Note: Descriptions are shown in the official language in which they were submitted.
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WATER SENSITIVE POROUS MEDIUM TO CONTROL
DOWNHOLE WATER PRODUCTION AND METHOD THEREFOR
TECHNICAL FIELD
[0001] The present invention relates to apparatus and methods for
controlling the production of fluid through a device in a wellbore and methods
for constructing said apparatus, and more particularly relates, in one non-
limiting embodiment, to apparatus for and methods of inhibiting and
controlling
the flow of water through a wellbore from subterranean formations during
hydrocarbon recovery operations and methods for constructing said apparatus.
TECHNICAL BACKGROUND
[0002] Hydrocarbons such as oil and gas are recovered from a subterra-
nean formation using a wellbore drilled into the formation. Unwanted water
production is a major problem in maximizing the hydrocarbon production
potential of a subterranean well. Tremendous costs may be incurred from
separating and disposing of large amounts of produced water, inhibiting the
corrosion of tubulars contacted by the water, replacing corroded tubular
equipment downhole, and surface equipment maintenance. Shutting off,
preventing and controlling unwanted water production is a necessary condition
to maintaining a productive field.
[0003] Oil and gas wells are typically completed by placing a casing
along the wellbore length and perforating the casing adjacent each such
production zone to extract the formation fluids (such as hydrocarbons) into
the
wellbore. These production zones are sometimes separated or isolated from
each other by installing a packer between the production zones. Fluid from
each production zone entering the wellbore is drawn into a tubing that runs to
the surface. It is desirable to have substantially even drainage along the pro-
duction zone. Uneven drainage may result in undesirable conditions such as an
invasive gas cone or water cone. In the instance of an oil-producing well, for
example, a gas cone may cause an in-flow of gas into the wellbore that could
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significantly reduce oil production. Similarly, a water cone may cause an in-
flow
of water into the oil production flow that reduces the amount and quality of
the
produced oil.
[0004] Accordingly, it is desired to provide even drainage across a pro-
duction zone and/or the ability to selectively close off or reduce in-flow
within
production zones experiencing an undesirable influx of water and/or gas. In
other words, it would additionally be desirable to discover an apparatus and
method which could improve the control of unwanted water production from
subsurface formations.
SUMMARY
[0005] There is provided in one non-limiting embodiment a wellbore
device for controlling a flow of a fluid through a flow path therein. The
wellbore
device includes a container comprising a flow path and a consolidated water
sensitive porous medium (WSPM) packed within the flow path of the wellbore
device container. In turn, the WSPM includes solid particles and at least one
water hydrolyzable polymer at least partially coated on the solid particles.
[0006] There is additionally provided in one non-restrictive version, a
method of constructing a wellbore device for controlling a flow of a fluid
through
a flow path in the wellbore device, where the method involves mixing solid
particles with at least one water hydrolyzable polymer in the presence of a
fluid
that may be water or brine to give a mixture. The method further includes at
least partially drying the mixture. Additionally the method involves packing
the
at least partially dried mixture into the flow path of the container of the
wellbore
device to form a consolidated water sensitive porous medium (WSPM).
[0007] There is also provided, in another non-limiting form, a method for
controlling a flow of a fluid through a flow path in a wellbore device in a
well-
bore. The method involves flowing the fluid through the flowpath in the
wellbore
device and controlling a resistance to flow of the fluid through the flow path
whereby: resistance to flow increases as water content of the fluid increases,
and resistance to flow decreases as water content of the fluid decreases. The
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wellbore device used includes a container (which may be coextensive there-
with) comprising the flow path and a consolidated water sensitive porous
medium (WSPM) packed within the flow path of the wellbore device container.
