Synthetic Seismograms Related to Detailed Geology in the Celtic Field, Saskatchewan
Lomas, Margaret Kathleen
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In the L10ydminster area of Saskatchewan, heavy oil commonly occurs in thin, less than five-metre thick, vertically-stacked lenses within the sand beds of the Lower Cretaceous Mannville Group. Seismic mapping of the Mannville section has proved difficult due to the thinness of the beds, the lateral variation of these beds, and the lack of acoustic markers. The comparison of synthetic seismograms to detailed stratigraphic and core-analysis data allowed the interpretation of subtle seismic responses on these computer-simulated seismograms. Synthetic seismograms, which included the effects of absorption and dispersion, were constructed for seven closely-spaced wells located in and near an enhanced-recovery pilot-project in the Celtic field. Input parameters of an impulse source buried at 29.9 m and a Q curve derived from published Q-values provided the best synthetic-seismic response to the zones of economic importance located within the Mannville Group. In the Celtic field, the seismic-reflection method could be used for heavy-oil exploration or development if sufficient frequency-content in the 60 to 115 hz range is returned from the Mannville section. However, the dominant frequency imposed by the natural filtering of the earth is only 39 hz in all but one of the wells studied. Data acquisition and processing techniques must, therefore, be chosen to accentuate the 60 to 115 hz range.