and about 50% of a volume of the
swellable apparatus and the water swellable body may comprise
between about 15% and about 40% of the volume of the swellable
apparatus. In use, such a composition may provide for an increase
in volume for the swellable apparatus from the unswollen condition
to the swollen condition of up to about 300% an environment such as
that found in a downhole oil well. For example, within 2-3 weeks of
exposure to a 100 degree Celsius fluid mixture containing both a
hydrocarbon-based liquid and low salinity aqueous solution.
[0048] More specifically, the hydrocarbon swellable body may
comprise between about 40% and about 45% of the volume of the
swellable apparatus.
[0049] Alternatively or in addition, the water swellable body may
comprise between about 25% and about 35% of the volume of the
swellable apparatus.
[0050] Alternatively or in addition, the swellable apparatus may
comprise a filler, such as carbon black or silica oxide. More
specifically, the filler may comprise between about 15% and about
30% of a volume of the swellable apparatus.
[0051] Alternatively or in addition, the swellable apparatus may
comprise an activator, which is operative to form a sulphurating
compound. More specifically, the activator may comprise at least
one of zinc oxide and stearic acid. When zinc oxide and stearic
acid are present a zinc sulphurating compound may be formed. More
specifically, the stearic acid may comprise less than about 2% of a
volume of the swellable apparatus.
[0052] Alternatively or in addition, the swellable apparatus may
comprise a metal oxide, such as zinc oxide. In the curing process
the zinc oxide may activate an organic accelerator. Suitable
organic accelerators include zinc diacrylate (ZDA), zinc
dimethacrylate (ZDMA), triallyl cyanate (TAC), or
triallylisocyanate (TAIC.RTM.), including those available from
Sartomer Company, Inc of Pennsylvania, USA. An unreacted portion of
the zinc oxide may remain available to neutralize sulphur-bearing
acidic decomposition products formed during vulcanization. Adequate
levels of zinc oxide can contribute markedly to chemical
reinforcement, scorch control and resistance to heat-aging and
compression fatigue.
[0053] More specifically, the metal oxide may comprise less than
about 5% of a volume of the swellable apparatus.
[0054] Alternatively or in addition, at least one of the first
fluid and the second fluid may be comprised in a downhole fluid
present in a downhole environment. More specifically, the downhole
fluid may comprise at least one of: a completion brine; a
water-based drilling mud; an oil-based drilling mud; formation
water; and a production fluid, e.g. oil or gas from a well being
produced.
[0055] Thus, the swellable apparatus may be used, e.g. in a well
packer, where it may be activated by water based completion fluids.
After a completion operation and during a well production phase,
the swellable apparatus may be used to form a seal, even though the
swellable may then be mainly exposed to hydrocarbons.
[0056] Alternatively or in addition, the swellable apparatus may be
operative to increase in volume from an unswollen condition to a
swollen condition by up to about 300% when in contact with at least
one of the first fluid and the second fluid. Thus, the swellable
apparatus may be operative to swell based on simultaneous swelling
of both the hydrocarbon swellable body and the water swellable
body.
[0057] According to a third aspect of the invention, there is
provided a swellable material for filling a space in oil or gas
apparatus, the swellable material selected to swell on exposure to
a wellbore fluid, wherein the swellable material comprises an
elastomeric material and an additive comprising a semi-crystalline
rubber and/or a polyoctenamer.
[0058] The preferred additive is VESTENAMER.RTM., but the additive
may comprise one or more rubbers as described in
trans-Polyoctenamer by Draxler, Marl A. & Kautschuk, Gummi,
Kunststoffe, 34, Nr. 3/1981, pp. 185-190; and 25 Jahre
Polyoctenamer-der Entwicklungsgang eines Synthesekautschuks vom
Laborpraparat zum industriellen Rohstoff, by Draxler, Marl A.,
Kautschuk, Gummi Kunststoffe, 42, Nr. 10/1989, pp. 868-874,
incorporated herein by reference.
[0059] Thus the swellable material may incorporate a
semi-crystalline rubber or polyoctenamer to provide a macroscopic
bond structure. It is believed that the addition of a
semi-crystalline rubber and/or a polyoctenamer results in a
macroscopic bond structure which increases the permeability of the
material to increase the access of wellbore fluids into the
swellable material or a body formed therefrom. Thus access pathways
are provided by the macroscopic bond structure of the material. The
macroscopic bond structure also improves the retention of a water
swellable body such as an SAP in a swellable body.
