Patent Description:
In many well applications, a wellbore is drilled and a casing string is deployed along the wellbore. A liner hanger system may then be used to suspend liner/casing downhole within the casing string via a liner hanger. The liner hanger system may be a mechanically operated system or a hydraulically operated system. However, hydraulically operated systems generally have greater versatility and allow the liner to be rotated during running in hole. While running in hole, fluid is circulated downhole under pressure to facilitate deployment of the liner. However, circulating the fluid at higher flow rates can generate high circulating pressures which run the risk of prematurely setting the liner hanger and/or releasing a running tool used to deploy the liner hanger. Attempts have been made to restrict such premature actuation, but current systems can be complicated or may not render the liner hanger system immune from premature hydraulic actuation.

In general, a methodology and system are provided for reducing or eliminating the risk of premature actuation of a liner hanger system and/or premature release of a running tool. According to forms of this disclosure, the technique utilizes a liner hanger system having a running string and a liner hanger assembly which may include a liner top packer assembly. The liner hanger assembly comprises a liner hanger which may be actuated at a desired location to suspend a liner/casing from a surrounding casing string. The liner hanger system utilizes an anti-preset module which may be used in cooperation with the liner hanger to prevent premature actuation of the liner hanger. By way of example, the anti-preset module may use pressure equalization between a region within the running string and a region between the running string and the liner hanger to prevent pressure imbalances which could actuate the liner hanger. A locking mechanism with releasable dogsis used to temporarily lock the liner hanger against premature actuation. The anti-preset module may be used to avoid premature setting of the liner hanger, while pressure equalization inside and outside the hanger running tool, e.g. inside and outside a collet running tool, may be used to avoid premature release of the hanger running tool.

Document <CIT> relates to a liner hanger assembly for hanging a liner in a well, and to an improved slip releasing mechanism within the downhole tool.

However, many modifications are possible within the scope of this disclosure as defined in the claims.

Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:.

In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The disclosure herein generally involves a methodology and system for reducing or eliminating the risk of premature actuation of a liner hanger system and/or premature release of a running tool. According to an embodiment, the technique utilizes a liner hanger system having a running string and a liner hanger assembly. The liner hanger assembly comprises a liner hanger which may be actuated at a desired location within a borehole, e.g. within a casing. The liner hanger assembly further comprises a liner/casing which may be suspended from a surrounding casing string via the liner hanger.

The liner hanger system utilizes an anti-preset module which may be used in cooperation with the liner hanger to prevent premature actuation of the liner hanger. Additionally, the system may utilize features to avoid premature release of the liner hanger running tool. By way of example, the anti-preset module may use pressure equalization between a region within the running string and a region between the running string and the liner hanger to prevent pressure imbalances which could actuate the liner hanger. Additionally, a locking mechanism, e.g. releasable dogs, may be used to temporarily lock the liner hanger against premature actuation. According to an embodiment, the anti-preset module may be used to avoid premature setting of the liner hanger, while pressure equalization inside and outside the hanger running tool, e.g. inside and outside a collet running tool, may be used to avoid premature release of the hanger running tool.

As described in greater detail below, the system helps enable circulation of fluids at relatively high rates and pressures during deployment of the liner and liner hanger. According to an embodiment, a running string extends into the liner hanger and liner in a manner which creates an inner pressure region within the running string and an intermediate pressure region between the running string and the liner hanger/liner. The configuration of the overall system allows pressure to substantially equalize within both regions. Additionally, the locking mechanism of the anti-preset module is used to mechanically lock the liner hanger against premature actuation. For example, the locking mechanism may be used to mechanically lock a hydraulic cylinder of the liner hanger in a run-in-hole position.

The liner hanger may be set by dropping a ball down through the running tool to a ball seat to thus enable creation of a pressure differential between the inner pressure region and the intermediate pressure region. By relatively increasing the pressure within the inner pressure region, the locking mechanism is released to enable actuation of the liner hanger. In some embodiments, a shear member, e.g. shear screws, also may be used so that pressuring up the running string initially shears the shear screws. Prior to dropping the ball, fluid circulation may be performed at desired rates within the system without risking premature shearing of the shear member or actuation of the liner hanger. Once the ball is dropped to temporarily plug the anti-preset module, however, a pressure differential can be created between the inner pressure region and the intermediate pressure region. The pressure differential may be continuous or established at different levels to achieve desired results, e.g. release of the locking mechanism to enable actuation of the liner hanger while also allowing release of the liner hanger running tool. By way of example, the pressure differential may be used to first set the liner hanger and to subsequently release the running string for removal.

