Downhole plug holder and method

A plug holder sub for being supported on a conveyance tubular for temporarily supporting a wiper plug and for releasing the wiper plug in response to an increase in fluid pressure within the conveyance tubular, the plug holder sub comprising:

• a generally tubular body adapted for connection with the conveyance tubular and having a throughbore in fluid communication with the conveyance tubular;
• a retainer member for attaching the liner wiper plug to the tubular body, the retainer member movable from a retaining position to a release position for releasing the wiper plug from the tubular body;
• a piston axially movable within the tubular body in response to fluid pressure within the throughbore for preventing the retainer member from moving to the release position, a radially interior surface of the piston engaging the retainer member to prevent the retainer member from moving to the release position, and axial movement of the piston releases the retainer member to the release position, the piston acting against a fluid within a chamber within the tubular body when moving to the release position;
• and
• a metering jet along a fluid flow path from the fluid chamber to an annulus about the tubular body, such the fluid pressure within the throughbore restrains movement of the piston to the release position until fluid is forced through the metering jet, thereby preventing release of the wiper plug until the piston moves to the release position.

A method of supporting a liner wiper plug on a conveyance tubular and for releasing the liner wiper plug in response to an increase in fluid pressure within the conveyance tubular, the method comprising:

• providing a generally tubular body adapted for connection with the conveyance tubular and having a throughbore in fluid communication with the conveyance tubular;
• providing a retainer member for attaching the liner wiper plug to the tubular body, the retainer member movable from a retaining position to a release position for releasing the liner wiper plug from the tubular body;
• moving a piston within the tubular body in response to fluid pressure within the throughbore for preventing the retainer member from moving to the release position, the piston acting against a fluid within a chamber within the tubular body when moving to the release position;
• metering discharge of fluid along a fluid flow path from the fluid chamber to an annulus about the tubular body, such that fluid pressure within the throughbore restrains movement of the piston to the release position until fluid is forced through a metering jet, thereby preventing release of the liner wiper plug until the piston moves to the release position;
• allowing the retainer member to move to the release position when the piston is in the release position, thereby releasing the liner wiper plug from the tubular body;
• and monitoring a drop in fluid pressure in response to the release of the liner wiper plug.

A liner hanger running tool for running the liner into a well from a running string, the liner hanger running tool including a plug holder sub to support a liner wiper plug on the running tool, such that a pump down plug lands on the liner wiper plug to substantially limit flow through the running tool, the running tool further comprising:

• the plug holder sub being secured to a running tool mandrel;
• a fluid filled chamber within the plug holder sub, such that the chamber is vented to outside the plug holder sub through a restricted orifice;
• a fluid pressure responsive piston moveable within the chamber relative to the plug holder sub from a locked position wherein the liner wiper plug is supported from the plug holder sub to a release position wherein the liner wiper plug is released from the plug holder sub;
• and
• a radially expandable lock ring for gripping engagement with the liner wiper plug, such that radially outward movement of the lock ring in response to movement of the piston releases the liner wiper plug from the plug holder sub.