Swellable packer construction for continuous or segmented tubing

A swellable packer construction for continuous or segmented tubing. A method of constructing a swellable packer on a continuous tubular string includes the steps of: attaching a swellable seal material to the tubular string to thereby form the packer; and then wrapping the tubular string with the packer on a spool. A swellable packer includes a tubular body portion for incorporation into a tubular string, and a seal material wrapped about the body portion, the seal material being swellable in response to contact with a fluid. A method of constructing a swellable packer for a tubular string includes the steps of: wrapping a seal material about a tubular body portion to thereby form the packer; and then swelling the seal material in response to contact with a fluid. A continuous tubular string includes a seal material attached to a body portion of the tubular string to thereby form a swellable packer; and the packer wrapped with the tubular string on a spool.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit under 35 USC §§119 and 365 of the filing date of International Application No. PCT/US2006/060094, filed Oct. 20, 2006. The entire disclosure of this prior application is incorporated herein by this reference.

BACKGROUND

The present invention relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a swellable packer construction for continuous or segmented tubing.

Packers and other well tools are typically constructed separate from the remainder of the tubular strings in which they are to be incorporated. In many circumstances, this is a desirable way of constructing well tools, since a position of the well tool in the tubular string may not be known beforehand, and the well tool may be used in different tubular strings.

However, there are other circumstances in which there are disadvantages associated with constructing well tools separate from the remainder of the tubular strings in which they are to be incorporated. For example, if the position of a well tool in a continuous tubular string is known before the tubular string is to be transported to a wellsite, then the well tool could be incorporated into the tubular string at that time, rather than spending time with this operation at the wellsite. As another example, if the position of, or need for, a well tool in a continuous, jointed or segmented tubular string is not known beforehand, then it would be advantageous to be able to construct the well tool at the wellsite, even if a portion of the tubular string has already been installed in a wellbore.

Swellable packers are known in the art. However, prior swellable packers have typically been constructed separate from the tubular strings in which they are to be incorporated.

Therefore, it may be seen that improvements are needed in the art of constructing well tools. In particular, such improvements are needed in the art of constructing swellable packers for continuous or segmented tubular strings.

SUMMARY

In carrying out the principles of the present invention, a swellable packer construction is provided which solves at least one problem in the art. One example is described below in which a swellable packer is constructed on a continuous tubing, and then the packer is wrapped on a spool with the tubing string. Another example is described below in which a swellable seal material is helically wrapped onto a continuous or segmented tubular string. Another example is described below in which a swellable seal material is formed as a cylinder, is split longitudinally, then placed on a continuous or segmented tubular string.

In one aspect of the invention, a method of constructing a swellable packer on a continuous tubular string is provided. The method includes the steps of: attaching a swellable seal material to the tubular string to thereby form the packer; and then wrapping the tubular string with the packer on a spool. The seal material is swellable in response to contact with a fluid.

In another aspect of the invention, a swellable packer is provided which includes a generally tubular body portion configured for incorporation in a tubular string. A swellable seal material is wrapped helically about the body portion. The seal material is swellable in response to contact with a fluid.

In yet another aspect of the invention, a method of constructing a swellable packer for a tubular string includes the steps of: forming a swellable seal material in a cylindrical shape about a mandrel; removing the swellable seal material from the mandrel by splitting it helically; then wrapping a swellable seal material helically about a generally tubular body portion to thereby form the packer; and then swelling the seal material in response to contact with a fluid.

In yet another aspect of the invention, a method of constructing a swellable packer for a tubular string includes the steps of: forming a swellable packer in a cylindrical shape about a mandrel; removing the swellable packer from the mandrel by splitting it longitudinally; then placing it on a continuous or segmented tubular string; and then swelling the seal material in response to contact with a fluid.

In a further aspect of the invention, a continuous tubular string is provided which includes a swellable seal material attached to an integral body portion of the tubular string to thereby form a swellable packer. The swellable packer is wrapped with the tubular string on a spool.