Referring generally to <FIG>, an example of a liner hanger system <NUM> is illustrated as being run-in-hole into a borehole <NUM>, e.g. a wellbore, lined with or otherwise having a casing <NUM>. In this embodiment, the liner hanger system <NUM> comprises a liner hanger assembly <NUM> having tubing <NUM>, e.g. a liner string, coupled with a liner hanger <NUM>. The overall liner hanger system <NUM> further comprises a releasable running string <NUM> which is releasably coupled with the liner hanger assembly <NUM>. The liner hanger <NUM> works in cooperation with an anti-preset module <NUM> to prevent premature actuation/setting of the liner hanger <NUM> into engagement with the surrounding casing <NUM>.

Depending on the parameters of a given operation, the liner hanger system <NUM> also may comprise other components/assemblies enabling interaction between the liner hanger assembly <NUM> and the running string <NUM>. For example, the overall liner hanger system <NUM> may further comprise a pack off coupling section <NUM>, a collet running tool (CRT) section <NUM>, and a packer section <NUM>. The packer section <NUM> may include a liner top packer assembly having a packer <NUM> which is part of or combined with the overall liner hanger assembly <NUM>. In the illustrated example, the packer <NUM> is part of the liner hanger assembly <NUM> and is located below the collet running tool section <NUM> and above the liner hanger <NUM>. The packer section <NUM> may have a variety of configurations and may comprise various slips, sealing elements, and other components to facilitate actuation and engagement with the surrounding casing <NUM>.

In the illustrated example, the liner hanger <NUM> comprises various features such as a cone <NUM> having inclined surfaces which interact with slips <NUM>. The slips <NUM> may be coupled with one or more hydraulic cylinders <NUM>. Once the liner hanger <NUM> is released for actuation via the anti-preset module <NUM>, pressure applied down through the running string <NUM> may be used to actuate at least one of the cylinders <NUM> so as to shift the slips <NUM> linearly with respect to the cone <NUM>. This relative linear movement of the slips <NUM> against the sloped surfaces of cone <NUM> effectively forces the slips <NUM> in a radially outward direction and ultimately into secure engagement with the surrounding casing <NUM>.

Referring generally to <FIG>, a cross-sectional illustration of the pack off coupling section <NUM> is illustrated. In this example, the running string <NUM> comprises a running tool <NUM>, a portion of which is illustrated in cross-section in <FIG>. The running tool <NUM> is disposed within a tubular section <NUM>, e.g. a tieback receptacle, of the overall liner hanger assembly <NUM>. By way of example, the illustrated portion comprises a mandrel <NUM> and at least a portion of a pack off coupling <NUM> coupled to the running tool <NUM> as part of the running string <NUM>. The pack off coupling <NUM> includes a pack off coupling mandrel <NUM> which forms part of the overall mandrel <NUM>. A seal <NUM> surrounds pack off coupling mandrel <NUM> and is captured linearly between an abutment <NUM> and a retention mechanism <NUM>. The seal <NUM> is positioned to form a seal between the mandrel <NUM> and the surrounding tubular section/tieback receptacle <NUM>. It should be noted that seal <NUM> of pack off coupling <NUM> could be an integral component of running tool <NUM>.