In turn the WSPM includes solid particles and at least one water hydrolyzable
polymer at least partially coated on the solid particles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic illustration of water sensitive porous media
(WSPM) installed inside a wellbore to control the production of water;
[0009] FIGS. 2A and 2B are schematic illustrations of different water cuts
generating different flow resistance when flowing through a WSPM as a result
of different degrees of polymer chain activation (expansion);
[0010] FIG. 3 is a graph of the pressure differential of WSPM (cross-
linked VF-1 copolymer coated on 20-60 mesh (850-250 micron) NSF
proppant) at 200 F (93 C) with diesel and simulated formation brine (SFB);
[0011] FIG. 4 is a graph of a pressure drop response for different water
cut fluids flowing through WSPM at 200 F (93 C);
[0012] FIG. 5 is a microphotograph of 20/40 mesh (850/425 micron) HSP
ceramic proppant before polymer coating; and
[0013] FIG. 6 is a microphotograph of 20/40 mesh (850/425 micron) HSP
ceramic proppant after polymer coating.
DETAILED DESCRIPTION
[0014] A method has been discovered for building a water sensitive
porous medium (WSPM) to control downhole water production through a
flowpath in a wellbore device installed inside of a wellbore. The WSPM may be
constructed of water-soluble or water-hydrolyzable, high molecular weight
polymers which are coated on solid particles, such as sand, glass beads, and
ceramic proppants. The coated particles are packed under high pressure to
form a consolidated homogenous and high porosity porous medium within a
container of a wellbore device. The container and the wellbore device may be
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separate structures, where the container is part of the wellbore device, or
the
container and the wellbore device may be the same and coextensive. After the
polymers are fully hydrolyzed in water or brine, the polymers may be
optionally
crosslinked with crosslinking agents. The solid particles may be mixed with
the
polymer solution, e.g. in a blender or mixer, at a particular ratio.
[0015] As a blender or mixer is continuous stirring the mixture of solid
particles and polymer solution, blowing ambient air, hot air, nitrogen, or
vacuuming is applied to the mixture to at least partially or completely dry
the
polymer. The polymer coated particles are loaded into a container to pack into
consolidated porous medium at high pressure. The packed container, as part of
a downhole tool, is installed in a wellbore. When formation water is flowed
through the WSPM interstitial flow channels, the coated polymers extend their
polymer chains into the pore flow channels, resulting in increased fluid flow
resistance. Conversely, when oil flows through the WSPM, the polymer chains
shrink back to open the flow channels wider for the desired oil flow. This
process has been demonstrated to be repeatable and reversible as water/oil
fluid composition varies.
[0016] When water mixed with oil flows through the WSPM, the magni-
tude in pressure drop across the flow channels depends on the percentage of
water in the mixture (water/oil ratio, or WOR). Higher water cuts result in
higher
resulting pressure drops. As will be discussed, lab testing data has confirmed
that pressure drops across WSPM change with water percentage of flowing
through fluids.
[0017] More specifically, the production of unwanted subterranean
formation water may be prevented, controlled or inhibited by a method
involving
treating particles with high molecular weight, water-hydrolyzable polymers,
and
incorporating the particles into a water sensitive porous medium (WSPM) in a
wellbore device placed within the wellbore. The polymer-coated particles are
introduced into a container of a wellbore device under high pressure to form a
consolidated WSPM in the device before its introduction downhole.
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[0018] Generally, the relatively high molecular weight polymers that have
components or functional groups that anchor, affiliate or attach onto the
surface
of the solid particles. The polymers are hydrophilic and/or hydrolyzable mean-
ing they swell or expand in physical size upon contact with water. The average
particle size of the particles may range from about 10 mesh to about 100 mesh
(from about 2000 microns to about 150 microns). Alternatively, the average
particle size of the particles may range from about 20 mesh independently to
about 60 mesh (from about 840 microns to about 250 microns); where the term
"independently" means that any lower threshold may be combined with any
upper threshold. Thus, it should be understood that the solid particles which
serve as a substrate to the water hydrolyzable polymer are relatively small,
particulate matter, but should not be confused with atomic particles or sub-
atomic particles.