In a still further aspect of the invention, a method of constructing a swellable packer on a tubular string is provided which includes the steps of: inserting the tubular string into a wellbore; and attaching a swellable seal material to the tubular string to thereby form the packer. The attaching step is performed during the inserting step.

These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings, in which similar elements are indicated in the various figures using the same reference numbers.

DETAILED DESCRIPTION

It is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention. The embodiments are described merely as examples of useful applications of the principles of the invention, which is not limited to any specific details of these embodiments.

In the following description of the representative embodiments of the invention, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. In general, “above”, “upper”, “upward” and similar terms refer to a direction toward the earth's surface along a wellbore, and “below”, “lower”, “downward” and similar terms refer to a direction away from the earth's surface along the wellbore.

Representatively illustrated inFIG. 1is a prior art method10of interconnecting a well tool18in a tubular string12. As depicted in the drawing, a lower portion of the tubular string12has already been installed in a wellbore24. A connection20, typically provided with threads and seals, is used to connect the well tool18to the lower portion of the tubular string12.

When the well tool18has been connected at its lower end, the well tool and the lower portion of the tubular string12are lowered further into the wellbore24. These connecting and lowering operations are facilitated by a wellsite crane, workover rig or drilling rig (including drawworks, pipe tongs, floor slips, rotary table, etc.), coiled tubing injector head, or any other type of connecting and lowering means26.

After sufficiently lowering the well tool18, another connector22is connected at an upper end of the well tool18. In the depicted method10, the connector22is provided on a continuous tubing16of the type known to those skilled in the art as “coiled” tubing.

However, note that other types of tubular strings may be used, including segmented tubular strings (such as production tubing, drill pipe, etc.). The lower portion of the tubular string12may also be continuous or segmented.

For example, the lower portion of the tubular string12may be part of the continuous tubing16which is initially installed in the wellbore24. The tubing16is then cut, the connectors20,22are installed on either side of the cut, the well tool18is connected between the connectors, and then the tubular string12is further installed in the wellbore.

It will be readily appreciated that this prior art method10is inconvenient, time-consuming and relatively expensive to perform. Additional expense is incurred at least due to the wellsite equipment needed to cut the tubing16, install the connectors20,22, connect the well tool18in the tubular string12, etc.

If continuous tubing is to be used, it would be much more convenient, economical, etc. to be able to interconnect the well tool18in the tubing16prior to delivering the tubular string to the wellsite. This would eliminate the time and equipment needed to cut the tubing16, install the connectors20,22, etc. at the wellsite. In addition, the separate connecting and lowering means26may not be needed, for example, if a conventional coiled tubing injector head could be used instead.

If segmented tubing is to be used, then certain advantages may also be obtained by using the principles of the invention, some embodiments of which are described below. For example, the well tool18could be constructed or completed after it has been connected to the lower portion of the tubular string12or has otherwise become contiguous with the tubular string.

For both continuous and segmented tubing, it would be advantageous to be able to install a packer externally to the tubing at any location along the tubular string12, without the need for connectors20and22, as it is being lowered into the wellbore24.

Referring additionally now toFIG. 2, a continuous tubular string30embodying principles of the present invention is representatively illustrated. The tubular string30includes the continuous tubing16wrapped on the spool14, as in the method10described above.

However, the tubular string30ofFIG. 2also includes one or more swellable packers32as part of the tubular string. The swellable packers32are preferably incorporated into the tubular string30at predetermined positions and spacings, according to the specifications for a particular well, the swellable packers are wrapped with the remainder of the tubular string on the spool14, and then the tubular string is transported to the wellsite for installation.

One example of a method34for constructing the swellable packers32is representatively illustrated inFIG. 3. This drawing depicts an enlarged view of a tubular body portion36of one packer32.

The body portion36is preferably an integrally formed portion of the overall continuous tubing16. However, the body portion36could be separately formed from the remainder of the tubing, if desired.

An annular recess38is formed on an outer surface of the body portion36. If the body portion36is an integral portion of the tubing16, then the recess38could be formed by, for example, a swaging operation.