As illustrated, the configuration provides an inner pressure region <NUM> within the running tool <NUM>, e.g. within an internal passage <NUM> of the running tool <NUM>, and an intermediate pressure region <NUM>. The intermediate pressure region <NUM> is located between the running tool <NUM> and the liner hanger assembly <NUM>. It should be noted the internal passage <NUM> extends down through the running tool <NUM> and enables circulation of fluids under relatively high pressure during running-in-hole. However, the internal passage <NUM> also effectively is in communication with the intermediate pressure region <NUM> located externally of the running tool <NUM> and within the liner hanger assembly <NUM>. For example, the pressure regions <NUM>, <NUM> may be in communication with each other around a bottom end of the running tool <NUM> and/or via suitably located ports. This allows the inner pressure region <NUM> to remain substantially pressure balanced with the intermediate pressure region <NUM> below pack off coupling <NUM> while running-in-hole. The pressure balancing helps reduce the chance of premature actuation of the liner hanger <NUM> and/or premature release of the running string <NUM> from the liner hanger assembly <NUM>.

Referring generally to <FIG>, an example of CRT section <NUM> is illustrated. In this embodiment, the running tool <NUM> of running string <NUM> may be coupled with the liner hanger assembly <NUM> at CRT section <NUM>. As illustrated, the CRT section <NUM> may comprise a CRT piston <NUM> slidably mounted around running tool mandrel <NUM>. The CRT piston <NUM> is operatively coupled with packer <NUM> via a collet <NUM> and connector mechanism <NUM>, thus connecting the running string <NUM> to liner hanger assembly <NUM>. While inner pressure region <NUM> is open, pressure cannot build to shift the CRT piston <NUM>. Therefore, running string <NUM> and packer <NUM> are not prematurely released. Effectively, the structure of CRT piston <NUM> and the overall CRT section <NUM> allows the pass-through of pressure along intermediate pressure region <NUM> and up to pack off coupling <NUM>. This allows pressure to equalize between pressure regions <NUM> and <NUM>, thus preventing premature release of piston <NUM> and running string <NUM>. It should be noted that collet running tool section <NUM> could be constructed as a different type of running tool section, e.g. a hydraulic running tool section using a hydraulic running tool or a hydro mechanical running tool section using a hydro mechanical running tool instead of a collet running tool.

However, once the inner pressure region <NUM> is blocked (e.g. by dropping a ball as explained in greater detail below), increased pressure may be applied along inner pressure region <NUM> relative to pressure region <NUM>. This increased pressure acts on CRT piston <NUM> via passages <NUM>. Sufficient pressure in inner pressure region <NUM> relative to intermediate pressure region <NUM> causes the CRT piston <NUM> to shift linearly along mandrel <NUM> (shift to the left in the example illustrated in <FIG>) which, in turn, shifts collet <NUM> via mechanism <NUM> to a release position. Shifting the collet <NUM> to the release position also releases packer <NUM> and running string <NUM>. After the packer <NUM> and running string <NUM> are released, the packer <NUM> may be set by, for example, mechanically slacking off weight on the string and thus slacking off weight on the packer <NUM>. Additionally, the running string <NUM> may be withdrawn to the surface. It should be noted that some embodiments may utilize a shear member <NUM>, e.g. shear screws, which initially hold CRT piston <NUM> in place until sufficient pressure builds along inner pressure region <NUM>.

Referring generally to <FIG>, an example is illustrated of the anti-preset module <NUM> and liner hanger setting features. In <FIG>, for example, a portion of the running tool <NUM> is illustrated as having a bypass module <NUM> disposed generally within one of the cylinders <NUM>, e.g. the upper of the two illustrated cylinders <NUM>. However, the bypass module <NUM> may be located at other positions. In the illustrated example, the bypass module <NUM> is sealably engaged with a surrounding tubular structure <NUM> of liner hanger assembly <NUM> via seals <NUM>. As illustrated, the tubular structure <NUM> may be positioned along the interior of cylinders <NUM>.

The bypass module <NUM> comprises longitudinal passages <NUM> which extend in a generally axial direction past seals <NUM> so as to allow pressure equalization between the inner pressure region <NUM> and the overall intermediate pressure region <NUM> above and below seals <NUM>. However, the bypass module <NUM> also comprises radially oriented ports or passages <NUM> extending between inner pressure region <NUM> and intermediate pressure region <NUM>. As further illustrated in <FIG>, the radial passages <NUM> are located so as to remain isolated with respect to the longitudinal bypass passages <NUM>. It should be noted that corresponding passages <NUM>, e.g. radial passages, are formed through tubular structure <NUM> to enable communication between intermediate pressure region <NUM> and an actuation region <NUM> of at least one corresponding hydraulic cylinder <NUM>, e.g. the upper cylinder <NUM>. As explained in greater detail below, once flow along inner pressure region <NUM> is blocked, the pressure within region <NUM> may be increased. This relatively increased pressure is translated through passages <NUM>, through corresponding passages <NUM>, and into actuation region <NUM>. Sufficient pressure is able to cause linear shifting of the corresponding cylinder(s) <NUM>, relative to tubular structure <NUM>, and thus actuation of slips <NUM> to set liner hanger <NUM>.

