Makarem-l Relief Well Planning and Drilling

Abstract

Abstract This case history describes planning and execution of a deep relief well operation that resulted in re-entering, killing and abandoning a wellbore which was blowing in the subsurface. In 1994, a gas exploration well, Makarem, was sidetracked past a bottomhole assembly, which had become stuck almost 1,000m off bottom. A kick was subsequently taken, indicating charging of shallower horizons from a deep, sour, high-pressure gas reservoir at potentially high rates. Attempts to reenter the original wellbore while drilling ahead in the sidetrack hole were unsuccessful. The well was re-entered in 1997 with the objective of isolating the flowing zone to prevent potential environmental impact, future drilling problems, and the loss of hydrocarbon reserves resulting from uncontrolled flow of gas in the subsurface. This case history reviews planning and execution of a deep horning-in operation to locate and re-enter the 12 1/4" open hole below the bit of the stuck assembly, 3680m below surface. Key issues addressed during the planning phase included relief well strategy, positional uncertainty, well control scenarios, options for isolation and contingencies. An active electro-magnetic ranging technique was employed to successfully locate and track the target assembly to an eventual direct intersection with the crossflowing hole. Execution of the intersection plan is detailed, with emphasis on horning-in on the fish, borehole surveying techniques and quality assurance. Also covered is the operational organisation, and details of the activities following intersection, which included stabilisation, cleanout and abandonment of almost 1,000m of borehole which had been inaccessible for over 3 years. P. 367