A wellbore is plugged using a bismuth alloy. In one embodiment, the bismuth alloy comprises an alloy of bismuth and tin. In another embodiment, the bismuth alloy comprises an alloy of bismuth and silver. The wellbore can be arranged so that a liquid bismuth alloy sets with an excess pressure of the plug relative to the borehole fluid pressure along a desired seal height distance. Other aspects are described and claimed.

A wellbore is plugged using a bismuth alloy. In one embodiment, the bismuth alloy comprises an alloy of bismuth and tin. In another embodiment, the bismuth alloy comprises an alloy of bismuth and silver. The wellbore can be arranged so that a liquid bismuth alloy sets with an excess pressure of the plug relative to the borehole fluid pressure along a desired seal height distance. Other aspects are described and claimed.

The present concept is a method of removing casings from a well in the oil industry, which may be used for slot recovery. The method involves running an internal cutter down the production casing to cut through a preselected number of existing casings at one or more predetermined depths before drilling around the outermost preselected casing with a hollow drill bit. The hollow drill bit drills through the preselected outermost casing cement to the predetermined depth before a removal tool is used to remove the existing casings to the predetermined depth. These steps may be repeated using appropriately sized hollow drill bits and casings to drill around the next preselected outermost casings to the next predetermined depth, continuously removing the existing casings until all desired existing casings are removed.

The present concept is a method of removing casings from a well in the oil industry, which may be used for slot recovery. The method involves running an internal cutter down the production casing to cut through a preselected number of existing casings at one or more predetermined depths before drilling around the outermost preselected casing with a hollow drill bit. The hollow drill bit drills through the preselected outermost casing cement to the predetermined depth before a removal tool is used to remove the existing casings to the predetermined depth. These steps may be repeated using appropriately sized hollow drill bits and casings to drill around the next preselected outermost casings to the next predetermined depth, continuously removing the existing casings until all desired existing casings are removed.

A control system for controlling disconnection of riser system that extends between a vessel and a subsea location that comprises a wellbore, the riser system configured to receive a string in use, the control system being configured to disconnect the riser system according to a sequence of operations, the sequence of operations comprising disconnecting the riser system prior to or simultaneous with cutting the string and sealing the well bore.

The present concept is a method of slot recovery for the oil industry. The method involves running an internal cutter down the production casing to cut through a preselected number of existing casings at predetermined depths before drilling around the outermost preselected casing with a hollow drill bit. The hollow drill bit drills through the preslected outermost casing cement to the predetermined depth before a removal tool attached to the inside of the production casing is used to remove the existing casings to the predetermined depth. These steps are repeated using appropriately sized hollow drill bits and casings to drill around the next preselected outermost casings to the next predetermined depth, continuously removing the existing casings until all desired existing casings are removed.

The present concept is a method of slot recovery for the oil industry. The method involves running an internal cutter down the production casing to cut through a preselected number of existing casings at predetermined depths before drilling around the outermost preselected casing with a hollow drill bit. The hollow drill bit drills through the preslected outermost casing cement to the predetermined depth before a removal tool attached to the inside of the production casing is used to remove the existing casings to the predetermined depth. These steps are repeated using appropriately sized hollow drill bits and casings to drill around the next preselected outermost casings to the next predetermined depth, continuously removing the existing casings until all desired existing casings are removed.

The present invention provides an improved hydraulically activated clamping device for connecting a wellhead and or Christmas tree positioned on a wellhead to a fracing tree that may comprise a connector body; a mandrel body; two or more clamp segments; two or more actuating bolts; a seal ring to provide sealing engagement between said connector body and said mandrel body; one or more motors driving each of said two or more actuating bolts; and control means to reduce or retard the power to the first of said two or more actuating bolts to release and prevent its further movement until the other of said actuating bolts release also.

The present invention provides an improved hydraulically activated clamping device for connecting a wellhead and or Christmas tree positioned on a wellhead to a fracing tree that may comprise a connector body; a mandrel body; two or more clamp segments; two or more actuating bolts; a seal ring to provide sealing engagement between said connector body and said mandrel body; one or more motors driving each of said two or more actuating bolts; and control means to reduce or retard the power to the first of said two or more actuating bolts to release and prevent its further movement until the other of said actuating bolts release also.

The present invention provides an improved hydraulically activated clamping device for connecting a wellhead and or Christmas tree positioned on a wellhead to a fracing tree that may comprise a connector body; a mandrel body; two or more clamp segments; two or more actuating bolts; a seal ring to provide sealing engagement between said connector body and said mandrel body; one or more motors driving each of said two or more actuating bolts; and control means to reduce or retard the power to the first of said two or more actuating bolts to release and prevent its further movement until the other of said actuating bolts release also.