With additional reference to <FIG>, an example of the anti-preset module <NUM> is illustrated as comprising a module piston <NUM> slidably mounted around running tool mandrel <NUM>. Appropriate seals <NUM> are positioned between module piston <NUM> and mandrel <NUM> to form an actuation chamber <NUM> which is in fluid communication with inner pressure region <NUM> via at least one passage <NUM>, e.g. a plurality of radial passages.

The module piston <NUM> may be connected with a lower sleeve <NUM> slidably connected and rotationally restricted via a pin or pins <NUM> slidably received in a corresponding slot or slots <NUM> formed along the exterior of mandrel <NUM>. Similarly, the module piston <NUM> is illustrated as connected with an upper sleeve <NUM> slidably connected and rotationally restricted via a pin or pins <NUM> slidably received in a corresponding slot or slots <NUM>.

In this embodiment, the anti-preset module <NUM> further comprises a locking mechanism <NUM> which locks the liner hanger <NUM> against actuation while, for example, running-in-hole. By way of example, the locking mechanism <NUM> may comprise a plurality of dogs <NUM> mounted in and retained in the liner hanger <NUM>. For example, the dogs <NUM> may be mounted in corresponding recesses <NUM> formed along the exterior of tubular structure <NUM>. The dogs <NUM> each include a base portion <NUM> which extends through a corresponding opening <NUM> formed radially through tubular structure <NUM> (see also <FIG>).

Prior to actuation of liner hanger <NUM>, e.g. during running-in-hole, the base portion <NUM> of each dog <NUM> is in contact with an exterior surface of upper sleeve <NUM>. The upper sleeve <NUM> holds each of the dogs <NUM> in a radially extended position and in engagement with a corresponding retention recess <NUM> located along an interior of the corresponding cylinder <NUM>, e.g. the lower of the two illustrated cylinders <NUM>, thus preventing linear movement of the corresponding cylinder <NUM> in a liner actuation direction. Additionally, each dog <NUM> may be spring biased in the radially outward direction by, for example, a suitable spring member <NUM>.

Once the liner hanger <NUM> is at a desired position for setting of slips <NUM>, a ball <NUM> is dropped down through the internal passage <NUM> of running string <NUM> and running tool <NUM> until engaging a corresponding ball seat <NUM> to prevent flow along internal passage <NUM>. It should be noted that ball <NUM> is used broadly to refer to an item able to block flow along internal passage <NUM>; and ball <NUM> may have a variety of shapes and configurations, e.g. partial balls, darts, and various other plugs.

After the ball <NUM> is seated against corresponding ball seat <NUM>, pressure may be increased along inner pressure region <NUM> to establish a pressure differential (delta P) between the inner pressure region <NUM> and the intermediate pressure region <NUM>. The increased pressure within inner pressure region <NUM> acts against module piston <NUM> via passages <NUM>. Upon sufficiently increased pressure, the module piston <NUM> is shifted linearly (to the right in the example illustrated in <FIG> and <FIG>) which, in turn, shifts upper sleeve <NUM> away from the corresponding dogs <NUM> so as to release the dogs <NUM> as illustrated in <FIG>.

Simultaneously, the increased pressure within pressure region <NUM> is able to act against the appropriate corresponding cylinder <NUM>, e.g. the upper cylinder <NUM>, via passages <NUM> and <NUM> (see <FIG>). Because the corresponding dogs <NUM> are no longer locking the lower hydraulic cylinder <NUM> in place relative to tubular structure <NUM>, sufficiently increased pressure is able to shift both cylinders <NUM> linearly along tubular structure <NUM>. The linear shifting of the cylinders <NUM> causes the liner hanger slips <NUM> to shift from a radially contracted position (see <FIG>) to a radially expanded configuration (see <FIG>) for gripping engagement with the surrounding casing <NUM>.