If the body portion36is separately formed from the remainder of the tubing16, then the recess38could be formed by, for example, a machining operation. The recess38may be formed in any manner in keeping with the principles of the invention.

A swellable seal material40is positioned in the recess38. Preferably, the seal material40does not extend radially outward beyond the outer surface of the tubing16, so that the packer32can be conveniently wrapped with the tubing on the spool14. However, the seal material40could extend radially outward beyond the outer surface of the tubing16, if desired.

The swellable seal material40swells when contacted by an appropriate fluid. The term “swell” and similar terms (such as “swellable”) are used herein to indicate an increase in volume of a seal material. Typically, this increase in volume is due to incorporation of molecular components of the fluid into the seal material itself, but other swelling mechanisms or techniques may be used, if desired.

When the seal material swells, it expands radially outward into contact with a well surface, such as the inner surface of a casing, liner or tubing string, or the inner surface of a wellbore. Note that swelling is not the same as expanding, although a seal material may expand as a result of swelling.

For example, in conventional packers, a seal element may be expanded radially outward by longitudinally compressing the seal element, or by inflating the seal element. In each of these cases, the seal element is expanded without any increase in volume of the seal material of which the seal element is made.

Various techniques may be used for contacting the swellable seal material with appropriate fluid for causing swelling of the seal material. The fluid may already be present in the well when the packer32is installed in the well, in which case the seal material of the packer preferably includes features (such as absorption delaying coatings or membranes, swelling delayed material compositions, etc.) for delaying the swelling of the seal material. Thus, the seal material40may be part of an overall seal assembly which includes any combination of coatings, membranes, reinforcements, etc.

The fluid which causes swelling of the seal material40may be circulated through the well to the packer32after the packer is in the well. As another alternative, the well fluid which causes swelling of the seal material40may be produced into the wellbore from a formation surrounding the wellbore. Thus, it will be appreciated that any method may be used for causing swelling of the seal material of the packer32in keeping with the principles of the invention.

The fluid which causes swelling of the seal material40could be water and/or hydrocarbon fluid (such as oil or gas). For example, water or hydrocarbon fluid produced from a formation surrounding the wellbore could cause the seal material40to swell.

Various seal materials are known to those skilled in the art, which seal materials swell when contacted with water and/or hydrocarbon fluid, so a comprehensive list of these materials will not be presented here. Partial lists of swellable seal materials may be found in U.S. Pat. Nos. 3,385,367 and 7,059,415, and in U.S. Published Application No. 2004-0020662, the entire disclosures of which are incorporated herein by this reference. However, it should be understood that any seal material which swells when contacted by any type of fluid may be used in keeping with the principles of the invention.

The seal may also be formed from a material with a considerable portion of cavities which are compressed or collapsed at the surface condition. Then, when being placed in the well at a higher pressure, the material is expanded by the cavities filling with fluid. This type of apparatus and method might be used where it is desired to expand the packer in the presence of gas rather than oil or water. A suitable seal material and method are described in International Application No. PCT/NO2005/000170 (published as WO 2005/116394), the entire disclosure of which is incorporated herein by this reference.

Also positioned in the recess38are optional members42, which in this embodiment are wedge-shaped in the cross-sectional view ofFIG. 3. The members42may perform any of several functions in the packer32. For example, the members42may serve to prevent or block extrusion of the seal material40, and/or to grip the well surface to anchor the tubing16in the well, etc.

The members42are displaced radially outward when the seal material40swells. The swelling seal material40biases the members42longitudinally outward, so that they displace along inclined surfaces44at either end of the recess38, thereby also displacing the members radially outward.

The packer32is representatively illustrated inFIG. 4after the seal material40has swollen or expanded in response to contact with fluid. The tubular string30is installed in a wellbore46in which another tubular string48(such as casing, liner, pipe or tubing) has previously been installed.

The seal material40now sealingly engages an interior surface of the tubular string48. Note that the members42have been radially outwardly displaced by the swollen or expanded seal material40.

