ABSTRACT: Exploring for Carbonate-Hosted Gas Fields Affected by Thermochemical Sulfate Reduction and Hydrothermal Dolomitization (TSR-HTD), with Examples from Northeastern British Columbia, Canada

REIMER, JAMES D., MARK R. TEARE, and B. DOUG BEARINGER, Home Oil Company Ltd., Calgary, Alberta, Canada

Thermochemical sulfate reduction and hydrothermal dolomitization (TSR-HTD) is a diagenetic process that created and modified many carbonate-hosted gas fields, including various Paleozoic pools in northeastern British Columbia, Canada. In this TSR-HTD process, oil-bearing limestone is converted into gas-charged dolomite through the application of heat during continued burial. The resulting rock fabrics, which include brecciation, pinpoint to cavernous porosity, intense microfracturing, plus variable replacement and occluding saddle dolomitization, have led us to propose a furnace architecture model to describe this process. The furnace produces an anisotropic and inhomogenous reservoir, which has important implications for exploration.

In particular, we recognize four key manifestations. (1) TSR-HTD may affect platform interior as well as bank edge or embayment reef facies. (2) Variably shaped collapse features, dolomite chimneys, and dolomite sills are produced by this process. (3) Wireline log response of TSR-HTD reservoirs includes evidence of fractures, sulfide mineralization, and borehole gas effects. (4) TSR-HTD reservoir pressure buildup behavior may indicate a combination of radial, linear, and bilinear flow geometries.

We have documented these features in many of the existing fields and believe that further application of the TSR-HTD concepts will lead Home Oil and its partners to develop additional discoveries in this and other gas provinces.

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