As illustrated in <FIG>, the interior of the corresponding cylinder <NUM> surrounding locking dogs <NUM> also may comprise relief recesses <NUM> which enable spring members <NUM> to once again bias the dogs <NUM> in a radial outward direction after actuation of the liner hanger <NUM>. This allows the dogs <NUM> to be shifted entirely out of the internal passage <NUM> to eliminate obstructions.

After setting the liner hanger <NUM>, continued application of pressure along internal passage <NUM> (or sufficiently increased pressure along internal passage <NUM>) enables shifting of CRT piston <NUM> so as to release collet <NUM>, thus releasing packer <NUM> and running string <NUM> (see <FIG>). Release of the packer <NUM> enables setting of the packer <NUM> via, for example, slacking off weight. Also, the running tool <NUM> and overall running string <NUM> may be withdrawn from the liner hanger assembly <NUM> and retrieved to the surface. In this example, dropping of ball <NUM> allows establishment of sufficient pressure differential(s) between inner pressure region <NUM> and intermediate pressure region <NUM> so as to enable sequential setting of liner hanger <NUM> and then release of packer <NUM> and running string <NUM>. Subsequently, the ball <NUM> and ball seat <NUM> may be removed from internal passage <NUM> by applying increased pressure to shear the ball seat <NUM> for removal. (However, other suitable mechanisms may be used to release the ball <NUM> and ball seat <NUM> from internal passage <NUM>.

Referring generally to <FIG>, another example of the liner hanger system <NUM> and its anti-preset module <NUM> is illustrated. In this embodiment, the anti-preset module <NUM> once again comprises locking mechanism <NUM> which may utilize a plurality of the locking dogs <NUM>. However, in this configuration the locking dogs <NUM> are positioned on running tool <NUM> for engagement with the corresponding hydraulic cylinder <NUM> through corresponding openings <NUM> formed through a liner hanger body <NUM> of liner hanger <NUM>.

Prior to setting of the liner hanger <NUM>, the locking dogs <NUM> are positioned in a radially extended configuration, through corresponding openings <NUM>, and into engagement with an interior of the corresponding cylinder <NUM>. By way of example, the interior of the corresponding cylinder <NUM> may have an abutment <NUM> which prevents linear movement of the corresponding cylinder <NUM> in an axial direction, e.g. in an upward direction, thus preventing premature actuation of liner hanger <NUM>.

According to the embodiment illustrated, the locking dogs <NUM> are held in radial openings <NUM> of a lock dog housing <NUM> and maintained in the radially outward, locked position by a lock dog support sleeve <NUM>. For example, the lock dog support sleeve <NUM> may comprise an enlarged diameter portion <NUM> which maintains the locking dogs <NUM> in the radially outward, locked position when portion <NUM> is located along the inner surface of the locking dogs <NUM>.

As illustrated, seals <NUM> may be positioned between liner hanger body <NUM> and corresponding cylinder <NUM> on both upper and lower sides of openings <NUM>. Similarly, seals <NUM> may be positioned between lock dog housing <NUM> and liner hanger body <NUM> on both upper and lower sides of radial openings <NUM>. Additionally, suitably located seals <NUM> may be positioned between lock dog support sleeve <NUM> and lock dog housing <NUM>.

While the anti-preset module <NUM> is in the run-in-hole position illustrated in <FIG>, a support sleeve port or ports <NUM> remain in alignment with corresponding port or ports <NUM> through lock dog housing <NUM>. The aligned ports <NUM> and <NUM> enable pressure equalization between inner pressure region <NUM> and intermediate pressure region <NUM> so as to avoid premature pressure differentials which could otherwise actuate the liner hanger <NUM>. Additionally, the locking dogs <NUM> prevent premature actuation. It should be noted that the anti-preset module <NUM> may comprise various other components and features, such as the dampening chambers <NUM> and <NUM> which can be arranged to dampen shifting of the components during actuation.

