Underbalanced Coiled-Tubing-Drilled Horizontal Well in the North Sea

摘要

Maersk Olie & Gas A/S (Maersk Oil) has drilled a 3,309-ft-long near-horizontal drainhole with coiled tubing to a total measured depth (MD) of 11,000 ft in the Danish sector of the North Sea. The well was completed in May 1994 as a 3(1/2)-in. openhole producer in the Gorm field chalk reservoir. Part of the well was drilled at underba-lanced conditions, and oil production rates of up to 1,100 STB/D were reached during drilling. Conventional well-test equipment was used for handling returns. A nearby process facilities platform supplied lift gas and received the produced hydrocarbons during the drilling phase. Worth noting are the penetration of several chert layers, the fairly long reach, and the application of geosteering. Indications were that the well productivity was significantly improved compared with that of a conventionally drilled well, but problems were experienced with borehole stability in a fractured region.