Seismic Models of Fifteen Stratigraphically Controlled Oil and Gas Fields with Sandstone Reservoirs, Rocky Mountain Basins: ABSTRACT

Abstract

Two-dimensional seismic models, derived from both normal-incidence ray-theory and wave-theory solutions, were generated for 15 stratigraphically trapped oil and gas accumulations in the Rocky Mountain province. The investigation is a feasibility study to determine the seismic character of moderate-sized (6 to 30 m thick), lenticular sandstone reservoirs in Rocky Mountains basins. The models are noise free and do not include all the complexities of the seismic phenomena, 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 four major classes of stratigraphic traps and the reservoirs range in age from Late Pennsylvanian to Late retaceous. The fields include Bell Creek, Dillinger Ranch, Pine Lodge, Raven Creek, Red Bird, Rozet, South Glenrock, Well Draw, and West Salt Creek from the Powder River basin; Adena, Holster-Third Creek, and Peoria from the Denver basin; Desert Springs and Patrick Draw from the greater Green River basin; and Horseshoe Canyon 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. No estimates of the effects of inelastic attenuation, interbed multiples, or hydrocarbon saturation are included; however, the latter parameter should be partly accounted for in the acoustic and density-log values. Final synthetic seismic sections are displayed with 80-, 60-, and 40-Hz symmetrical Ricker wavelets. Our study indicates that the trap-reservoir interface of all 15 examples may be detected using the 40-Hz Ricker wavelet and thus would have a reasonable chance of being recognized on a conventional seismic section. Several of the documented anomalies are very subtle. The seismic anomalies are generally manifested as amplitude increases owing to either marked acoustic contrasts at the boundaries of a stratigraphic unit or to the constructive interference of waveforms interacting with numerous stratigraphic horizons (i.e., tuning). End_of_Article - Last_Page 840------------