ABSTRACT

Diagenesis, porosity, and bitumen saturation of the Grosmont Formation, as well as the underlying and overlying strata (where cored), have been studied in the area between ranges 16 W4 to 25 W4 and townships 80 to 95. Porosity of some facies has been significantly enhanced through diagenesis. Most bitumen is concentrated in secondary pores, in fractures, and in karst fillings.

Our data suggest that the best porosity-permeability relationship is displayed by the Upper Grosmont 2. In the other three Grosmont units, individual permeability values correspond to larger ranges in porosity, probably caused by the presence of various porosity types. Plots of the porosity-permeability data suggests that each Grosmont unit is dominated by a different type of porosity or combination of porosity types. Hg-capillary pressure measurements indicate that the dolomite samples can be classified into at least four petrophysical rock types defined by different pore throat properties. These types may be redefined, and more types may be discovered, as more samples are analyzed. The four preliminary petrophysical rock types are related to porosity types, crystal size and fabric, and mineralogy (calcite or dolomite).

In general our study indicates that the Grosmont dolomites can be subdivided into several diagenetic and petrophysical types and that the two groups do not necessarily coincide. Ongoing studies will reveal whether these relationships can be used for prediction of reservoir characteristics.

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