The Use of Coiled Tubing During the Wytch Farm Extended Reach Drilling Project

Abstract

Abstract The largest onshore oilfield in Western Europe is situated in an environmentally sensitive coastal area on the south coast of England. Initial development of the field in the late 1970's focused on accessing reserves underlying the onshore section of the reservoir. In 1989, various development options were screened to access the offshore section of the reservoir, containing some 80 million barrels of recoverable oil. In 1991, the decision was made to access these reserves through extended reach drilling (ERD) from an existing onshore well-site. This development is currently underway, with three out of a planned eleven wells already drilled and producing. This paper will describe the application of Coiled Tubing in the logging and completion phases of the ERD wells drilled to date, including:-Operational details of Coiled Tubing deployed cement evaluation logging suites to a measured depth of 5,695m (18,685ft) at a horizontal departure of 4,950m (16,241ft), and a cased-hole vertical seismic profile to a measured depth of 4,391 m (14,330ft) at a horizontal departure of 3,800m (12,468ft).Operational details of Coiled Tubing use during the completion; setting/pulling plugs, shining sliding sleeves, sand/debris clean-outs, including novel tool and procedural developments.Results of predictive modelling to assess the point of helical lock-up, and comparisons of field data with these predictions.Details of operations involving the use of friction reduction chemicals to enhance Coiled Tubing penetration.The effects of ERD well tangent section angle on Coiled Tubing penetration. Conclusions are made as to the value of Coiled Tubing in ERD wells to minimise rig time and the current limits of technology. Introduction Wytch Farm is the largest onshore oilfield in Western Europe, and is situated on the southern coast of England, approximately 100 miles south west of London. The main reservoir lies under Poole Harbour, extending offshore under Poole Bay (Figure 1), and is in an Area of Outstanding Natural Beauty with Sites of Special Scientific Interest and Special Protection Areas, noted for its landscape, ecology and amenity value. The field was discovered in 1974, and the majority of production comes from two oil bearing sandstone formations.