The Value of Rotary Closed - Loop Drilling Technology on Chevron Alba's North Sea Horizontal Field Development

Abstract

Abstract This paper describes how innovative Rotary Closed – Loop Steerable (RCLS) drilling technology was introduced to the Chevron Alba field in an effort to optimize horizontal well placement and extend the production life of the field. The application of the RCLS technology has been more successful than initially anticipated, with significant well cost reductions being realised. Moreover, it has allowed access to targets that could not be reached using conventional technology, thereby increasing ultimate recovery from the Alba field. Initial field development utilized conventional steerable drilling technology, i.e. motor assemblies and rotary drilling assemblies with adjustable stabilizers. Due to geological uncertainties, directional well plans routinely featured pilot holes with an option for one or more geological sidetracks. However, the well designs were constrained by the limitations of the conventional technology. Specifically, the limited ability to steer in the unconsolidated reservoir sands set limits on the dogleg capability and therefore lowered target TVD objectives. Drilling efficiency was compromised too; non-aggressive tri - cone bits were used in preference to PDC bits to facilitate directional control and consequently this limited BHA run length. In the late 90's a reassessment of the seismic data for the Alba field established new target areas for which it would be necessary to drill more esoteric well designs. This paper outlines the rotary drilling strategy adopted by the Alba project team to accomplish that objective. A review is made of the drilling risks on Alba in the 12 ¼" and 8 ½" hole sections from the conventional drilling perspective, and how these risks became more manageable through improvements in drilling performance with RCLS. In conclusion, an assessment of the technical and financial impact that RCLS technology made on drilling operations on the Alba platform is presented.