WorldOil

Alternative well control methods for deepwater dual density drilling

Deepwater resources are expected to be a major contributor to future oil and gas production worldwide. Deepwater Gulf of Mexico resources are especially important for suppressing US production decline. However, a narrow margin between formation pore pressure and Fracture Pressure (FP) exists in many over-pressured basins, including the GOM. This limited margin often becomes narrower with increasing water depth due to reduced overburden pressure and shallow abnormal pressure. For deepwater wells, reaching the target depth, while retaining a useable borehole size, is often difficult. Deepwater resource development is often limited by high capital costs. Dual-gradient drilling methods have been proposed to retain a useable borehole size and provide simpler, safer, more economicwell designs that could increase deepwater gas development and use. The authors studied a dual density drilling concept using riser gas-lift to implement a dual-gradient system.