The oil company contacted us, and plans were made to re-enter the well and log casing for cement bond. Complications with milling the cement plug included the risk of gas migration through the 4-1/2" liner (up to 6,000 psi), creating a piston effect buckling and ejecting tubing while milling with 360,000 lbs of lift under the plug. Other complications arose from the suspected gas-bearing zone being sour.
Together, we engineered a solution of rigging up a 285k jack with a full 11" stack; RIH with 8-1/2" tri-cone bit and 3-1/2" IF drill pipe. We milled cement while holding 21 MPa on the annulus with two choke manifolds and a P-tank. If a kick was encountered, the gas cap could be bled off to continue milling to the liner top packer. POOH and RIH with 3 5/8" bit, six drill collars and 3-1/2" string to mill cement out of the liner. POOH and RIH with 3-5/8" bit, drift string mill, and L-80 tubing was cleaned down to the 2,400 m plug-back.