Seismic Models of 15 Stratigraphically Controlled Oil and Gas Fields Containing Sandstone Reservoirs in Rocky Mountain Basins: ABSTRACT

Abstract

Two-dimensional, normal-incidence, ray-theory seismic models were generated for 15 stratigraphic traps which have accumulated oil and gas in the Rocky Mountain province. The investigation is a feasibility study to determine the seismic character of moderate-sized (6-30 m thick), lenticular sandstone reservoirs in Rocky Mountain basins. The models are noise free and do not include all the complexities of the seismic phenomenon, but they do provide a reasonable indication of the anomaly to be expected for a specific problem and the quality of seismic data required to solve it. The fields chosen for the model studies represent different kinds of stratigraphic traps, and the reservoirs range in age from Late Pennsylvanian to Late Cretaceous. The fields include nine from the P wder River basin, three from the Denver basin, two from the Green River basin, and one from the San Juan basin. Each seismic model was constructed from a detailed geologic cross section and typically consists of 30 layers and several hundred velocity and density values. Effects of inelastic attenuation, interbed multiples and diffractions, are not incorporated in these seismic models. Hydrocarbon effects should be partly represented through the response of acoustic and density logs from which the models were derived. Final synthetic seismic sections are displayed with symmetrical Ricker wavelets at three different frequencies. Many of the 15 fields investigated appear to be detectable on conventional seismic sections, although several of the anomalies are very subtle. The seismic expression of the objectives modeled are manifested by amplitude changes due to acoustic contrasts at stratigraphic boundaries, or to constructive interference of waveforms. End_of_Article - Last_Page 778------------