Lithofacies distribution and depositional environment in the Lower Cretaceous McMurray Formation, BlackGold Lease, northern Alberta: implications for geometry and distribution of oil sand reservoirs

摘要: Within BlackGold Lease located in northern Alberta, the Lower Cretaceous McMurray Formation contains most prolific bitumen reservoirs deposited fluvial to tidally-influenced estuarine environments. Based on core descriptions and wire-line log evaluation, this study reveals six lithofacies: cross-stratified sandstone mudstone-clast breccia (Lf1), sandstone-dominated IHS (Lf2), mudstone-dominated (Lf3), thinly interbedded mudstone (Lf4), laminated (Lf5), clean with (Lf6). To understand evolution of depositional environments vertical lateral associations lithofacies are examined using well cross-sections slice maps. During overall rise relative sea level, evolved through three stages deposition: early stage represents channels minor tidal influence, middle estuary well-developed meandering channels, late a drowning estuary. The potential channel sandstones lower point-bar deposits stage. stacked correlatable between wells, forming sheet-like bodies that align SW-NE direction parallel inferred orientation major systems. consist mainly base-of-channel deposits. migration, which is crucial horizontal design for production, from changes abandoned channel-fills deposits, shown maps, probably indicate point bar once migrated toward channel-fills. trend, dip some approximately estimated be southwestward or northwestward, oblique perpendicular orientation.