A Case History of Geoseismic Modeling of Basal Morrow–Springer Sandstones, Watonga-Chickasha Trend: Geary, Oklahoma—T13N, R10W1
William A. Clement, 1977. "A Case History of Geoseismic Modeling of Basal Morrow–Springer Sandstones, Watonga-Chickasha Trend: Geary, Oklahoma—T13N, R10W", Seismic Stratigraphy — Applications to Hydrocarbon Exploration, Charles E. Payton
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The project area is along the northeastern flank of the Anadarko basin, near Geary, Oklahoma. In the area, basal Pennsylvanian Morrow–Springer sandstones subcrop beneath the pre-Atokan, Wichitan unconformity and form the prolific gas condensate-producing Watonga-Chickasha trend.
Productive Morrow–Springer distributary channel sandstones form discontinuous lenticular reservoirs. Dense well control is normally required to map sandstone geometry and distribution. Integration of high resolution seismic data, with the application of geoseismic modeling techniques which use geologically derived input parameters, can better delineate the shape and extent of these reservoirs between points of well control. Vibroseis®seismic data, filtered conventional dynamite data, synthetic seismograms from sonic logs, one-dimensional geoseismic models, and geologic/ lithologic data from well cuttings, cores, and logs, can be used to construct meaningful sandstone distribution maps. Geoseismic models constructed by use of a remote computer terminal demonstrate that high resolution 12 to 67-Hz seismic data can distinguish sandstones to a minimum thickness of 20 ft (6 m) when Stratigraphic conditions are such that high interval velocity (15,000 to 15,500 ft/sec or 4,572 to 4,724 m/sec) sandstones are encased in lower interval velocity (10,000 to 11,500 ft/sec or 3,048 to 3,505 m/ sec) shales. Reflection coefficients between sandstones and shales range from 0.1 to 0.3. Results of the modeling indicate that sandstones exceeding 20 ft (6 m) in thickness are arranged in a NW-SE trend, approximately 2,500 ft (762 m) wide, across the project area in T13N, R10W.
Subsequent development drilling has yielded both positive and negative results. Two wells encountered the predicted basal sandstone; one well encountered thin interbedded tight sandstones and shales. Lateral facies change from thick porous sandstone to interbedded high interval velocity facies (17,000 ± ft/sec or 5,182 ± m/sec); tight, highly indurated sandstones and shales can produce similar seismic signatures. Modeling of high resolution seismic data can accurately predict the presence of high velocity zones within the basal Morrow–Springer section, but further criteria must be applied to distinguish productive sandstones from thin, high-velocity sandstones interbedded with shales.
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Papers from a research symposium at the 1975 American Association of Petroleum Geologists and supplemented by later reports became “Seismic Stratigraphy Applications to Hydrocarbon Exploration”, one of AAPG’s best-selling book publications. Dramatic improvements in seismic imaging were demonstrated, a result of developments in seismic data quality and the processing capability of electronic technology. Twenty-eight articles are grouped into three sections. The first describes principles that both permit and also limit interpretations. The second section presents sixteen articles that describe the qualitative approach to stratigraphic interpretations of reflection records, and the final section presents techniques and examples of modeling. Of particular interest are a series of eleven papers in the second section under the subject heading of “Seismic stratigraphy and global changes of sea level”. Prepared by P. R. Vail, R. M. Mitchum and others from Exxon, they describe the regional unconformities and stratigraphic changes resulting from sea level fluctuations, and the manner in which these changes can be interpreted from seismic surveys. For many individuals within the oil industry who purchased this book, it was their first introduction to the modern concept of sequence stratigraphy that would have a major impact on the methodology of petroleum exploration.