Technique for borehole string running in Well A9 of one oilfield in Weizhou

Well A9 in Weizhou is a highly deviated production well in the Beibu Gulf of Beihai, Guangxi province. It was completed by running ?178 mm string in openhole. Well A9 was characterized by high pressure coefficient of target zone, high drilling fluid density, great viscosity and shearing force, large dogleg, large hole inclination angle, long horizontal section and the target zones being mostly large sections of mudstone and shale. Comprehensive analysis shows that the major difficulties in completion technique include great friction when borehole string is run, difficulty in well control and reservoir protection, high surging pressure and circulation pressure during tripping in which may cause the suspension packer to set midway. In view of the above difficulties, analysis was conducted to the difficulties in running borehole string, the string running friction was calculated and the pipe string configuration was optimized. The drilling and completion fluid systems which could protect the reservoir and the suspension packer assembly with special structure were used, hence the pipe string was run smoothly and satisfactory oil well production was obtained. This technique provides a reference for the running of borehole string and tripping jobs under similar complex downhole conditions.