[0060] The elastomeric material may be an ethylene propylene
copolymer such as EPDM.
[0061] More specifically, the polymer additive, such as
VESTENAMER.RTM., may comprise between about 5% and about 15% of a
volume of the swellable apparatus.
[0062] Embodiments of the third aspect of the invention may
comprise preferred and optional features of the first or second
aspects of the invention and vice versa.
[0063] According to a fourth aspect of the invention, there is
provided an oil or gas tool comprising the swellable apparatus of
the first, second or third aspects of the invention. The tool may
be a downhole tool, and may be a wellbore packer, anchor or
centraliser.
[0064] Embodiments of the fourth aspect of the invention may
comprise preferred and optional features of the first to third
aspects of the invention and vice versa.
[0065] According to a fifth aspect of the invention, there is
provided a method of forming a swellable apparatus for filling a
space in oil or gas apparatus, the method comprising the steps of:
providing an elastomeric material selected to expand on exposure to
a hydrocarbon fluid; curing the elastomeric material to form a
unitary hydrocarbon swellable body; treating the elastomeric
material such that a first portion of the hydrocarbon swellable
body comprises a fluid permeability structure which differs from
the fluid permeability structure of a second portion of the
hydrocarbon swellable body.
[0066] The method may include the steps of providing a sheet of
hydrocarbon swellable material, forming a substantially cylindrical
mantle from the sheet of hydrocarbon swellable material. The method
may comprise the steps of forming multiple layers of the
hydrocarbon swellable material on a mandrel or tubular.
[0067] The multiple layers may be formed by wrapping a sheet of
hydrocarbon swellable material onto the mandrel or tubular. A
cross-linking agent may be applied to the surface of one or more
layers. For example, the outermost layers may be coated with a
cross-linking agent. The multiple layers may be of an uncured
elastomeric material.
[0068] Alternatively, or in addition, the method may comprise the
step of incorporating an additive into the elastomeric material.
The additive may be a pathway forming material with the hydrocarbon
swellable material and the water swellable material. Alternatively,
or in addition, the additive may be a chemical foaming agent. The
pathway forming material may comprise a polymer, which may be a
semi-crystalline rubber and/or polyoctenamer such as
VESTENAMER.RTM..
[0069] Alternatively or in addition, the method may comprise
treating the hydrocarbon swellable material such that an outer
surface of the hydrocarbon swellable body has a higher extent of
cross-linking than within the hydrocarbon swellable body. The
elastomeric material may be treated by applying a cross-linking
agent. The cross-linking agent may be selectively applied to parts
of the hydrocarbon swellable body. More specifically, treating the
hydrocarbon swellable material may comprise providing a curing
material on an uncured outer surface of the hydrocarbon swellable
body.
[0070] More specifically, the curing material may comprise at least
one of: a cure accelerator; and a curing agent. Cure accelerators
or curing agents are well and widely known to those skilled in the
art of elastomer or polymer science.
[0071] Alternatively or in addition, providing the curing material
may comprise at least one of spraying and painting at least one
application (e.g. such that it forms a temporary coating to be
absorbed by the swellable material) of the curing material onto the
outer surface of the hydrocarbon swellable member.
[0072] More specifically, the curing material may be provided on
the outer surface before the swellable member is cured. The process
of curing the swellable member will be well known to persons
skilled in the art. More specifically, skilled persons will have a
full understanding of parameters associated with temperatures and
pressures required to cure swellable members formed of an
elastomer; such a process will be familiar to skilled persons as
vulcanisation. It will be appreciated that peroxide curing and/or
sulphur curing may be used with the present invention.
[0073] Alternatively or in addition, the curing material may be
dissolved as an aqueous solution or in a solvent.
[0074] More specifically, the curing material may have a
predetermined concentration when in the form of an aqueous solution
or solvent. Thus, the concentration may be changed from one curing
step to another such that when the curing material is applied to an
outer surface of the hydrocarbon swellable member an extent of
cross-linking may be controlled.
[0075] In one embodiment of the invention a curing material is
provided on the outer surface of a fully or substantially cured
material prior to a re-curing process to change the cross-linking
structure of the material.
[0076] Embodiments of the fifth aspect of the invention may
comprise preferred and optional features of the first to fourth
aspects of the invention and vice versa.
