Sequence Stratigraphy, Facies Analysis and Reservoir Characterization of the Bakken Formation, Viewfield Pool, Southeast Saskatchewan

Abstract

The Viewfield Pool in SE Saskatchewan is the largest Bakken pool on the Canadian side of the Williston Basin, covering approximately 850 sections (square miles). The study area encompasses an area from TWP5 to 14, R3–13W2. The late Devonian early Mississippian Bakken Formation consists of three members in this area, including the productive middle member, which is dominated by mixed siliciclastic and dolomitic silt to very fine grained sandstone which occur between the upper and lower organic rich shale members. The shale members are thermally immature indicating the resource within the Viewfield Pool has migrated from deeper parts of the Williston Basin to the south. Despite a relatively simple well log signature, the depositional history is quite complex, resulting in a great degree of reservoir heterogeneity within the Middle Bakken Member. Detailed core analysis reveals nine lithofacies present in the Viewfield Pool area. These facies are grouped into four distinct facies associations that can be recognized on petrophysical logs and correlated across the study area. A high resolution sequence stratigraphic framework was established and four systems tracts are clearly identified. The lateral distribution of these systems tracts and associated facies, along with abundant production data suggest a simple stratigraphic pinch out of the high stand systems tract to be responsible for trapping oil in this pool, solidifying interpretations from previous regional studies. Furthermore, a detailed geochemical study using an Olympus X-5000 portable X-Ray Florescence (XRF) instrument was conducted on over 1800 samples from 30 cores within the Viewfield area. XRF analysis demonstrates the facies associations are geochemically and therefore mineralogically distinct. In particular, silica (Si), calcium (Ca), potassium (K), aluminium (Al), iron (Fe), zirconium (Zr), and rubidium (Rb) exhibit distinct clusters of data on bivariate plots that differentiate facies associations and even individual facies, thus further supporting the stratigraphic model. A cross plot of calcium content (normalized to silica) and porosity demonstrates a very strong inverse correlation, likely related to the varying degrees of carbonate cementation observed within the reservoir.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015