[0019] The particles may be any of a wide variety of solid particulate
material; suitable materials include, but are not necessarily limited to,
sand,
glass beads, ceramic beads, metal beads, bauxite grains, walnut shell frag-
ments, aluminum pellets, nylon pellets and combinations thereof, including
conventional proppants and gravel, and, including proppants and gravel of to-
be-developed materials. Proppants are known in the oilfield as sized particles
typically mixed with fracturing fluids to hold open fractures after a
hydraulic
fracturing treatment. Proppants are sorted for size and sphericity to provide
an
effective conduit for the production of oil and/or gas from the reservoir to
the
wellbore. "Gravel" has a particular meaning in the oilfield relating to
particles of
a specific size or specific size range which are placed between a screen that
is
positioned in the wellbore and the surrounding annulus. The size of the gravel
is selected to prevent the passage of sand from the formation through the
gravel pack.
[0020] Further, the solid particles, e.g. proppants or gravel, may suitably
be a variety of materials including, but not necessarily limited to, sand (the
most
common component of which is silica, i.e. silicon dioxide, Si02), glass beads,
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ceramic beads, metal beads, bauxite grains, walnut shell fragments, aluminum
pellets, nylon pellets and combinations thereof.
[0021] The particles may be coated by a method that involves at least
partially hydrolyzing the polymer in a liquid including, but not necessarily
limited
to, water, brine, glycol, ethanol and mixtures thereof. The particles are then
inti-
mately mixed or contacted with the liquid containing the polymer to contact
the
surfaces of the particles with the polymer. The liquid is then at least
partially
vaporized or evaporated through vacuum, or the use of heat and/or contact
with a dry gas such as air, nitrogen, or the like. The coating method may be
conducted at a temperature between ambient up to about 200 F (about 93 C),
to facilitate quick drying of the coating. It may not be necessary in some
embodiments to completely dry the coating.
[0022] The loading of the polymers may be a ratio of weight of solid
particles to weight of dry water hydrolyzable polymer ranging from about
10,000:1 to about 10:1; alternatively ranging from about 500:1 independently
to
about 25:1. The solid particles should be at least partially coated by the
polymer; that is, while it is desirable to completely coat the solid particles
with
the polymer, the method and apparatus may still be considered successful if
the particles are at least partially coated to the extent the WSPM functions
effectively for the purposes noted herein.
[0023] The high pressure used to pack the water hydrolyzable polymer
coated particles into the container of the wellbore device through which the
flow
path exists may range from about 50 to about 2000 psi (about 0.3 to about 13.8
MPa), alternatively from about 100 independently to about 1000 psi (about 0.7
to about 6.9 MPa).
[0024] The WSPM placed in the wellbore will control unwanted formation
water flowing through the wellbore while not adversely affecting the flow of
oil
and gas. When water flows into the WSPM, the polymers anchored on the solid
particles expand to reduce the water flow channel and increase the resistance
to water flow. The polymers may be understood to interact chemically,
ionically
or mechanically with a component of the produced or in-flowing formation
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fluids, e.g. water molecules. This desired response may be variously described
as resistance, permeability, impedance, etc., where the flow of hydrocarbons
(e.g. oil and gas) is desirable, but the flow of water is not. This
interaction
varies the resistance to flow across the flow path of the wellbore device.
When
oil and/or gas flow through this special porous media, the polymers shrink to
open the flow channel for oil and/or gas flow. The pre-treated particles,
(e.g.
proppants) are expected to form homogeneous porous media with the polymer
uniformly distributed in the media to increase the efficiency of the polymer
controlling unwanted water production.