In <FIG>, a hanger setting configuration is illustrated. In this configuration, ball <NUM> has been dropped down through internal passage <NUM> and into engagement with ball seat <NUM>. By way of example, ball seat <NUM> may be a segmented ball seat releasably secured to lock dog support sleeve <NUM>.

To actuate the liner hanger <NUM>, the ball <NUM> is landed on ball seat <NUM> and pressure is increased in inner pressure region <NUM> relative to intermediate pressure region <NUM> until a first set of shear screws <NUM> is sheared. This allows the lock dog support sleeve <NUM> to shift relative to lock dog housing <NUM>, e.g. to move in a downwards direction or to the right in <FIG>. This movement of lock dog support sleeve <NUM> also shifts enlarged diameter portion <NUM> from under the locking dogs <NUM> so that locking dogs <NUM> may retract inwardly. The radially inward movement of locking dogs <NUM> releases them from the corresponding cylinder <NUM>. In some embodiments, magnets <NUM> or other biasing mechanisms may be used to help draw the locking dogs <NUM> in a radially inward direction.

At the same time, the support sleeve ports <NUM> are moved out of alignment with corresponding ports <NUM>; and seals <NUM> are positioned to straddle and isolate the corresponding pressure equalization ports <NUM>. It should be noted that a check valve <NUM> may be positioned in a corresponding passage extending generally radially through lock dog housing <NUM> to ensure there remains no trapped pressure in intermediate pressure region <NUM>, e.g. in the space between the running tool <NUM> and the liner hanger body <NUM>.

Once the corresponding ports <NUM> are isolated, the pressure applied along inner pressure region <NUM> is able to move through ports <NUM>, through radial openings <NUM>, and through corresponding openings <NUM> to shift the corresponding cylinder <NUM>, as illustrated in <FIG>. By continuing to increase the pressure along inner pressure region <NUM>, the running tool <NUM> may be released and a second set of shear screws <NUM> may be sheared to thus allow shifting of the segments of ball seat <NUM>, as illustrated in <FIG>. By way of example, the segments of ball seat <NUM> may be shifted into a suitable recess such as dampening chamber <NUM>. In some embodiments, the segments of ball seat <NUM> may include magnets <NUM> or other biasing mechanisms to help ensure the segments remain in dampening chamber <NUM>. After removal of the running tool <NUM>, additional operations, e.g. cementing operations, may be performed.

It should be noted the liner hanger assembly <NUM> and running string <NUM> may be constructed in various sizes and configurations. Additionally, each of these components of the overall liner hanger system <NUM> may utilize various engagement features, seals, flow port arrangements, flow passages, and/or other features to enable the desired operation. For example, various flow passage arrangements may be used to achieve the desired equalization of pressures between the inner pressure chamber and the intermediate pressure chamber. Additionally, various types of balls may be used or other types of mechanisms may be used to enable selective achievement of the pressure differentials for releasing the anti-preset module, for actuating the liner hanger, and/or for releasing the running tool.

Claim 1:
A system for use in a well, comprising:
running string (<NUM>) comprising a running tool (<NUM>);
a liner hanger assembly (<NUM>) coupled with the running tool (<NUM>) for conveyance to a desired location in a borehole, the liner hanger assembly comprising:
a packer (<NUM>);
a liner hanger (<NUM>) actuatable between a radially contracted position and a radially expanded set position by applying a sufficient pressure differential between an inner pressure region (<NUM>) and an intermediate pressure region (<NUM>); and
a ball seat (<NUM>) positioned to receive a ball blocking communication between the inner pressure region and the intermediate pressure region to enable application of the sufficient pressure differential;
characterised in that the system comprises an anti-preset module (<NUM>) comprising a locking mechanism (<NUM>) mounted on the liner hanger assembly (<NUM>) and a sleeve (<NUM>) mounted in the running tool, wherein the locking mechanism comprises a plurality of dogs held in in a radially outward locked position by the sleeve (<NUM>) to lock the liner hanger (<NUM>) against actuation, the sleeve (<NUM>) being shiftable to release the locking dogs (<NUM>) in response to buildup of the sufficient pressure differential.