Expandable connection for use with a swelling elastomer

The present invention generally relates to an apparatus for use in a wellbore. In one aspect, the apparatus includes a first tubular having a connection portion at the end thereof and a second tubular having a mating connection portion at an end thereof. The connection portion and mating connection portion are constructed and arranged to form a connection between the tubulars. The apparatus further includes a swelling elastomer disposable between the connection portion and the mating connection portion, the swelling elastomer expandable upon contact with an activating agent. In another aspect, the invention provides a method for utilizing an expandable connection in a wellbore.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wellbore completion. More particularly, the invention relates to an apparatus and method for attaching and sealing two tubulars. More particularly still, the invention relates to maintaining a seal at the connection point between the two tubulars during the expansion operation.

2. Description of the Related Art

In the drilling of oil and gas wells, a wellbore is formed using a drill bit that is urged downwardly at a lower end of a drill string. After drilling a predetermined depth, the drill string and bit are removed, and the wellbore is typically lined with a string of steel pipe called casing. The casing provides support to the wellbore and facilitates the isolation of certain areas of the wellbore adjacent hydrocarbon bearing formations. The casing typically extends down the wellbore from the surface of the well to a designated depth. An annular area is thus defined between the outside of the casing and the earth formation. This annular area is filled with cement to permanently set the casing in the wellbore and to facilitate the isolation of production zones and fluids at different depths within the wellbore.

It is common to employ more than one string of casing in a wellbore. In this respect, a first string of casing is set in the wellbore when the well is drilled to a first designated depth. The well is then drilled to a second designated depth, and a second string of casing, or liner, is run into the well to a depth whereby the upper portion of the second liner overlaps the lower portion of the first string of casing. The second liner string is then fixed or hung in the wellbore, usually by some mechanical slip mechanism well-known in the art, and cemented. This process is typically repeated with additional casing strings until the well has been drilled to total depth.

Operators are continually searching for means to improve functionality and reduce costs in their drilling operations. This has been achieved in the past in relatively small increments by such things as discrete technological improvements and novel contracting strategies. It is inevitable that these incremental gains are diminishing. The industry needs a radical “next step.” The monobore well is this step.

Monobore wells have a uniform through-bore from the surface casing to the production zones. Today, wells are constructed by progressively securing the borehole with several intermediate casings before the production casing is run. Monobore well technology will eliminate these intermediate casing strings through the use of expandable liners. Monobore wells consist of a sequence of expandable liners that are run through the existing casing, then expanded to achieve the same post-expansion through-bore. A monobore well features each progressive borehole section being cased without a reduction of casing size.

Many conventional wells drilled today consist of a 26-inch or 30-inch conductor and 20-inch or 18 5.8-inch surface casing (or similar sizes), and have several intermediate casings before a 9 5.8-inch production casing is run. The monobore well offers the advantage of being able to start with a much smaller surface casing but still resulting in a 9 5.8-inch production casing. Because top-hole sizes are reduced, less drilling fluid is required and fewer cuttings are created which means less cleaning of the cuttings, and the environmental problem of drilling waste disposal is reduced. Also, with a smaller surface casing size (and only one other actual casing string), the wellhead can be simplified, as can the BOP'S (blow out protectors) and risers. Many drilling plans include a contingency casing or liner to allow for problem zones. Careful planning of a monobore well enables problem zones to be secured without sacrificing a casing size in the well design. Additionally, running expandable liners instead of long casing strings will result in valuable time savings.

Generally, expandable liners for a monobore well or a conventional well are constructed of 38-foot long tubulars. Each expandable liner includes a female thread at the top and a male thread at the bottom. Typically, the top and bottom threaded portions are expandable in the same manner as the expandable liner. A series of expandable liners are commonly screwed together as they are lowered in the wellbore. As the female thread is connected with the male thread, a metal-to-metal seal is created. Additionally, two external O-rings may be disposed on the threads between the two expandable liners to enhance the sealing effect between the male and female thread.

After the entire length of expandable liner is deployed into the wellbore, the expandable liners are typically expanded by the use of a cone-shaped mandrel or by an expander tool. The expander tool is generally run into the wellbore on a tubular string and includes expandable, fluid actuated members disposed on a body. There are a number of advantages to expanding solids using a rotary tool as the expander tool, rather than existing methods involving driving a fixed cone through the pipe. For example, the process is controllable, thereby allowing expansion to be initiated when and wherever required. If necessary, the expander tool can be recovered in a mid-expansion position, and redeployed to continue the operation. Further, the rollers reduce the friction between the tool and the pipe, which allows the expandable liners to be expanded from the top down.

While expanding expandable liners in a wellbore offers obvious advantages, there are problems associated with using the technology. By plastically deforming the expandable liner, the cross-sectional thickness of the expandable liner is necessarily reduced. As a result, the tight metal-to-metal seal created between the female thread and the male thread becomes slack, thereby jeopardizing the seal at the threaded connection. Simply increasing the initial cross-sectional thickness of the expandable liner to compensate for the reduced wall thickness after expansion results in an increase in the amount of force needed to expand the expandable liner.

