THE PRIMARY SEALING UNITS FOR THE WEYBURN MIDALE RESERVOIR, WILLISTON BASIN, (SOUTHEASTERN SASKATCHEWAN, CANADA): SEDIMENTOLOGY, PETROGRAPHY, AND GEOCHEMISTRY

摘要

The Weyburn Midale reservoir, in southeastern Saskatchewan, is a Mississippian hydrocarbon reservoir that is under study for the purpose of CO_2 sequestration. The sealing units for this reservoir are therefore important to characterize, as they represent the primary barriers to CO_2 migration.rnThree units represent the main seals for the reservoir rock: 1) the overlying Midale Evaporite, a subaqueously-deposited salina-type anhydrite bed, 2) the underlying Frobisher evaporite, an arcuate sabkha-deposited anhydrite bed, and 3) an up-dip "altered zone" which is a diagenetic zone of porosity destruction near a regional unconformity.rnTogether, the sedimentological, petrographical, and geochemical natures of these three sealing units show that they are effective barriers to the migration of CO_2 in the long-term.