Wellbore pressure management is a critical part of the drilling process. In normal drilling practices, static and dynamic fluid pressures are used to contain formation pressures and to 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 Equivalent Circulation Density (ECD) Reduction Tool (RT) has been developed.
The ECD RT is designed to counter the frictional pressure effects that exist while circulating. The tool is expected to have a broad range of drilling applications including; the narrow pore/fracture pressure margin deepwater environment, wellbores prone to instability, pressure depleted reservoirs, and extended reach wells.
The tool has the potential to:
Improve wellbore stability
Extend hole intervals and reduce casing requirements
Improve well control
Reduce lost circulation
Reduce differential sticking
Improve hole cleaning in ERD wells through the use of higher flow rates
This paper describes a new downhole tool for ECD reduction, which is run as an integral part of the drill string. A prototype tool has been built to operate inside 10c3/4″ to 13−3/8″ casing. This tool has undergone laboratory testing and full-scale technology trials are in progress. The design features of this prototype are discussed along with the laboratory test results obtained to date.