| Dolomitization of Leduc Formation (Upper Devonian) along the southern part of the Rimbey-Meadowbrook trend in central Alberta occurred early by pervasive replacement, and later by minor cementation. Replacive dolomitization postdates submarine cementation and deposition of overlying shales, overlaps stylolitization, and produces ;The distribution of pore types is governed by depositional facies, whereas effective porosity and permeability are strongly controlled by post-depositional processes. Late-stage cementation (anhydrite, dolomite, calcite, and native sulphur) reduces porosity. This cementation decreases northward, resulting in better reservoirs north of the Medicine River field, above present depths of 3000 m. Replacement dolomitization modified original pore type distribution, improved permeability, and helped retain porosity because dolomites are more resistant to pressure solution than limestones. Burial dissolution of dolomites may have been induced by mixing corrosion, maturation of organic matter, and thermochemical sulphate reduction. |
