SWELLABLE DOWNHOLE PACKERS

Abstract

A swellable packer including a tubular member and a swellable element. The tubular member is disposable on a mandrel configured to be deployed into a wellbore. The swellable element is disposed around the tubular member, and has a first region comprising a swellable material and a second region comprising a degradable or dissolvable material.

Description

FIELD

The subject disclosure generally relates to downhole packers for forming a seal in an annulus. More particularly, the subject disclosure relates to an improved swellable downhole packer.

BACKGROUND

Hydrocarbons are produced from a wellbore that passes through one or more hydrocarbon producing formations.

A packer is a device that is used in a well to form an annular seal between an inner tubular member and a surrounding outer tubular member (a casing string or a liner, as just a few examples) or borehole wall.

Swellable packers are often used to isolate sections of the wellbore from one another, particularly those sections adjacent different hydrocarbon producing formations. Control of the swellable packers swell rate, swell percentage, and the relative hardness of the swellable element is important to assure sufficient engagement with the wellbore wall, and thus efficient isolation of the desired sections of the wellbore.

There exists a need for swellable elements and methods for making swellable elements that have controlled swell rates and increased swell percentages.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

In an embodiment, a packer usable within a wellbore is disclosed. The packer comprises a tubular member, a swellable member circumferentially disposed about an axis of the tubular member which is adapted to swell in the presence of a triggering agent to form an annular seal in the wellbore. The swellable member comprises a first region comprising a swellable material and a second region comprising a degradable or dissolvable material.

In an embodiment, an annular seal is formed using a swellable member longitudinally extending along a tubular member in a wellbore. The swellable member comprises a first region comprising a swellable material, a second region comprising a degradable or dissolvable material. The swellable material is adapted to swell in the presence of a triggering agent to form the annular seal in the wellbore.

In other embodiments, a system usable within a well is disclosed. The system comprises a tubing string to extend downhole in the well and a packer to form an annular seal between the tubing string and a casing or wellbore wall. The packer comprises an inner core and a swellable body mounted to the inner core to swell to form an annular seal in the well. The swellable body comprises a first region comprising a swellable material and a second region comprising a degradable or dissolvable material.

Further features and advantages of the subject disclosure will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject disclosure is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of the subject disclosure, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

FIG. 1 depicts a schematic of a conventional swellable packer in a borehole;

FIG. 2 depicts a schematic of a conventional swellable packer setting in an irregular open hole;

FIG. 3 depicts a swellable packer comprising a laminate structure;

FIG. 4 depicts a graph of the swelling kinetics for a conventional swellable packer and packers with laminate structures as described in the subject disclosure;

FIG. 5 depicts a swellable packer comprising a laminate structure setting in an irregular borehole, e.g., open hole borehole;

FIG. 6A depicts a swellable packer comprising a laminate structure and an external coating; and

FIG. 6B depicts a swellable packer comprising inner layers of swellable material and outer layers of a laminate structure; and

FIGS. 7A and 7B depict a swellable packer comprising a laminate structure and degradable or dissolvable material. The degradable material in the laminate structure is replaced in sections with voids in FIG. 7A and with porous polymers in FIG. 7B.

DETAILED DESCRIPTION

The particulars shown herein are by way of example and for purposes of illustrative discussion of the examples of the subject disclosure only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the subject disclosure. In this regard, no attempt is made to show structural details in more detail than is necessary, the description taken with the drawings making apparent to those skilled in the art how the several forms of the subject disclosure may be embodied in practice. Furthermore, like reference numbers and designations in the various drawings indicate like elements.

Swellable packers are existing commercialized technology in the oil and gas industry. Swellable packer systems are generally composed of at least three components including a swellable element, a base tubular (e.g., base pipe), and rigid end rings. The swellable element is made of an elastomer that imbibes solvent from the surroundings and expands automatically. The tubular or base pipe may be production tubing or another tubular member. The purpose of the packer is to form a seal between this tubular and the casing/formation. Therefore, a certain amount of contact pressure can build up to resist the penetration of liquid from a high-pressure end to a low-pressure end.

