Coiled-Tubing Drilling of Horizontal Sidetrack in House Mountain Field, Alberta

Abstract

Summary In 1995, the first horizontal sidetrack successfully drilled using coiled tubing (CT) was carried out at Shell's House Mountain oilfield. The objective was to drill underbalanced a 378-in. diam by 300-m-long horizontal hole section from an existing vertical, cased oil well. The existing well was re-entered using a conventional drilling rig; a window milled in the casing, and the build section drilled to an inclination of 90°. 238-in. CT was then used to directionally drill the horizontal section underbalanced with nitrified water. The zone of interest was a Devonian-age reef-edge and limestone structure, at a depth of about 2200 m, called the Slave Point. A case history of directionally drilling the horizontal sidetrack using 238-in. OD. CT is provided. Coiled-tubing drilling proved to be a cost-effective alternative to drilling the horizontal sidetrack without using a conventional drilling rig. Shorter trip times, underbalanced drilling, enhanced rates of penetration (ROP), and the ability to maintain weight on bit were all achieved. ROPs increased by up to three-fold while drilling underbalanced.