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Abstract: Redeveloping a Mature Niagaran Reef Using Horizontal Well Technology: A Case History of Colfax 25 Field

Shell Noreast Co., Houston, TX

Horizontal wells in the northern Michigan Niagaran reef trend were first experimented with in 1987. Since then, numerous operators have drilled horizontal wells in an attempt to rejuvenate production from mature fields. Justifications for drilling lateral drainholes include reducing gas coning and water coning, and intersecting undrained portions of the reservoir. This presentation will show a case history of the Colfax 25 field, operated by Shell Western E&P (SWEPI), where horizontal drilling was used to redevelop the field. The Colfax 25 field was originally developed with 3 vertical wells in the mid-80s. Beginning in 1995, the three vertical wells were re-entered and drilled laterally, and two new wells were also drilled laterally within the field limits. This redevelopment resulted in increasing oil production from 600 BOPD in mid-1994 to 1500 BOPD in early 1996, and is expected to recover an additional 11% of the OOIP or 1.2 MMBO in incremental reserves. The redevelopment effort at Colfax 25 also provided us valuable insight into the lateral variations of overall rock quality within Niagaran pinnacle reefs. Conventional mud logs and pump down neutron logs (TDT) were used to evaluate the lateral drainholes. Observed porosities ranged from 3% to 30%+. As of early 1998, the field is producing 530 BOPD and 260 MCFGPD. Controlling the Gas Oil Ratio to maintain oil production continues to be our major focus of effort.

AAPG Search and Discovery Article #90930©1998 AAPG Eastern Section, Columbus, Ohio