Systems and methods for sealing a wellbore are provided. The system is for sealing a wellbore having a pipe therein for the passage of fluid therethrough. The system is provided with a BOP positionable about the pipe and at least one seal assembly positionable about the BOP. Each of the seal assemblies comprises a plurality of blocks positionable within the BOP, at least one actuator for selectively moving the blocks to a contact position surrounding the pipe and a plurality of pipe seals for creating a seal about the pipe. The seals are carried by the plurality of blocks. At least one of the pipe seals in each block is selectively extendable therefrom for sealing engagement about the pipe after the blocks are moved to the contact position whereby the pipe seals are prevented from extending between the blocks as the blocks are moved to the contact position.