The swellable packers that are disclosed herein may take on numerous forms, depending on the particular implementation. As non-limiting examples, in accordance with example implementations, the swellable packers may be gravel packing packers, zonal isolation packers, bridge plugs, and so forth. The swellable packers may be used to form seals inside tubular members, such as casing strings and liners, and may be used to seal against uncased wellbore walls, depending on the particular implementation. The swellable packers that are disclosed herein may be used in a wide variety of downhole operations, such as gravel packing operations, stimulation operations, fracturing operations, production operations, perforating operations, injection operations, testing operations, and so forth. Moreover, the swellable packers that are disclosed herein may be used in temporary workover operations (testing, stimulation and perforating operations, for example), as well as in permanent completions.

In an embodiment, composites of laminate structures comprising swellable elastomer and degradable/dissolvable polymers are used in swellable packers. This composite structure replaces the isotropic and homogenous bulk material used in conventional swellable packers. The advantages of using composites of laminate structures include the ability to optimize the kinetics of swelling, i.e., a first rate which is slow before the degradable/dissolvable polymers degrade or dissolve and a second rate which is faster than the first rate after the degradable/dissolvable polymers degrade or dissolve. In addition, the sealing capability can also be improved for irregular open holes since each layer of swellable material is isolated and therefore can swell to different swelling ratios to fit the borehole.

FIG. 1 depicts a schematic of a conventional packer in a borehole. In FIG. 1, the swellable packer 101 includes a member 105 which is generally tubular, so that fluid may pass through the bore of the set packer. The member 105 can be a downhole tubular such as a pipe or a mandrel, which can be configured to be deployed into a wellbore. The member 105 can also be configured to connect to one or more other downhole members. Accordingly, the member 105 can be incorporated into a completion string, a workstring, or another downhole string. The swellable packer 101 can be used in cased or uncased wellbore. Along a substantial length of this member 105, a swellable elastomeric sleeve-shaped body 109 is positioned over the exterior surface of the member 105. This swellable body is designed to swell in response to a trigger so that swelling creates a seal between the member 105 and the interior surface of either the wellbore or the casing. Initially, the swellable packer 101 is deployed downhole in its unset state, which means the swellable body 109 is radially contracted, i.e., the swellable body 109 has not or at least has not significantly swollen while the tubing string 105 is being run into the wellbore as the swellable body 109 has not yet been exposed for a sufficient time to a triggering agent. After the member 105 is appropriately positioned in the wellbore, the swellable packer 101 is set, which means that the swellable body 109 swells to radially expand so that the swellable body 109 forms an annular seal against the interior surface of the surrounding casing string or wellbore.

The trigger may be any available device or physical parameter known to those of skill in the art to initiate the swelling or expansion of the elastic material, and may include one or more of the following: fluid, gas, temperature, pressure, pH, electric charge, or chemicals. Illustrative fluid triggers include water, hydrocarbons, treatment fluids, or any other fluid known to those skilled in the art. To limit axial movement of the swellable elastomeric body 109 as it radially swells, the packer is provided with end caps or metal rings 103 at each end, with each end being positioned over the exterior surface of the member 105 and secured to the tubular member 105.

The swellable elastomeric sleeve-shaped body 109 includes material that will react with one or more triggers to volumetrically expand or otherwise swell. Non-limiting examples of oil swellable materials that can be used to make at least a portion of body 109 include polyisoprene, polyisobutylene, polybutadiene, natural rubber, polystyrene, poly(styrene-butadiene), polychloroprene, polysiloxane, poly(ethylene-propylene), ethylene propylene diene monomer rubber (EPDM), ethylene vinyl acetate (EVA) rubber, chorosulfonated polyethylene, epichlorohydrin rubber (ECO), polyacrylic rubber (ACM), ethylene acrylic rubber (AEM), silicone rubber such as VMQ, and/or precursors, mixtures, or derivatives thereof. Non-limiting examples of water swellable materials that can be used to make at least a portion of body 109 can include poly(acrylic acid), poly(acrylic acid) potassium salt, poly(acrylic acid) sodium salt, poly(acrylic acid-co-acrylamide), poly(acrylic acid-co-acrylamide) potassium salt, poly(acrylic acid-co-acrylamide) sodium salt, poly(acrylic acid) sodium salt-graft-poly(ethylene oxide), poly(isobutylene-co-maleic acid) sodium salt, poly(methacrylic acid), poly(methacrylic acid) sodium salt, poly(2-hydroxyethyl methacrylate), poly(2-hydroxypropyl methacrylate) and/or precursors, mixtures, or derivatives thereof.

