Ernest C. Hauser, Ph.D. (Committee Chair); Paul McColgan, Ph.D. (Committee Co-Chair); Doyle R. Watts , Ph.D. (Committee Member)
Master of Science (MS)
Amplitude anomalies in pre-stack seismic data have widely been used in the oil and gas industry as a risk analysis tool when exploring for hydrocarbons. AVO analysis is most often applied to poorly consolidated Tertiary rocks due to the compressibility of these strata when natural gas and porosity are present. In contrast, well-lithified carbonate rocks are less prone to producing a pre-stack amplitude response due to the rigidity of their frame. Pre-stack seismic data of a 2-D seismic profile were conditioned and interpreted to identify amplitude variation with offset (AVO) attributes corresponding to the presence of hydrocarbons within the North Vernon Limestone (NVL) interval in the Illinois Basin. The seismic data were acquired over the Glen Ayr oil field in Vigo County, Indiana, and in the Old Hill oil field in Clay County, Indiana prior to wells being drilled. Production in both fields is from porous dolomites draped by tight limestone or dolomites over a Silurian reef complex We show that with appropriate pre-stack data conditioning subtle AVO responses in Illinois Basin carbonates may indicate the presence of hydrocarbons. Seismic line CM-46-12 (Clay) and CM-27-14 (Vigo) were both analyzed using AVO attributes to identify anomalous zones that may relate to the presence of hydrocarbons. Seismic Line CM-27-14 was further interpreted using pre-stack inversion to provide additional information pertaining to the reservoir rock properties. The results on both seismic lines show strong, negative AVO gradients along the NVL interval, whereas nonproductive intervals exhibit either positive or no amplitude gradient. Pre-stack inversion of lime CM-27-14 shows high impedance zones which are consistent with the presence of tight dolomite atop the reef structure. Low-impedance, low VP/VS ratio zones correlate to the hydrocarbon bearing porosity zones of the NVL interval.
Department or Program
Department of Earth and Environmental Sciences
Year Degree Awarded
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