Abstract

The objective of this case study is to predict whether 5 years of water-flood production from a thinly layered Gulf of Mexico reservoir will change its seismic amplitude-variation-with-offset (AVO) response in a detectable manner. Density and velocity profiles were computed from in situ wireline logs for 100% oil, gas, and brine saturations and for a 5-year prediction that was based on a fluid-flow and production simulation. Analytical AVO curves for simple half-space models did not match AVO curves extracted from synthetic seismograms computed with a full-waveform layer-stack algorithm. Several different amplitude corrections were tried to reduce the AVO curves from the synthetic data to the analytical ones, but, ultimately, none was deemed satisfactory. Instead, AVO change attributes based on relative changes, polarity changes, or ratios were used. Attributes based on the change of AVO gradient were perceived to be most diagnostic of the water flood, but they were also overly sensitive to interference noise and amplitude correction errors. For field data from the study area, a large decrease in intercept magnitude may be the best indicator of the waterfront.

You do not currently have access to this article.