An amplitude versus offset (AVO) study was undertaken for Lines ECL-1 and -2 and Well A of the United Kingdom North Sea to determine if variations in fluid saturation can be detected in Eocene sand mounds. These features are a major play in this area. The Eocene sands contain gas and oil in Well A. Elastic modeling using the well data was done to match the seismic common midpoint (CMP) gather. Target zone fluid saturations in the model were then altered to investigate changes in AVO and stacked trace response. The model and field data were processed using the same processing steps and parameters. Seismic offset dependent amplitude stack (SODAS), a color display system, was used to display the AVO results for the field and model data. It was found that gas, oil, and water sands could be distinguished from each other, though full and partial gas saturation were indistinguishable. Clay content, porosity, and multiple reflections also had important effects on the AVO response. On the basis of the hydrocarbon indicators that were investigated we then interpreted the hydrocarbon limits on Line ECL-1 with well control and evaluated Line ECL-2, which has an undrilled prospect. From our analysis, we concluded that waterbearing sands were most likely present in the prospect area on Line ECL-2, though the data is rather inconclusive.
Effects of non-uniform fluid saturation distribution on pressure transient analysis