Main bore isolation assembly for multi-lateral use

A wellbore isolation device for use in lateral completions, comprising:

• a whipstock;
• a support assembly to sealingly support the whipstock in a well-bore for forming at least one lateral;
• a valve member selectively operable between a closed position wherein flow past said support assembly is substantially shut off and an open position where flow past said support assembly can occur;
• said valve member comprises a sliding sleeve which exposes a port for flow around said whipstock;
• said valve member is actuated by a tool which washes over said whipstock without damaging it so that said tool can apply a moving force to said sleeve.

A method of forming a lateral in a wellbore wall, comprising:

• providing an isolation device against the wellbore wall;
• running in a whipstock with a valve assembly to said isolation device;
• forming a lateral through the wellbore wall with a portion of the wellbore isolated at a point below said whipstock due to, at least in part, said valve assembly being in the closed position;
• opening said valve assembly to provide flow access from below said whipstock with said whipstock in place.

A method of forming a lateral in a wellbore, comprising:

• providing an isolation device in the wellbore;
• running in a whipstock with a valve assembly to said isolation device;
• forming a lateral with a portion of the wellbore isolated at a point below said whipstock due to, at least in part, said valve assembly being in the closed position;
• opening said valve assembly to provide flow access from below said whipstock with said whipstock in place;
• providing an equalization sub adjacent one of said valve assembly and whipstock to allow stabbing into said isolation device without fluid lock.

A method of forming a lateral in a wellbore, comprising:

• providing an isolation device in the wellbore;
• running in a whipstock with a valve assembly to said isolation device;
• forming a lateral with a portion of the wellbore isolated at a point below said whipstock due to, at least in part, said valve assembly being in the closed position;
• opening said valve assembly to provide flow access from below said whipstock with said whipstock in place;
• using a sliding sleeve as the valve assembly;
• providing a debris barrier adjacent said sleeve.

A method of forming a lateral in a wellbore, comprising:

• providing an isolation device in the wellbore;
• running in a whipstock with a valve assembly to said isolation device;
• forming a lateral with a portion of the wellbore isolated at a point below said whipstock due to, at least in part, said valve assembly being in the closed position;
• opening said valve assembly to provide flow access from below said whipstock with said whipstock in place;
• using a sliding sleeve as the valve assembly
• using a tool to wash over said whipstock to apply a force to shift said sleeve.