Sedimentology, sequence stratigraphy, and diagenesis of the Lower Cretaceous Viking formation, Dodsland and Hoosier area, west-central Saskatchewan.

摘要

The objectives of the thesis are to integrate detailed petrographic and diagenetic analyses within a sequence stratigraphic framework of the Viking sandstones at the Dodsland and Hoosier fields, west-central Saskatchewan and identify the effects of sea level fluctuation on reservoir properties. The study area includes townships 28 to 34 and ranges 17 to 28 west of the third meridian inclusive. In total, 36 core were analyzed in detail and 155 samples collected. Eighty-eight samples were prepared for petrographic analysis while stable isotope analysis was carried out on 44 samples.;Sandstones are classified as litharenties or lithic wackes. Porosity is characterized by enhanced primary intergranular porosity and secondary intragranular porosity developed through dissolution of framework grains. Destruction of porosity occurs during early compaction but decreases in magnitude as shown by the preservation of porosity in lithic sandstones. Precipitation of siderite and calcite cement is localized near the top portions of parasequences. delta 18O values for siderite and calcite cement (-4.0 to -8.8‰ VPDB and -13.6 to -8.0‰ VPDB respectively) indicate 18O is depleted with respect to normal marine water. delta13C values for siderite and calcite cement (-13.6 to -3.3‰ VPDB and -6.0 to 3.3‰ VPDB respectively) are also slightly depleted with respect to normal marine water. The slightly heavy delta130 value for calcite cement suggests decomposition of organic matter by methanogenic bacteria. These values are interpreted to be in response to meteoric water influx during relative sea level lows.;Eight unique fades indicate the Viking Formation was deposited in a distal upper offshore to lower shoreface environment. Three kinds of sequence stratigraphic surfaces are identified in the study area: sequence boundaries, transgressive surfaces, and marine flooding surfaces. Six sandying upwards, progradational parasequences reflect a lowstand systems tract. The apparent south imbricate geometry of the parasequences reflects southerly longshore currents. The oblique-to-normal shoreline of the Viking Formation at the Dodsland and Hoosier fields is related to the underlying east striking structural low where increased accommodation space encourages sediments to settle out of suspension.