ABSTRACT: Hydrocarbon Exploration in the Debolt Formation, Northeastern British Columbia, Canada

MAJID, A. HAMID, Canadian International Petroleum Consultants Ltd., Calgary, Alberta, Canada, and GRAHAM DAVIES, Graham Davies Geological Consultants Ltd., Calgary, Alberta, Canada

Utilizing all available log and core data, the Mississippian Debolt Formation in northeastern British Columbia has been subdivided into four regionally correlative members. From the top down, these are the Opal, Loomis, Salter-Baril-Wileman, and Turner Valley members.

The Debolt Formation in northeastern British Columbia is host to several play types. Two major types are (1) a hydrothermal dolomite gas play typified by the Sikanni field, and (2) an unconformity-bounded oil play exemplified by the Blueberry field. In the Sikanni-Grassy area, narrow, structurally controlled zones of fractured and vuggy saddle dolomite with internal solution-residue sediments occur within limestone hosts that show peripheral replacement by saddle dolomite crystals, a process designated as "saddlerization." Trapping is formed by Late Cretaceous-early Tertiary structures.

Dolomitization in the Blueberry-Halfway area is pervasive and unconformity-related. Erosional removal of the tighter Opal member of the Debolt allowed the underlying Loomis member to be exposed at an intra-Mississippian to Permian unconformity. Subsequent Late Cretaceous-early Tertiary thrust faulting and folding provided the trapping mechanism. Other potentially important play types include porosity fairways in dolomite controlled by normal fault conduits, and thrust-controlled anticlinal rollover traps in porous or fractured limestone or dolomite.

The Debolt in northeastern British Columbia continues to have high gas potential. The Sikanni-Grassy-Pocketknife trend, and its possible northern extensions, remain the areas of most interest.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)