The members42can block extrusion of the seal material40due to a pressure differential in an annulus50formed between the tubular strings30,48and/or the members can serve to anchor the tubular string30against displacement relative to the tubular string48. If the members42are used as anchoring members, then they may be provided with teeth, serrations or other gripping devices on their outer surfaces.

It is not necessary for the packer32to seal within a tubular string in a well. For example, the packer32could be positioned in an uncased portion of the wellbore46, and the packer could sealingly engage an inner surface of the wellbore itself.

Referring additionally now toFIG. 5, an alternate embodiment of the packer32is representatively illustrated. In this construction of the packer32, the seal material40is not positioned in a recess38on the body portion36. Instead, the seal material40is positioned on the body portion36which has the same, or approximately the same, outer diameter as the tubing string16.

Preferably, the members42are attached to the outer surface of the body portion36and serve to secure and protect the seal material40therebetween, as well as serving to block extrusion of the seal material downhole. The members42could be displaced in response to swelling of the seal material40, in a manner similar to that described above for the embodiment ofFIGS. 2 & 3, if desired.

In a preferred method of constructing the packer32in the embodiments ofFIGS. 2-5, the seal material40is preferably applied to the body portion36, and then the seal material is cured. Swellable seal material curing techniques are well known to those skilled in the art, and so these techniques will not be described further herein.

By applying the seal material40to the body portion36prior to curing the seal material, a continuous and seamless form of the seal material is produced. This method also has advantages when the body portion36is an integral portion of the continuous tubing16, and the seal material40cannot be conveniently slipped over one end of the tubing and properly positioned on the tubing. This method has further advantages when the seal material40is to be positioned in the integral recess38on the body portion36, because the seal material does not have to be stretched over any larger diameter sections of the body portion or tubing16.

It should be clearly understood, however, that it is not necessary for the seal material40to be cured after having been applied to the body portion36. The seal material40could instead be wrapped about the body portion36after having been cured. An example of such a method is described more fully below.

Referring additionally now toFIG. 6, another method52of constructing an alternate embodiment of the swellable packer32is representatively illustrated. In this method52, the seal material40is applied to a generally cylindrical mandrel54, and is then cured.

A cutting tool56(such as a knife, other type of blade or lathe tool, etc.) is then used to cut the seal material40off of the mandrel54. For example, a longitudinal slit may be made through the seal material40, or the mandrel54may be rotated while the cutting tool56is displaced longitudinally along the mandrel (in the direction indicated by the arrow58inFIG. 6), to thereby helically cut the seal material. If helically cut, a pitch of approximately 15-30 cm may be used, with the pitch depending on several factors, such as the diameter of the body portion36on which the seal material40will eventually be installed.

Other techniques for removing the seal material40from the mandrel54after curing may be used in keeping with the principles of the invention. A release agent, lubricant, membrane, film, or other type of release material60may be used between the seal material40and the mandrel54to facilitate removal of the seal material from the mandrel.

Referring additionally now toFIG. 7, the seal material40is depicted after having been helically cut off of the mandrel54, and then helically wrapped about the body portion36. In this manner, this alternate construction of the packer32can be installed on the continuous tubing16or on a segmented tubular string, either prior to or after arriving at the wellsite, or even as the tubular string is being lowered into the wellbore.

As depicted inFIG. 7, the seal material40is wrapped about the body portion36with either no gaps or small gaps62between adjacent wraps of the seal material. The gaps62may remain after the packer32is constructed, in which case the seal material40will preferably close and seal off the gaps when it swells downhole.

The gaps62may result from the mandrel54diameter being different than the continuous tubing16or segmented tubing diameter, or it may result from the cutting process removing some material from the seal material40, or due to the seal material40being applied over a length on the continuous tubing60or segmented tubing which is different than the length of the seal material40on the mandrel54. The gap62should be sufficiently small so that when the seal material40swells or expands due to contact with the fluid in the wellbore, is closes with sufficient compression between adjacent wraps to prevent flow of fluid along the length of the packer32.