A need, therefore, exists for an expandable liner connection between two expandable tubulars that maintains its rigidity after the expansion process. There is a further need for an expandable liner connection providing an effective seal at the threaded connection between the expandable liner strings. There is yet a further need for an effective method for ensuring wellbore fluid will not leak through the expandable liners at the threaded connection.

SUMMARY OF THE INVENTION

The present invention generally relates to an apparatus for use in a wellbore. In one aspect, the apparatus includes a first tubular having a connection means at the end thereof and a second tubular having a mating connection means at an end thereof. The connection means and mating connection means are constructed and arranged to form a connection between the tubulars. The apparatus further includes a swelling elastomer disposable between the connection means and the mating connection means, the swelling elastomer expandable upon contact with an activating agent.

In another aspect, the invention provides a method for utilizing an expandable connection in a wellbore. The method includes running an assembly on a tubular string into the wellbore. The assembly includes a first tubular having a connection means, a second tubular having a mating connection means, the connection means and mating connection means are constructed and arranged to form a connection between the tubulars. The assembly also includes a swelling elastomer disposable between the connection means and the mating connection means. The method further includes the steps of applying a force to an inner surface of the connection and expanding the assembly radially outward. The method also includes the step of exposing the swelling elastomer to an activating agent, thereby ensuring that a space within the connection is substantially filled with the swelling elastomer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a cross-sectional view illustrating an expandable liner150of the present invention and a running assembly170being lowered into the wellbore100on a work string140. As depicted, a casing string105is disposed in the wellbore100, however, it should be noted that aspects of this present invention are not limited to use with a partially cased wellbore, but rather can be also be used with a cased or uncased wellbore. An uncased wellbore is known in the industry as an open hole wellbore that typically remains open to provide a flow path for hydrocarbons from the surrounding formation. Thereafter, the wellbore may be closed by employing the present invention in a similar manner as described below.

The running assembly170includes an upper torque anchor160to secure the running assembly170and the expandable liner150in the casing105. As shown inFIG. 1A, the upper torque anchor160is in a retracted position to allow the running assembly170to place the expandable liner150in the desired location for expansion of the liner150. Additionally, a lower torque anchor125, which is disposed below the upper torque anchor160, is used to attach the expandable liner150to the running assembly170. A motor145is disposed at the lower end of the torque anchor125to provide rotational force to turn an expander tool115.

FIG. 1Adepicts the expander tool115with rollers116retracted, so that the expander tool115may be easily moved and placed in the desired location for expansion of the liner150. When the expander tool115has been located at the desired depth, hydraulic pressure is used to actuate the pistons (not shown) and to extend the rollers116so that they may contact the inner surface of the expandable liner150, thereby expanding the liner150into the wellbore100. Generally, hydraulic fluid (not shown) is pumped from the surface to the expander tool115through the work string140.

The expandable liner150includes an upper tubular180having an inner surface183and an outer surface184. The upper tubular180also includes a connection means or a threaded portion182on the inner surface183which is typically known to one skilled in the art as a female thread. As shown, the expandable liner150further includes a lower tubular185having an inner surface188and an outer surface189. Additionally, the lower tubular185includes a connection means or threaded portion187on the outer surface189, which is typically known to one skilled in the art as a male thread. The connecting means of the upper and lower tubulars may be brought together to form a threaded connection175.

FIG. 1Bis an enlarged cross-sectional view illustrating a swelling elastomer205disposed on the threaded connection175between the upper tubular180and the lower tubular185. A coating of the swelling elastomer205may be applied to the threaded portion182of the upper tubular180prior to the connection to the lower tubular185. Thereafter, the threaded portion182on the upper tubular180mates with the threaded portion187on the lower tubular185to form the threaded connection175. In this respect, the swelling elastomer205creates a fluid tight seal between the tubulars180,185by filling the voids between the metal-to-metal seal created in the threaded connection175. Alternatively, the swelling elastomer205may be applied to the threaded portion187on the lower tubular185prior to the connection to the upper tubular180. Alternatively still, the swelling elastomer205may be applied to both the threaded portion182on the upper tubular180and the threaded portion187on the lower tubular185. Preferably, a very thin coat of swelling elastomer205is applied to the threaded portions182,187. However, the thickness of the swelling elastomer205coating may vary depending on the size and the type of thread used to connect the tubulars180,185. Additionally,FIG. 1Billustrates the threaded connection175with the swelling elastomer205. However, it should be understood that this invention is not limited to threaded connections but rather could be used with other types of expandable connections.

In one embodiment, the swelling elastomer205is a cross-linked polymer that will swell multiple times its initial size upon activation by an activating agent. Generally, the activating agent stimulates the polymer chains of the swelling elastomer205both radial and axially. In the preferred embodiment, an activating agent such as a wellbore fluid or some form of hydraulic fluid activates the swelling elastomer205. However, other embodiments may employ different types of swelling elastomers that are activated by other forms of activating agents.

To keep the swelling elastomer205in an inactivated state during the run-in operation, the elastomer205is maintained within a predetermined location. In the preferred embodiment, the threaded portions182,187, substantially enclose the swelling elastomer205, thereby preventing any fluid or activating agent from contacting the swelling elastomer205.

