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Abstract The Middle Triassic Halfway formation in northeastern British Columbia is a high quality, well sorted quartzose sublitharenite. Past drilling operations using conventional overbalanced technology in the reservoir had indicated significant formation damage occurred due to a combination of mechanical and chemical formation damage effects associated with the loss of drilling fluid to the formation. A series of compatibility and special core analysis tests were conducted to refine an underbalanced drilling procedure with natural gas for a 300 m long horizontal well in the formation using a natural gas-mist hydrocarbon system at a 1400 kPa underbalance pressure level. The well was drilled successfully and flowed at peak rates of up to 1100 m3/day (almost 7000 bbl/day) of oil and 340,000 m3/day (12,000,000 scf/day) of gas during the underbalanced drilling operation. Post test pressure transient and interference tests indicated an in-situ permeability of 150 mD with zero skin factor indicating that the well had been drilled successfully in an undamaged fashion. The well has currently produced close to 13,000 m3 of oil (80,000 bbl) and over 11,000,000 m3 (400 MMscf) of gas with initial AOF potential of approximately 520 m3/day (3300 bbl/day).
Doane et al. (Mon,) studied this question.