[0025] In more detail, suitable water hydrolyzable polymers include those
having a weight average molecular weight greater than 100,000. Suitable, more
specific examples of water hydrolyzable polymers include, but are not neces-
sarily limited to, homopolymers and copolymers of acrylamide, sulfonated or
quaternized homopolymers and copolymers of acrylamide, polyvinylalcohols,
polysiloxanes, hydrophilic natural gum polymers and chemically modified deriv-
atives thereof. Crosslinked versions of these polymers may also be suitable,
including but not necessarily limited to, crosslinked homopolymers and copoly-
mers of acrylamide, crosslinked sulfonated or quaternized homopolymers and
copolymers of acrylamide, crosslinked polyvinylalcohols, crosslinked polysilox-
anes, crosslinked hydrophilic natural gum polymers and chemically modified
derivatives thereof. Further specific examples of suitable water hydrolyzable
polymers include, but are not necessarily limited to, copolymers having a
hydrophilic monomeric unit, where the hydrophilic monomeric unit is selected
from the group consisting of ammonium and alkali metal salt of acrylamido-
methylpropanesulfonic acid (AMPS), a first anchoring monomeric unit based on
N-vinylformamide and a filler monomeric unit, where the filler monomeric unit
is
selected from the group consisting of acrylamide and methylacrylamide. Addi-
tional suitable water hydrolyzable polymers include, but are not necessarily
limited to, copolymers of vinylamide monomers and monomers containing
ammonium or quaternary ammonium moieties, copolymers of vinylamide
monomers and monomers comprising vinylcarboxylic acid monomers and/or
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vinylsulfonic acid monomers, and salts thereof, and these aforementioned
copolymers further comprising a crosslinking monomer selected from the group
consisting of bis-acrylamide, diallylamine, N,N-diallylacrylamide, divinyloxy-
ethane, divinyldimethylsilane.
[0026] In an optional embodiment, when the polymers are fully or
essentially completely hydrolyzed, they may be cross-linked to increase their
molecular weight. Suitable crosslinking agents include, but are not
necessarily
limited to, aluminum, boron, chromium, zirconium, titanium, and other
inorganic
based and organic based crosslinking agents and other conventional crosslink-
ing agents.
[0027] These polymers are sometimes referred to as relative permeabil-
ity modifiers (RPMs) and more information about RPMs suitable to be of use in
the method and compositions described herein may be found in U.S. Pat. Nos.,
5,735,349; 6,228,812; 7,008,908; 7,207,386 and 7,398,825.
[0028] Shown in FIG. 1 is a schematic illustration of an oil well 10 having
a wellbore 12, which happens to be vertical in part and horizontal in part, in
a
subterranean formation 14 that contains both oil and water. Water sensitive
porous media (WSPM) within wellbore devices 16 have been installed at four
locations between packers 18 along the horizontal section of the wellbore 12
to
control the production of water. The flow of oil from the formation 14 into
the
wellbore 12 is schematically indicated by black arrows 20, whereas the flow of
water is schematically indicated by gray arrows 22. The flow of oil 20 is
uninhi-
bited by the WSPM due to the lack of resistance of the unhydrolyzed polymer,
whereas the flow of water is inhibited by the increased resistance of the
hydrolyzed polymer, as indicated by the lower water flow at small gray arrows
24.
[0029] Shown in FIG. 2 is a schematic illustration of different water cuts
generating different flow resistance when flowing through a WSPM 16 as a
result of different degrees of polymer chain activation (expansion). As pre-
viously discussed, the WSPM 16 includes solid particles 30 having water
hydrolyzable polymers 32 at least partially coated thereon or adhered thereto.
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The water droplets are schematically represented by gray circles 34 and the
oil
droplets are schematically represented by black circles 36. FIG. 2A schemati-
cally illustrates the WSPM 16 where a 25% water cut flows in the direction
shown (left to right) where the relatively low amount of water droplets 34
cause
a relatively small amount of the polymer 32 to swell, enlarge or hydrolyze
increasing resistance to flow. FIG. 2B schematically illustrates the WSPM 16
where a larger 50% water cut flows in the direction shown (left to right)
where
the relatively equal amount of water droplets 34 compared to the oil droplets
36
cause a relatively larger amount of the polymer 32 to swell, enlarge or hydro-
lyze further increasing resistance to flow, as compared with FIG. 2A.
[0030] The invention will now be illustrated with respect to certain exam-
ples which are not intended to limit the invention in any way but simply to
further illustrated it in certain specific embodiments.
EXAMPLES
[0031] FIG. 5 is a microphotograph of 20/40 mesh (850/425 micron)
NSF ceramic proppant before polymer coating. HSP proppant is available
from Carbo Ceramics. FIG. 6 is a microphotograph of the same 20/40 mesh
(850/425 micron) HSP ceramic proppant after polymer coating. It may be seen
that each proppant particle in FIG. 6 is fully coated and bonded by the
polymer
using the coating method described.