[0077] The present inventor has appreciated the feature of varying
an extent of cross-linking across the hydrocarbon swellable body
has particular application to a hybrid swellable material. Thus,
from a sixth aspect of the present invention there is provided a
swellable apparatus for filling a space in oil or gas apparatus,
the swellable apparatus comprising a hydrocarbon swellable body and
at least one water swellable body,
[0078] the swellable apparatus, in use, being operative to fill the
space in oil or gas apparatus when in a swollen condition, the
swellable apparatus adopting the swollen condition when at least
one of the hydrocarbon swellable body and the at least one water
swellable body are swollen, the hydrocarbon swellable body swelling
upon contact with a first fluid comprising a hydrocarbon; and the
at least one water swellable body swelling upon contact with a
second fluid comprising water, the hydrocarbon swellable body
having a structure that varies as to an extent of cross-linking
across the hydrocarbon swellable body.
[0079] More specifically, an extent of cross-linking at an outer
surface of the hydrocarbon swellable body may be higher than an
extent of cross-linking within the hydrocarbon swellable body, the
outer surface, in use, coming into contact with the first
fluid.
[0080] Alternatively or in addition, the swellable apparatus may be
configured such that the hydrocarbon swellable body is operative to
control access of the second fluid to the at least one water
swellable body.
[0081] Embodiments of the sixth aspect of the invention may
comprise preferred and optional features of the first to fifth
aspects of the invention and vice versa.
[0082] According to a seventh aspect of the present invention,
there is provided a method of forming a swellable apparatus for
filling a space in oil or gas apparatus, the method comprising:
incorporating a hydrocarbon swellable material and a water
swellable material, the hydrocarbon swellable material forming a
hydrocarbon swellable body and the water swellable material forming
at least one water swellable body, the hydrocarbon swellable
material and the water swellable material being incorporated such
that, in use, the formed hydrocarbon swellable body swells upon
contact with a first fluid comprising a hydrocarbon and the at
least one water swellable body swells upon contact with a second
fluid comprising water, and treating the hydrocarbon swellable body
such that an extent of cross-linking of the hydrocarbon swellable
body varies across the hydrocarbon swellable body.
[0083] More specifically, the hydrocarbon swellable body may be
treated such that an outer surface of the hydrocarbon swellable
body has a higher extent of cross-linking than within the
hydrocarbon swellable body.
[0084] Alternatively or in addition, the hydrocarbon swellable
material and the water swellable material may be further
incorporated such that, in use, the hydrocarbon swellable body is
operative to control access of the second fluid to the at least one
water swellable body.
[0085] Embodiments of the seventh aspect of the invention may
comprise preferred and optional features of the sixth aspect of the
invention and vice versa.
[0086] According to an eighth aspect of the invention, there is
provided a method of forming a swellable material for filling a
space in oil or gas apparatus, the swellable material selected to
swell on exposure to a wellbore fluid, the method comprising the
step of combining an elastomeric material and an additive
comprising a semi-crystalline rubber and/or a polyoctenamer.
[0087] The method may comprise the additional step of curing the
combined elastomeric material and additive.
[0088] Embodiments of the eighth aspect of the invention may
comprise preferred and optional features of the third aspect of the
invention and vice versa.
BRIEF DESCRIPTION OF THE DRAWINGS
[0089] There will now be described, by way of example only,
embodiments of the invention with reference to the following
drawings, of which:
[0090] FIG. 1 is a cross-section of a wellbore packer comprising
swellable apparatus in accordance with an embodiment of the
invention;
[0091] FIG. 2 is a longitudinal section of a downhole tool
comprising swellable apparatus in accordance with an embodiment of
the invention;
[0092] FIG. 3 is a schematic line drawing of a material for the
swellable apparatus of FIG. 2;
[0093] FIG. 4 is a schematic view of the swellable apparatus of the
downhole centraliser tool of FIG. 2;
[0094] FIG. 5 is a graph of swelling profile for samples of a
swellable apparatus in accordance with embodiments of the
invention;
[0095] FIG. 6A is a graph of swelling profile for two samples of
swellable material in water;
[0096] FIG. 6B is a graph of swelling profile for two samples of
swellable material in a hydrocarbon fluid; and
[0097] FIG. 7 is a cross-section of a wellbore packer in accordance
with an alternative embodiment of the invention.