The expandable liner150of the present invention is expanded by the expander tool115acting outwardly against the inside surfaces183,188of the upper and lower tubulars180,185.FIG. 2is an exploded view of an exemplary expander tool115for expanding the liner150. The expander tool115has a body102that is hollow and generally tubular with connectors104and106for connection to other components (not shown) of a downhole assembly. The connectors104and106are of a reduced diameter compared to the outside diameter of the longitudinally central body part of the tool115.

The central body part102of the expander tool115shown inFIG. 2has three recesses114, each holding a respective roller116. Each of the recesses114has parallel sides and extends radially from a radially perforated tubular core (not shown) of the tool115. Each of the mutually identical rollers116is somewhat cylindrical and barreled. Each of the rollers116is mounted by means of an axle118at each end of the respective roller116and the axles are mounted in slidable pistons120. The rollers116are arranged for rotation about a respective rotational axis that is parallel to the longitudinal axis of the tool115and radially offset therefrom at 120-degree mutual circumferential separations around the central body102. The axles118are formed as integral end members of the rollers116, with the pistons120being radially slidable, one piston120being slidably sealed within each radially extended recess114. The inner end of each piston120is exposed to the pressure of fluid within the hollow core of the tool115by way of the radial perforations in the tubular core. In this manner, pressurized fluid provided from the surface of the well, via the work string (not shown), can actuate the pistons120and cause them to extend outward allowing the rollers116contact the inner surfaces183,188of the tubulars180,185.

FIG. 3is a cross-sectional view illustrating the expandable liner150partially expanded into contact with the wellbore100by the expander tool115. The upper torque anchor (not shown) is energized to ensure the running assembly and the expandable liner150will not rotate during the expansion operation. Hydraulic pressure is increased to a predetermined pressure to actuate the pistons in the expander tool115. Upon actuation of the pistons, the rollers116are extended until they contact the inner surface183of the expandable tubular180. The rollers116of the expander tool115are further extended until the rollers116plastically deform the tubular180into a state of permanent expansion. The motor (not shown) rotates the expander tool115during the expansion process, and the tubular180is expanded until the outer surface184contacts the inner surface of the wellbore100. As the expander tool115expands the expandable liner150, the cross-sectional thickness of the expandable liner150is necessarily reduced. Therefore, as the rollers116expand the threaded connection175, the initially tight fit between the threaded portions182,187become slackened, thereby affecting the seal at the threaded connection175. The slacked threaded connection175allows wellbore fluid in an annulus165to contact the swelling elastomer205, thereby causing the polymer chains of the elastomer205to shift positions, and expand the swelling elastomer205both laterally and radially as shown inFIGS. 4A and 4B.

FIG. 4Ais a cross-sectional view of the expandable liner150fully expanded into contact with the surrounding wellbore100. As depicted, the upper tubular180, the threaded connection175and the lower tubular185are fully expanded into the wellbore100. As clearly shown onFIG. 4B, the swelling elastomer205has sealed off any voids in the threaded connection175. In this manner, the liner150of this present invention may be expanded into the wellbore100without any leakage of the wellbore fluid through the threaded connection175of the liner150.

FIG. 4Bis an enlarged cross-sectional view illustrating the swelling elastomer205providing an effective seal at the threaded connection175. As shown, the threaded portions182,187have shifted as the wall of the tubulars180,185became thin during the expansion operation. The slack between the threaded portions182,187breaks the fluid tight seal, thereby allowing wellbore fluid in the annulus to leak through the threaded connection175to expose the swelling elastomer205to the wellbore fluid. Subsequently, the wellbore fluid activates the swelling elastomer205, thereby causing the polymer chains to expand the swelling elastomer205both laterally and radially to fill the voids of the connection. In this manner, the fluid tight seal between the threaded portion182of the upper tubular180and the threaded portion187of the lower tubular185is preserved. As a result, wellbore fluid is prevented from leaking through the threaded connection175.

In operation, the expandable liner assembly and a running assembly are lowered to a desired location in the wellbore on a work string. Thereafter, the upper torque anchor is activated to secure the liner assembly and running assembly in the wellbore. After the expander tool is located at the desired depth, hydraulic pressure is increased to a predetermined pressure to actuate the pistons in the expander tool. Upon actuation of the pistons, the rollers are extended until they contact the inner surface of the expandable liner. The rollers of the expander tool are further extended until the rollers plastically deform the liner into a state of permanent expansion. The motor rotates the expander tool during the expansion process, and the liner is expanded until the outer surface contacts the inner surface of the wellbore. As the expander tool expands the liner, the cross-sectional thickness of the expandable liner is necessarily reduced. Therefore, as the rollers expand the threaded connection, the initially tight fit between the threaded portions become slack, thereby affecting the seal at the threaded connection. The slackness at the threaded connection allows wellbore fluid in the annulus to contact the swelling elastomer, thereby causing the polymer chains of the elastomer to shift positions, and expand the swelling elastomer both laterally and radially to fill the voids in the threaded connection.