[0032] One non-limiting packing procedure for building a WSPM as a
water sensitive flow channel (WSFC) is set out in Table I. The procedure
involves packing polymer coated proppants into 1 inch (2.5 cm) ID and 12 inch
(30 cm) long stainless steel tube with both end caps forming a uniform porous
medium.
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TABLE I
Packing Procedure
1) The stainless steel tube (container, simulating a wellbore device) is
affixed on one end with an end cap; a 100 mesh (150 micron) stainless
screen is laid inside the end cap to hold the polymer coated proppants;
2) The stainless steel tube is placed into a compressor with open end up;
3) One spoon of polymer coated proppants (about 5 grams) is loaded
inside of the tube, and a 0.97 inch (2.5) ID and 18 inch-long (45.7 cm)
alumina rod is put against the proppants inside of the tube;
4) 1200 pound force from a compressor is loaded onto the alumina rod to
compress the polymer coated proppants into a consolidated porous
medium;
5) Steps 3) and 4) are repeated until the length of the porous medium
reaches desired porous medium length;
6) Another 100 mesh (150 micron) stainless screen is affixed on the top of
the stainless steel tube;
7) Stainless steel spacers are added into the tube if there is any open
space inside of the tube; and
8) The top end cap was tightened and the tube is ready for testing.
[0033] FIG. 3 is a graph of the pressure differential of crosslinked VF-1
copolymer coated on 20-60 mesh (850-250 micron) HSP proppant at 200 F
(93 C) with diesel and simulated formation brine (SFB). VF-1 is a cross-linked
vinylamide-vinylsulfonate copolymer. The HSP proppants were coated with the
VF-1 polymer as described above. The polymer loading was 0.4 % bw (by
weight) of the proppant weight. FIG. 3 is a response test graph showing that
the pressure differential of the polymer-coated proppant WSPM placed inside
of a 12-inch long, 1-inch ID stainless steel tube (about 30 cm long by about
2.5
cm ID) changes when pumping with oil (diesel in this Example) relative to
pumping with formation water (Simulated Formation Brine or SFB) flowing
through the pack. This graph demonstrates that the pack exhibits high flow
resistance for water and low flow resistance for oil.
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[0034] FIG. 4 is a graph of a pressure drop response for different water
cut fluids flowing through a WSPM at 200 F (93 C). The fluids were blends of
brine and diesel. With increasing amounts of water (greater water cut percen-
tage), the higher the pressure drop. The WSPM was made from VF-1 coated
50-60 mesh (297 to 250 micron) ceramic proppants with polymer loading 0.4%.
Different water cuts are marked on FIG 4.
[0035] In the foregoing specification, the invention has been described
with reference to specific embodiments thereof, and has been demonstrated as
effective in providing methods for inhibiting and controlling water flow
through
wellbores, particularly wellbore devices having flow paths containing solid
particles coated with a water hydrolyzable polymer. However, it will be
evident
that various modifications and changes can be made thereto without departing
from the broader scope of the invention as set forth in the appended claims.
Accordingly, the specification is to be regarded in an illustrative rather
than a
restrictive sense. For example, specific combinations of solid particles,
water
hydrolyzable polymers, wellbore devices and other components falling within
the claimed parameters, but not specifically identified or tried in a
particular
composition or method, are expected to be within the scope of this invention.
Further, it is expected that the components and proportions of the solid
particles and polymers and steps of constructing the wellbore devices may
change somewhat from wellbore device to another and still accomplish the
stated purposes and goals of the methods described herein. For example, the
assembly methods may use different pressures and additional or different
steps than those exemplified herein.
[0036] The words "comprising" and "comprises" as used throughout the
claims is interpreted "including but not limited to".
[0037] The present invention may suitably comprise, consist or consist
essentially of the elements disclosed and may be practiced in the absence of
an element not disclosed. For instance, a wellbore device for controlling a
flow
of a fluid through a flow path may consist of or consist essentially of a
container
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comprising a flow path and a consolidated water sensitive porous medium
(WSPM) packed within the flow path of the wellbore device container, where
the WSPM consists of or consists essentially of solid particles and at least
one
water hydrolyzable polymer at least partially coated on the solid particles.