The gaps62may be reduced or eliminated when the packer32is constructed by tightening the seal material40about the body portion36, while reducing the length over which the seal material40is installed. This tightening operation may include circumferentially stretching the seal material40about the body portion36while moving a loose end axially closer to a fixed end of the seal material40. One method of doing this is described below.

A segmented ring64is secured to the body portion36, for example, by clamping, welding, fastening, etc. Another segmented ring66is attached at a lower end of the seal material40, for example, by bolting and/or adhesive bonding. The segmented rings64,66are split into two or more circumferential segments so that they can be applied to the continuous body portion36without cutting the body portion or installing the seal material40over one end of the body portion. The rings64,66are engaged with each other (for example, using serrations or another type of locking engagement), so that the ring66and the lower end of the seal material40is prevented from rotating about the body portion36.

After wrapping the seal material40about the body portion36and securing the segmented ring64to the body portion, the seal material is tightened about the body portion by applying torque to another ring68attached at an upper end of the seal material. While tightening, the ring68is moved axially toward rings64,66. This reduces or completely eliminates the gaps62and may apply circumferential tension to the seal material40.

After the tightening operation, the ring68may be secured in position by engagement with another ring70attached to the body portion36. Again, this engagement may be by means of serrations formed on the rings68,70or any other type of locking engagement. The serrations or other locking means may allow one-way rotation of the rings66,68(or either of them) relative to the other rings64,70, so that the seal material40can be tightened around the body portion36from either or both ends thereof.

In another embodiment, rings64,66are combined into one segmented ring, and rings68,70are combined into another segmented ring, where each combined segmented ring is attached by bolting and/or adhesive bonding to the seal material40. The combined segmented rings would be both securable to the body portion36during installation at the wellsite and allow for axial and circumferential adjustment to tighten the seal material40onto the body portion36and eliminate or minimize the gaps62.

A material may be applied between the body portion36and the seal material40before the seal material is tightened about the body portion. For example, this material may serve as a lubricant to facilitate uniform sliding displacement of the seal material40about the body portion36during the tightening process, and then the material may serve as an adhesive and/or sealant to bond the seal material to the body portion after the tightening process and to prevent fluid leakage between the seal material and the body portion.

If the seal material40is removed from the mandrel by cutting a longitudinal slit, then the cylindrically shaped seal material would be spread open at the slit and placed on the body portion36. Adhesive applied between the seal material40and body portion36and/or rings42, or rings64,66or rings68,70, or combinations thereof, may be used to prevent longitudinal movement of the seal material along the body portion.

As described above, the body portion36in the embodiments of the packer32depicted inFIGS. 2-7may be incorporated into continuous or segmented tubular strings. If a continuous tubular string (such as the tubular string30) is used, then the body portion36may be an integrally formed portion of a continuous tubing (such as the tubing16) from which the tubular string is constructed. In this case, the seal material40may be installed on the body portion36before or after the tubular string is transported to the wellsite.

If a segmented tubular string is used, then the body portion36may be included in one of the tubular string segments. In this case, the seal material40may be installed on the body portion36before or after the body portion is contiguous or attached to the tubular string. For example, the body portion36could be connected to a lower portion of the tubular string previously installed in the well, and then the seal material40could be installed on the body portion prior to lowering the body portion into the well.

Such a continuous or segmented tubular string may be used in a workover, completion, retrofit, stimulation, drilling or any other type of operation. The continuous or segmented tubular string may be used in an open hole, cased hole or any other type of wellbore environment.

An adhesive, sealant or any other type of material may be used between the seal material40and the body portion36in any of the embodiments described above, if desired.

As used herein, the term “packer” is used to indicate an annular barrier, for example, for sealing an annulus formed in a well. Thus, a plug (such as a bridge plug, etc.), a hanger (such as a liner or tubing hanger, etc.) and other types of well tools may incorporate a packer therein. The body portion36of the packer32described above could be non-tubular, solid or otherwise prevent fluid communication therethrough if the packer is incorporated into a plug.

Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.