DETAILED DESCRIPTION
[0098] Referring firstly to FIG. 1, there is shown in cross section
a wellbore packer which comprises a swellable material in
accordance with an embodiment of the invention. The packer,
generally shown at 10, comprises a swellable mantle 12 disposed on
a tubular 14. The packer is configured to be disposed in a wellbore
such that its outer surface 16 is exposed to wellbore fluids. In
this example, the swellable mantle 12 is formed from an elastomeric
material comprises an ethylene propylene diene monomer (EPDM)
rubber, selected to swell on exposure to a hydrocarbon fluid. The
swellable mantle 12 has a cross-linking density which varies across
its cross section. An inner volume or core 18 comprises a
relatively low density of cross-linking of the elastomeric
material. An outer volume 20, disposed between the outer surface 16
and the inner volume 18, has a relatively high cross-linking
density. The volume 20 has a lower permeability and swell rate to
wellbore fluids by virtue of its increased cross-linked density.
Thus the diffusion of the well fluids into the body is retarded by
the relatively highly cross-linked volume 20.
[0099] The volume 20 of high cross-linking is achieved by coating
the outer surface of the formed swellable mantle with a
cross-linking accelerator such as zinc diacrylate (ZDA). The
cross-linking accelerator is coated on to the outer surface by
spraying or brushing, and allowed to penetrate into the swellable
mantle 12. Subsequently, the swellable mantle may be cured or
re-cured to cause the cross-linking to occur and create a unitary
hydrocarbon swellable body with the relatively high density
cross-linked region 20.
[0100] Although in FIG. 1 the high cross-linked region 20 appears
to have a discrete boundary with the relatively low cross-linked
region 18, in practice there is a region of continuous change in
cross-linking density due to the gradual penetration of the
cross-linking agent into the swellable mantle 12. The relative
thickness of the high cross-linked region 20, and the relative
densities of cross-linking in the volumes can be varied by changing
the amount of cross-linking accelerator applied to the outer
surface, and the time it is allowed to penetrate into the swellable
mantle before the curing or re-curing process is performed.
[0101] FIG. 2 shows generally at 100 a swellable centraliser of an
alternative embodiment of the invention, located downhole in a
subterranean wellbore 112. The centraliser 100 is provided with a
swellable apparatus 116, which can swell in the presence of
hydrocarbon and aqueous wellbore fluids to fill the annular space
118. To achieve this, the swellable apparatus 116 is formed from a
"hybrid" material containing both hydrocarbon and water swellable
bodies, as described in more detail with reference to FIG. 3.
Access to the water and hydrocarbon swellable bodies by
hydrocarbons and water, which will be present in wellbore fluids,
is controlled by the structure of the swellable material.
[0102] The swellable material 120 has a hydrocarbon swellable body
in the form of an ethylene propylene diene monomer rubber (EPDM)
elastomer matrix, together with water swellable bodies 132 in the
form of super absorbent polymers (SAPs) embedded within the matrix
122. The polymer bodies 132 are evenly distributed and spaced apart
from each other throughout the material. Upon being brought into
contact with hydrocarbon molecules, the EPDM matrix is caused to
swell, while the super absorbent polymers swell upon contact with
water. This ensures proper performance of the swellable apparatus
to seal the wellbore annulus 118 around the centraliser tool in the
presence of both water and hydrocarbon based well fluids, and in
the presence of fluids consisting of water and hydrocarbons are
mixed together.
[0103] In this example, hydrocarbon molecules diffuse into the EPDM
matrix and water molecules diffuse into the super absorbent
polymers. The EPDM matrix makes up about 40% of the material
volume, while the super absorbent polymers make up a further 20% of
the volume. This helps to achieve the desired swelling behaviour.
Further, the material volume includes a silica oxide filler, a zinc
oxide and stearic acid.
[0104] Relative quantities of the above mentioned components used
in forming the swellable material of this example are specified in
Table A below:
TABLE-US-00001 TABLE A Component Phr % EPDM (calendering grade) 100
39.2% HAF N330 Carbon Black 48 18.8% Processing Oil 20 7.8% Zinc
Oxide 5 2.0% Peroxide (pure) 5 2.0% Co-agent (TAC or TAIC) 2 0.8%
Stearic Acid 1 0.4% VESTENAMER .RTM. 10 3.9% Water Absorbent Resin
(AQUALIC .RTM.) 64 25.1% TOTAL 255 100.0%
[0105] FIG. 4 provides a more detailed view of the apparatus shown
in FIGS. 2 and 3. The apparatus is formed from the material 120
described with reference to FIG. 3.