Swellable packers have many advantages when compared to mechanical packers which include low cost, no moving parts, and automatic actuation. A disadvantage of current swellable packers is the lack of control on the actuation time. As shown in FIG. 1, once the geometry of the swellable packer 101 and the borehole size are fixed, the actuation time depends monotonically on a diffusion rate of liquid inside the swellable elastomer. Too fast or too slow of a diffusion rate may create difficulties. If the diffusion rate is fast, the swellable packer may be stuck in an undesired location, while if the diffusion rate is slow, the actuation time may be long and the operational costs tend to increase.

Another disadvantage of the conventional swellable packer is the sealing capability of this type of packer in an irregular open hole. In this type of borehole, the diameter of the borehole varies with depth as shown in FIG. 2. FIG. 2 depicts a conventional swellable packer 201 in an uncased open hole wellbore. The swellable packer 201 includes a tubular member 205.

The swellable packer is provided with end caps or metal rings 209 at each end. FIG. 2 depicts the irregularity of the wellbore and when the swellable packer 201 is in contact with the narrow region of the borehole, stress concentration will generate and prohibit the further swelling of the swellable packer 201. To improve the sealing capability of these conventional packers one approach is to use softer elastomers but the mechanical properties will deteriorate for those swellable packers.

In an embodiment of the subject disclosure, the bulk elastomeric material 109 is substituted with a composite material with a laminate structure comprising swellable materials and degradable or dissolvable materials as shown in FIG. 3. The term laminate material is used to define the microstructure of a special type of composite material, i.e., laminate composite. In such a composite, different phases form a periodically layered structure. A laminate composite is a material with properties that vary in only one direction and that direction is called a laminate direction. This design lends itself to having an increased control of swelling kinetics. In non-limiting examples, the rate of swelling is decelerated before the degradable or dissolvable materials degrade or dissolve respectively and the rate of swelling is accelerated once the degradable or dissolvable material has degraded or dissolved.

The migration of the liquid inside the swellable material can be governed via a diffusion equation:

$\begin{array}{cc}\frac{\partial c}{\partial t}=D{\nabla }^2c,& \left(1\right)\end{array}$

where c is the volume fraction of liquid and D is the diffusion coefficient that depends on the material properties of an elastomer and liquid. See Tanaka, T., and Fillmore, D. J., (1979) “Kinetics of swelling of gels,” Journal of Chemical Physics 70(03): pp. 1214-1218.

As shown in FIG. 4, the volume increment versus time is a continuous curve and actuation time is on the order of W²/D, where W is the distance between the tubing and borehole. There is no control on the kinetics of swelling in situations where the geometries of a packer and a borehole are fixed and the downhole fluid is known.

In an embodiment of the subject disclosure, a laminate composite structure replaces the bulk swellable elastomer used in traditional swellable packers as depicted in FIG. 2. This material comprises laminated swellable elastomers 307 and degradable/dissolvable polymers 305 as depicted in FIG. 3. The swellable packer 301 includes a tubular member 309 and is provided with end caps or metal rings 303 at each end. The time for the degradable material to dissolve may be controlled using different degradable material. Prior to the degradable material dissolving or degrading, the degradable material prohibits swelling of the swellable elastomer as the layers of degradable/dissolvable and swellable material are bonded together.

Therefore, initially the composite material swells slowly as shown in FIG. 4. As the degradable material layer disappears, the surface area for the swellable material increases significantly when compared to a conventional swellable packer. The characteristic length for diffusion becomes Δh<<W and the length of swelling will increase quadratically. For example, in a wellbore with W about 3 inches, the actuation time can be reduced to 1 hour if Δh is taken to be about 0.3 inches. This compares to an actuation time for a conventional swellable packer of about 100 hours. Therefore, in embodiments of the subject disclosure, the kinetics of swelling are slow at the beginning and increase in speed as the degradable material layer disappears.

In an embodiment, the swellable packer can seal an irregular open hole without sacrificing the mechanical properties. As depicted in FIG. 5, a swellable packer 501 is in an uncased open hole wellbore. The swellable packer 501 includes a tubular member 507. The swellable packer is provided with end caps or metal rings 505 at each end. FIG. 5 depicts the irregularity of the wellbore and the swellable packer 501 in contact with the narrow region of the borehole. Because the swellable layers of the laminate structure 503 are isolated from each other, they can swell to different swelling ratios without generating the stress concentration as depicted in FIG. 5.

