The cement goes between the outside of the casing and the well bore.

FORBES: The Fracking Solution Is A Good Cement Job

Then there is Halliburton, which was contracted to cement the production liner in the well casing, effectively sealing off the reservoir from the well bore.

FORBES

Halliburton ( HAL - news - people ), which was contracted to cement the production liner in the well casing, effectively sealing off the reservoir from the well bore.

FORBES: The Gulf Oil Leak