[0106] In FIG. 4 the apparatus is additionally shown having a
number of sub-micron pathways 140 through the material 120. The
pathways 140 provide access for water molecules from the wellbore
environment 142 through the surface region 144 of the wellbore
apparatus 100 to the water absorbing polymers. In this example, the
pathways 140 are created by mechanical perforations through the
material 120. The pathways 140 are sized to permit water molecules
to pass readily through the bores. However, hydrocarbon molecules
do not readily pass through the pathways. The density of pathways
140 is selected to provide adequate access of water for the
required swelling properties, such as rate and volume expansion, of
the swellable apparatus 100.
[0107] The perforations are produced in an automated process using
a perforating roller body, such as described in U.S. Pat. No.
3,646,639. In alternative embodiments the perforations may be
formed using a laser or micro-drilling process using a system of
CO2 lasers.
[0108] The swellable hybrid material is vulcanised to produce
cross-linking of the EPDM matrix 122. In this example, the
swellable apparatus has a strongly cross-linked surface region 146,
followed below by a region 148 of intermediate cross-linking, and a
further main region 150 that is cross-linked to a still lesser
degree. The extent of cross-linking controls access of hydrocarbon
molecules to the hydrocarbon swellable matrix 122, such that the
swelling behaviour of the apparatus in the presence of hydrocarbons
can be selected appropriately.
[0109] In this case, the cross-linking at the surface is strong to
retard the uptake of hydrocarbon molecules and the degree and/or
speed of hydrocarbon-activated swelling, while in other regions,
which are cross-linked to a lesser extent, hydrocarbon molecules
that have been taken up are allowed to diffuse more effectively
throughout the material.
[0110] In order to create such a cross-linked structure, a
cross-linking or curing agent such as zinc diacrylate (ZDA) is
coated onto the outer surface by spraying or brushing. The variable
cross-linking profile in this example is substantially continuous,
due to the diffusion of the cross-linking agent into the swellable
body.
[0111] In order to create such a cross-linked structure, a
cross-linking or curing agent such as zinc diacrylate (ZDA) is
deposited onto the outer surface by spraying or brushing. This may
be carried out during the construction of the packer apparatus
before curing to adjust the cross-linking characteristics and, in
turn, the nature of the swelling. The EPDM component of the
material is cross-linked upon curing of the EPDM.
[0112] Samples of the swellable material with the composition
specified in Table A were placed in tap water at a controlled
temperature of 80 degrees Celsius, and the mass changes were
measured over a period of several days. FIG. 5 is a graph of
water-swell profile for samples having a number of different
perforation densities. In each case the perforations were
mechanically formed in the sample using a perforating needle. The
data show that perforating the material has a marked effect on the
swell profile. For example, at around 15 days, the sample with 1050
perforations per square inch (approximately 6.45 square cm) had
increased in mass by around 200%, compared with an increase of
around 75% for the unperforated case. The sample with 132
perforations per square inch (approximately 6.45 square cm) had
increased in mass by around 112%. The data also show the maximum
mass increases to be higher where the perforation density is
higher.
[0113] To measure the effect on the swelling profile in a
hydrocarbon fluid, samples of the same material composition with no
perforations, 16 perforations, 64 perforations and 132 perforations
per square inch (approximately 6.45 square cm) were placed in the
special kerosine Clairsol 350 MHF.TM. at a controlled temperature
of 80 degrees Celsius. The mass increase of the samples was
measured, and the data showed no significant effect on swelling
profile, i.e. the perforations did not significantly affect the
penetration of the hydrocarbon into the body.
[0114] Samples of the material composition specified in Table A
were compared with a similar composition with the VESTENAMER.RTM.
omitted. Samples of each composition were placed in tap water at a
controlled temperature of 80.degree. C. FIG. 6A is a plot of
percentage mass change versus time for the respective samples. The
data show a clear increase in swell profile for the swellable
material containing VESTENAMER.RTM. compared to the swellable
material with no VESTENAMER.RTM..
[0115] Identical samples were placed in Clairsol 350 MHF.TM. at a
controlled temperature of 80.degree. C. to model the effect of the
VESTENAMER.RTM. in a hydrocarbon well fluid environment, with the
measured mass increase plotted in FIG. 6B. The data show an
improved swell rate and improved maximum swell increase for the
swellable material with the VESTENAMER.RTM., compared to the
swellable material without VESTENAMER.RTM..
