Geological and computer traps in petroleum exploration

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Department of Geological and Mining Engineering and Sciences


Structure contour maps on top of the Viola Limestone in the southern portion of the Forest City Basin were computer contoured for 5-year intervals from 1950 to 1985 using raw data and first-through sixth-degree trend surfaces and residuals. The trend surfaces show maximum improvement in correlation coefficient and sum of squares in 1960. A shift in the position of positive residuals from west to east was located in going from low to higher ordered surfaces. Production was concentrated in the + 60 to + 79-ft residual contour interval. Prediction of residual value is poor for most contour intervals but, for the time interval 1980-1985, is about 75% accurate. Errors are within one contour interval. Combining probabilities gives +60 to +79-ft as the best interval to drill at present. A prediction of remaining producing or show in the area was arrived at by calculating the frequency distribution of all holes drilled and of dry holes drilled for 50-ft contour intervals using Johnson distributions. The result suggests a number of shows and producers yet to be located, particularly in the subsea elevations below - 1800-ft and above - 1500-ft. Potential is best, of course, where these raw data subsea elevations coincide with a positive residual from the third-degree surface of + 60-+ 79-ft.

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Computers and Geosciences