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8667153 
Journal Article 
Coiled-tubing drilling of horizontal sidetrack in House Mountain Field, Alberta 
Milligan, MR; Andreychuk, MT; Lunan, WB 
2000 
1 
SPE Drilling & Completion
ISSN: 1064-6671
EISSN: 1930-0204 
15 
2 
92-96 
WOS:000087747000003 
In 1995, the first horizontal sidetrack successfully drilled using coiled tubing (CT) was carried out at Shell"s House Mountain 7. oilfield. The objective was to drill underbalanced a 3 7/8-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 degrees. 2 3/8-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 2 3/8-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 an bit were all achieved. ROPs increased by up to three-fold while drilling underbalanced.