High equivalent circulation density (ECD) is responsible for many wellbore pressure-related problems during drilling. Proper wellbore pressure management is a critical part of normal drilling practices, where static and dynamic fluid pressures are used to contain formation pressures and assure wellbore stability. Excessive fluid pressure while circulating can create problems including reduced operating margins between fracture and pore pressures and, in the extreme, lost circulation. To address these problems, an ECD Reduction Tool (ECD RT) is being developed.
The ECD RT is designed to counter downhole pressure increase due to friction in the annulus by reducing the hydrostatic head. The tool is expected to have a broad range of drilling applications including the narrow pore/fracture pressure margin in the deepwater environment, wellbores prone to instability, pressure depleted reservoirs and extended reach wells. The ECD RT will also potentially reduce the impact of uncertainty when selecting casing setting depth by widening the usable margin between pore pressure and fracture gradient.