BACKGROUND

This disclosure relates generally to methods and apparatus for expanding a tubular in a wellbore.

In known expandable systems, the expandable tubular is provided with a shoe or plug at the bottom. The shoe or plug is provided to seal a lower portion of the expandable tubular so that fluid pressure can be increased in the lower portion. The fluid pressure is, in turn, utilized to assist an expansion system with the vertical movement of an expansion cone along the length of the expandable tubular. After the expansion of the expandable tubular, operators drill out the shoe in a separate trip. The drill out of the shoe often generates debris into the wellbore.

In other known expandable systems, the expandable tubular can be shoeless. The expansion of the expandable tubular may rely on a jack-style actuator used repeatedly to expand portions of the expandable tubular sequentially, for example, as shown in U.S. Pat. No. 7,240,729. However, with these expansion systems, it can be difficult to lock the jack-style actuator on the usually smooth bore of the expandable tubular.

There is a continuing need in the art for methods and apparatus for expanding a tubular in a wellbore that are capable of expanding a shoeless tubular.

BRIEF SUMMARY OF THE DISCLOSURE

The disclosure describes an expansion system that may be used for expanding an expandable tubular. The expandable tubular may not have a shoe or plug.

The expansion system may comprise an operational pipe. The operational pipe may include a plurality of sections. The operational pipe may include a releasable latch located at the bottom of the operational pipe and coupled to the expandable tubular. The operational pipe may include a cap. The cap may have a shoulder.

The expansion system may comprise an actuator. The actuator may be modular. The actuator may include a plurality of stages. The actuator may include a bottom shoulder capable of catching the shoulder of the cap.

The expansion system may comprise a mandrel and cone assembly. The mandrel and cone assembly may include a plurality of extensions. The mandrel and cone assembly may include enlarged portions or buckling arrestors on each of the plurality of extensions. The enlarged portions or buckling arrestors may be sized to extend the releasable latch radially and prevent the releasable latch from decoupling from the expandable tubular. The mandrel and cone assembly may include an unsupported section above a cone. The unsupported section may be sized to allow the releasable latch to contract radially and decouple from the expandable tubular.

The expansion system may comprise a unidirectional locking mechanism. The unidirectional locking mechanism may be stationary relative to one of the actuator or the operational pipe and unidirectionally movable relative to the other of the actuator and the operational pipe. For example, the unidirectional locking mechanism includes a split-ring ratcheting lock configured to releasably engage and unidirectionally lock to inner threads on the plurality of sections of the operational pipe. Alternatively, the unidirectional locking mechanism includes a split-ring ratcheting lock configured to releasably engage and unidirectionally lock to outer threads on a housing of the actuator or extension collars mounted on the actuator.

The disclosure also describes a method for expanding an expandable tubular.

The method may comprise the step of measuring a length an expandable tubular. The method may comprise the step of determining a first number of sections to form an operational pipe based on the measured length. The method may comprise the step of determining a second number of extensions to form a mandrel and cone assembly based on the measured length. The method may comprise the step of determining a force magnitude to expand the expandable tubular and a fluid pressure to expand the expandable tubular. The method may comprise the step of determining a third number of stages to achieve the force magnitude with the fluid pressure.

The method may comprise the step of assembling an expansion system as described hereinabove. For example, the expansion system may include an operational pipe formed with the first number of sections, a mandrel and cone assembly formed with the second number of extensions, an actuator formed with the third number of stages, and a unidirectional locking mechanism.

The method may comprise the step of expanding the expandable tubular. Expanding the expandable tubular may comprise the repeated steps of stroking the actuator. For example, the unidirectional locking mechanism may be engaged to the operational pipe during a stroke of the actuator; and the unidirectional locking mechanism may move relative to the operational pipe during a reverse stroke of the actuator. Expanding the expandable tubular may further comprise extending a releasable latch with enlarged portions or buckling arrestors to prevent the releasable latch from decoupling from the expandable tubular.

The method may comprise the step of contracting the releasable latch within an unsupported section to allow the releasable latch to decouple from the expandable tubular. The method may comprise the step of catching a cap of the operational member with a bottom shoulder of the actuator to hang the operational pipe from the actuator.