[0116] It is believed that the addition of the VESTENAMER.RTM.
results in a macroscopic bond structure within the material which
increases the permeability to wellbore fluids. This increases the
access of water contained in a wellbore fluid to the water
swellable bodies in the elastomer. In addition, the macroscopic
bond structure increases the permeability of the apparatus to
hydrocarbon fluids. The data also show that the addition of the
VESTENAMER.RTM. increases the maximum swell increase of the
material. Although the examples shown relate to VESTENAMER.RTM.,
the addition of other semi-crystalline rubbers and/or
polyoctenamers also falls within the scope of the invention. Thus
in particular embodiments, the access pathways providing access for
water molecules to the super absorbing polymer bodies may be formed
by the macroscopic bond structure of the material itself.
[0117] FIG. 7 is a cross sectional view through a packer in
accordance with an alternative embodiment of the invention. The
packer, generally shown at 200, is similar to the packer 10 of FIG.
1, but differs in its construction. The packer comprises an
expanding portion 215 of cylindrical form located on a tubular 214.
The packer is formed by forming multiple wraps 202a, 202b, and 202c
of an elastomeric material 230 on the tubular 214. The elastomeric
material 230 consists of a substantially rectangular sheet. In this
example, the elastomeric material 230 is extruded EPDM and is
uncured. The elastomeric material will typically be formed in a
continuous length of several tens of metres, and may conveniently
be deployed from a storage reel.
[0118] The lowermost layer 202a of the material is secured to the
tubular 214 by a bonding agent, which may be a cyanoacrylate based
adhesive. The multiple layer construction allows treatments to be
applied to different parts of the swellable mantle. In this
embodiment, the outer surfaces of the two outermost layers 202b,
202c of the material are coated with a cross-linking agent such as
ZDA. This may be applied to the material prior to its application
to the tubular over selected areas of the material. Alternatively,
the treatment may be applied to the different layers during
application on to the tubular.
[0119] When the expanding portion is formed it is cured, for
example by a heat curing process, to form a unitary body of
hydrocarbon swellable material. A cross-linking accelerator has
been selectively applied to an outer volume of the expanding
portion, resulting in an inner volume 218 with relatively low
cross-linking density, compared with an outer volume 220 with
relatively high cross-linking density.
[0120] In an alternative embodiment (not illustrated), the
elastomeric material 230 is replaced by a sheet material of a
hybrid swellable material, such as that described with reference to
FIGS. 2 to 4. In a further alternative embodiment, the permeability
structure of the swellable body is affected by creating a
macroscopic bond structure. This is achieved by incorporating a
semi-crystalline rubber such as VESTENAMER.RTM. in a part of the
sheet material. For example, the innermost layers of the expanding
portion may incorporate VESTENAMER.RTM., whereas the outermost
layers do not. Curing of the material to a unitary body of
hydrocarbon swellable material results in a varying macroscopic
structure across the cross-section of the body, and thus a
variation in permeability to hydrocarbon fluids, even if molecular
cross-linking density is the same across the body.
[0121] The invention provides a swellable apparatus for filling a
space in oil or gas apparatus and method of forming an apparatus is
described. The apparatus comprises a hydrocarbon swellable body
formed from an elastomeric material selected to expand on exposure
to a hydrocarbon fluid such as EPDM. The swellable body has a first
surface which is exposed to a hydrocarbon fluid, a first (inner)
portion, and a second portion disposed between the first portion
and the surface. The first portion comprises a fluid permeability
structure which differs from the fluid permeability structure of
the second portion. In one embodiment, the cross-linking density of
an outer portion of the body is greater than the cross-linking
density of an inner portion of the body.
[0122] The presently described invention provides a number of
benefits. Importantly, it provides apparatus which facilitates
control or selection of swelling characteristics such as swelling
rate during exposure to wellbore fluids. It allows for controlled
swelling behaviour in the presence of both hydrocarbon and water
that may typically be encountered in operations in wells. It
provides for reliability of performance of swellable apparatus in
different conditions.
[0123] Various modifications and improvements may be made without
departing from the scope of the invention herein described.
Combinations of features other than those specifically claimed are
within the scope of the invention.
* * * * *