In other embodiments, dissolvable/degradable polymer material may be coated on the outside of the laminate structure as depicted in FIG. 6A. As depicted in FIG. 6A, a swellable packer 601 is situated in an uncased open hole wellbore. The swellable packer 601 includes a tubular member 611. The swellable packer is provided with end caps or metal rings 609 at each end. As depicted in FIG. 6A, the laminate structure comprising swellable 603 and degradable material 605 is coated with a layer of degradable material 607. This structure will further control the kinetics of swelling. In other embodiments, as depicted in FIG. 6B, a conventional swellable packer 615 comprises an inner swellable layer 613 and an external layer of material comprising a laminate structure of degradable material 605 and swellable 603 material, which controls the kinetics of swelling.

In non-limiting examples, the degradable/dissolvable material include degradable polymers synthesized from mineral origins: aliphatic polyesters (e.g., polylactic acid, polyglycolic acid, polybutylene succinate, polycaprolactone); aromatic polyesters or blends of the two types (e.g., polybutylene succinate terephthalate); polyamides; thermoplastic elastomers; polyvinylalcohols; modified polyolefins (polyethylene or polypropylene with specific agents sensitive to temperature or light). In other embodiments, blends and copolymers of these polymers and their derivatives may be used. Degradable biopolymers from natural origins are also suitable, including six sub-groups: polysaccharides (e.g., starch, cellulose, lignin, chitin); proteins (e.g., gelatine, casein, wheat gluten, silk and wool); lipids (e.g., plant oils including castor oil and animal fats); polyesters produced by micro-organism or by plants (e.g., polyhydroxy-alcanoates, poly-3-hydroxybutyrate); polyesters synthesized from bio-derived monomers (polylactic acid); and miscellaneous polymers (natural rubbers, composites). In addition, a broad range of dissolvable polymers are suitable. Depending on the swelling solvent, oil soluble polymers and water soluble polymers are selected. Oil soluble polymers include un-crosslinked polyisoprene, polyisobutylene, polybutadiene, natural rubber, styrene-butadiene copolymer, polyethylene and polypropylene (low molecular weight), ethylene-propylene copolymer, ethylene-propylene-diene monomer (EPDM) rubber, polydimethylsiloxane, polyurethane, ethylene vinyl acetate (EVA) rubber, chorosulfonated polyethylene, epichlorohydrin rubber (ECO), polyacrylic rubber (ACM), ethylene acrylic rubber (AEM), silicone rubber such as VMQ, etc. Water soluble polymers include polyethylene glycol, polypropylene glycol, polysaccharides (low molecular weight), hydroxyethylcellulose, carboxymethylcellulose, polyacrylic acid, polymethacrylic acid, polyacrylamide, polymethacrylamide, polyethyleneimine, polyvinyl alcohol and a broad range of water soluble polymers derived from polyvinyl alcohol, polyvinyl pyrrolidone, polyoxazoline, etc.

In an embodiment, methods of manufacturing a laminate structure of swellable material and degradable/dissolvable polymers comprises assembling alternating sleeves of swellable materials and degradable/dissolvable polymers on a mandrel. In a non-limiting example, the sleeves are sections of extruded polymer tubes. The laminate structure can be directly bonded to the mandrel using surface bonding agents, or bonded to a metal insert sleeve which can be placed over a mandrel. In non-limiting examples, the layers of swellable materials and degradable/dissolvable polymers are bonded together using heating or molding techniques. In an embodiment, methods of manufacturing a laminate structure of swellable material and degradable/dissolvable polymers include wrapping strips of swellable materials and degradable/dissolvable polymers over a mandrel to a desired thickness. In a non-limiting example, the strips are manufactured by rubber milling.

In an embodiment, the layer of degradable/dissolvable polymers covers the entire surface of the laminate structure as depicted in FIG. 3. In non-limiting examples, this layer is fabricated by (1) sliding a degradable/dissolvable polymer sleeve; (2) wrapping degradable/dissolvable polymer strips using a mandrel wrapping technique; or (3) spraying a thin layer of degradable/dissolvable polymer. The usage of these methods depends on the degradable/dissolvable polymer material and the size of the laminate structure.

In an embodiment, the swellable materials are wrapped over a mandrel and the mandrel is placed into a mold with a desired annulus gap size. The mold is then filled with degradable/dissolvable polymers.

