Browsing by Author "Cann, Blair Charles"

Now showing 1 - 1 of 1
  • Thumbnail Image
    ItemOpen Access
    Lithofacies Determination in the Willesden Green and South Pembina Duvernay Formation: Creation, Characterization, and Correlation
    (2018-12-14) Cann, Blair Charles; Lines, Laurence R.; Meyer, Rudi; Clarkson, Christopher R.
    This study proposes a set of lithofacies in the Southern West Shale Basin of the Duvernay Formation that characterize variation at core and thin section scales, correlate with conventional well logs and can be further related to geochemical data, elastic properties, elastic property-based brittleness indices, mineralogical brittleness indices, and basic source rock data. A sedimentological assessment of seven wells was performed and the resultant data used to define the proposed lithofacies. The lithofacies relate to natural lithological subdivisions seen in the core. Colour was successfully utilized as one of the primary lithofacies characteristics and has resulted in a substantial degree of correlatability with conventional well logs and source rock data and a more moderate degree of correlatability with elastic properties and geochemical data. It is proposed that these lithofacies display a predictable and logical progression of environmental change within the Duvernay Formation that can be related to cyclical deposition and sequences in a restricted basin with a stratified water column that is affected by variations in energy, oxygenation, and most probably sea level. The relationship between primary lithofacies and conventional well logs indicates that by utilizing the gamma ray log as the principal lithological indicator, and density porosity, neutron porosity, sonic and PE (photoelectric factor) logs in situations of uncertainty, the lithofacies can be extrapolated using conventional well logs. Based on statistical analysis, 75% of the time Defined gamma ray cut-offs for the most common lithofacies in the Duvernay Formation can predict the lithofacies and the trends in the other logs should be applied in association with gamma ray cut-offs to confirm determined lithofacies and to help determine lithofacies in situations of uncertainty. Source rock data that includes S1 (Amount of free hydrocarbon), S2 (remaining hydrocarbon generating potential) and TOC (total organic carbon) correlate well with the lithofacies and these reservoir characteristics may be extrapolated utilizing the defined primary lithofacies. Geochemical data shows the connectivity of disparate facies as the same component parts are present in all facies while their percentages vary. This encourages an interpretation of connected cyclical deposition driven by sequences. Trends in average values can be related to the primary lithofacies and these primary lithofacies are interpreted to represent the sequence of changing depositional conditions. Even though trends in geochemical data are observed substantial overlap between facies occurs. Geochemical variance within a given facies is attributed to shorter lived fluctuations in depositional conditions. Trends seen in elastic properties are mostly tied to geochemical variations in the matrix that include clay, TOC and micrite; however, recrystallized carbonate appears to have a large influence when present. Quartz and carbonate silts and carbonate fossil fragments appear to have a much more negligible effect on elastic properties. Unexpectedly the combined effect of increased organic matter and clay appears to lower Poisson’s ratio, and this requires further study. Only some brittleness indices display trends related to lithofacies and these can lack in consistency. Different brittleness indices are responding to different properties of the rock, and all could be successful in different situations. These properties primarily appear to include high Young’s modulus, low Poisson’s ratio, high clay fraction, and organic matter percentage. It appears that when choosing brittleness determination methods in this area of the Duvernay Formation, and potentially in other unconventional source rock hydrocarbon plays, careful consideration of the properties of the formation and the type of response desired is required, and perhaps several methods could be applied concurrently. The correlativity of the lithofacies with various data types and their probable relationship with depositional conditions validates the application of them within this area of the Duvernay Formation; and, an application of colour as a primary lithofacies characteristic may be effective when interpreting or correlating other source rock shales deposited in a restricted basin that once probably contained a stratified water column.