The operator’s concerns
Sustained casing pressure occurs in 71% of Dragon Oil' wells in its largest production oil asset field largely because of insufficient isolation across a gas zone with a narrow pore-to-fracture pressure window and high risk of lost circulation.
Why the problem was challenging
Enhanced cement placement techniques and industry best practices failed to solve the problem. In a few cases, SCP was seen immediately after cementing with high losses that prevented the top of cement from reaching the goal depth. More often, however, the problem was not related to cement placement but rather the inability of the cement to withstand downhole stresses from perforating, stimulation, and production.
What Schlumberger recommended
Engineers used CEMENTICS zonal isolation software to optimize a lead-tail cement system with a gas-tight conventional slurry covering the gas-bearing formations and CemFIT Heal system acting as a flexible, self-healing secondary barrier covering at least 450 m.