In a further embodiment, the degradable/dissolvable polymers are replaced by voids (no polymer) and a coating as shown in FIG. 7A which allows for fast sealing applications. FIG. 7A depicts a swellable packer 701. The swellable packer 701 includes a tubular member 703. The swellable packer is provided with end caps or metal rings 705 at each end. As depicted in FIG. 7A, the structure comprises swellable material 711 and voids 707 and is coated with a layer of degradable/dissolvable material 709.

In FIG. 7B, the voids are replaced with porous degradable/dissolvable foam 713. The degradable/dissolvable foam is fabricated by adding a blowing agent to the degradable/dissolvable polymers. There are many examples of blowing agents. Non-limiting examples include liquid CO₂, pentane, isopentane, cyclopentane, sodium bicarbonate, or hollow spheres such as glass shells, epoxide shells, PVDC shells, fly ash, etc. The elastic properties of the laminate structures can be modified by using different types of porous polymers. This means the laminate structures can be made stiffer to sustain more differential pressure or be softer to fit the irregular open hole.

Although only a few examples have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the examples without materially departing from this subject disclosure. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.

Claims

1. A packer usable within a wellbore comprising:

a tubular member;

a swellable member circumferentially disposed about an axis of the tubular member and adapted to swell in the presence of a triggering agent to form an annular seal in the wellbore, wherein the swellable member comprises a first region comprising a swellable material; and

a second region comprising a degradable or dissolvable material.

2. The method of claim 1, wherein the first region and second region are alternated on the tubular member.

3. The method of claim 1, wherein the swellable member is formed from a laminate composite material.

4. The packer of claim 1, wherein the triggering agent is a predetermined fluid in the wellbore.

5. The packer of claim 1, wherein the swellable material is one of an oil swellable material or a water swellable material.

6. The packer of claim 1, wherein the first region and second region are bonded together.

7. The packer of claim 1, wherein the swellable member has a first rate of swelling before the second region degrades or dissolves; and

a second rate of swelling which is faster than the first rate of swelling after the second region degrades or dissolves.

8. The packer of claim 1, wherein a surface area of the swellable material increases when the second region degrades or dissolves thus accelerating the rate of swelling.

9. The packer of claim 1, further comprising:

a plurality of first and second regions;

wherein the plurality of first regions each swell to different swelling ratios and conform to a geometry of the wellbore.

10. The packer of claim 1, wherein the swellable member further comprises:

a coating on an outer surface of the swellable member; wherein the coating comprises degradable or dissolvable material.

11. The packer of claim 1, wherein the degradable or dissolvable material is a porous foam material.

12. The packer of claim 1, wherein the swellable member further comprises:

a coating on an inner surface of the swellable member;

wherein the coating comprises swellable material.

13. The packer of claim 1, where the degradable or dissolvable material comprises a plurality of voids.

14. The packer of claim 1, where the degradable or dissolvable material is selected from the group consisting of degradable polymers, degradable biopolymers, dissolvable polymers; and combinations thereof.

15. The packer of claim 1, wherein the wellbore is an open hole wellbore.

16. A method comprising:

forming an annular seal using a swellable member longitudinally extending along a tubular member in a wellbore, wherein the swellable member comprises a first region comprising a swellable material;

a second region comprising a degradable or dissolvable material; and

wherein the swellable material is adapted to swell in the presence of a triggering agent to form the annular seal in the wellbore.

17. The method of claim 16, further comprising:

degrading or dissolving the second region; and

increasing a rate of swelling of the first region.

18. The method of claim 16, wherein the first and second regions are alternatively wrapped about the tubular member.

19. The method of claim 16, wherein the first and second regions are formed from a laminate composite material.

20. A system usable within a well, comprising:

a tubing string to extend downhole in the well; and

a packer to form an annular seal between the tubing string and a casing or wellbore wall, the packer comprising: an inner core; and a swellable body mounted to the inner core to swell to form an annular seal in the well, the swellable body being mounted to and circumscribing the inner core and comprising: a first region comprising a swellable material; and a second region comprising a degradable or dissolvable material.

21. The system of claim 20, wherein the swellable member has a first rate of swelling before the second region degrades or dissolves; and

a second rate of swelling which is faster than the first rate of swelling after the second region degrades or dissolves.