Sedimentologic, stratigraphic, and diagenetic study of the Viking Formation, Bayhurst Pool and surrounding areas, southwestern Saskatchewan

The objectives of this thesis research are to understand how depositional facies are related to the reservoir architecture and what the regional stratigraphic relationship is between the Bayhurst Pool and the other Viking pools to the north and east, within southwest Saskatchewan. The detailed portion of the study area encompasses Townships 23 to 27 and Ranges 22 to 28W3 concentrating on the Bayhurst Pool. A regional study has been extended north and east from the detailed study area to include Townships 29 and Ranges 28W3, for a total area of about 3500 square miles. Core logging of 45 wells was completed and 59 samples were collected. Twenty-eight thin sections were studied for petrography, 11 samples were analyzed for O and C isotope analysis and 5 samples were studied for fluid inclusions.; Core and well log cross sections, together with sedimentary facies maps, illustrate the stratigraphy and reservoir architecture of the Bayhurst gas pool and surrounding area, defined by four distinct systems tracts, separated by flooding surfaces, unconformities, and ravinement surfaces. Fourteen distinct sedimentary facies were identified. The Bayhurst reservoirs consist of high porosity and permeability sandstones of a transgressively retrograding barrier island system, which unconformably overlies 'regional' coarsening upwards shoreface and shelf deposits. Viking oil and gas pools to the north and east are hosted in transgressively reworked lowstand shoreface deposits characterized by relatively low permeability and porosity. The reservoirs are capped by transgressive marine shales of the Westgate Formation.; Petrographic studies indicate Viking sandstones are characterized as sublitharenite, sublithic wacke, litharenite, lithic wacke and calcareous sublitharenite. Porosity values based on point counting range from 1% to 33%, with the highest values in the shoreface, incised valley fill and barrier island washover facies. Porosity is mostly primary although dissolution is locally significant. Cementation (quartz overgrowth and carbonates) is minor throughout, except at the top of the Viking Formation where massive calcite cement completely occludes the porosity. Fluid inclusions in calcite cements are all monophase (liquid-only), indicating early cementation at relatively low temperatures. Low delta18O values of calcite cement (-13.1 to -11.5‰ VPDB) are interpreted to indicate meteoric water involvement in early diagenesis, which is related to sea level fall and resulting subaerial exposure.