--> Abstract: Fractures of a Triassic Carbonate Reservoir in Northeastern British Columbia, Canada, by T. Joubert and C. Rice; #90942 (1997).

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Abstract: Fractures of a Triassic Carbonate Reservoir in Northeastern British Columbia, Canada

JOUBERT, TERRY and Craig Rice

The upper Triassic trend of northeastern British Columbia, Canada, is a new and active gas exploration region. Gas production is from large amplitude, foreland verging, folded carbonates of the Pardonet and Baldonnel Formations. The main reservoir is the Baldonnel Formation, a low-grade dolomite with an average matrix porosity of 4-6% and non-fractured permeability often less than 0.5mD. Structural fractures enhance permeability two orders of magnitude or more. AOF rates are typically 50 - 75 Mmcf/day and as high as 223 Mmcf/day. Economic production rates and reserves are directly dependent on wells intersecting the fracture system. FMI logs from nine wells were interpreted to characterize the fractures. Four fracture orientations are at high angles to bedding. Two fracture set orientations are as oblique type 1 and type 2 fractures (StearnAs classification). Additionally, there are two orthogonal fracture sets that do not fit StearnAs classification. These fracture trend north/south and east/west and are likely pre-structural, regional fractures. Generally, large aperture fractures are in the outer layers of the fold, in non-reservoir rock units of the Pardonet Formation. Production profile logs show gas flow from thin discrete fracture zones in these layers, from type 2 and orthogonal orientations. Production data and the lack of pressure compartmentalization suggest that the fracture system must connect and drain the underlying reservoir units of the Baldonnel Formation. The data suggest that highly deviated directional drilling be oblique to structural trends, thus, maximizing the number of large aperture fractures intersected by the well bore.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria