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During this last quarter of the "Seismic Evaluation of Hydrocarbon Saturation in DeepWater Reservoirs" project (Grant/Cooperative Agreement DE-FC26-02NT15342), we have moved forward on several fronts, including data acquisition as well as analysis and application.During this quarter we have:Completed our site selection (finally). Measured fluid effects in Troika deep water sand sample -Applied the result to Ursa 'fizz gas' zone -Compared thin layer property averaging on AVO response -Developed target oriented NMO stretch correction -Examined thin bed effects on A-B crossplotsBegun incorporating outcrop descriptive models in seismic forward models Several factors can contribute to limit our ability to extract accurate hydrocarbon saturations in deep water environments. Rock and fluid properties are one factor, since, for example, hydrocarbon properties will be considerably different with great depths (high pressure) when compared to shallow properties. Significant over pressure, on the other hand will make the rocks behave as if they were shallower. In addition to the physical properties, the scale and tuning will alter our hydrocarbon indicators. Reservoirs composed of thin bed effects will broaden the reflection amplitude distribution with incident angle. Normal move out (NMO) stretch corrections based on frequency shifts can be applied to offset this effect. Tuning will also disturb the location of extracted amplitudes on AVO intercept and gradient (A-B) plots. Many deep water reservoirs fall this tuning thickness range. Our goal for the remaining project period is to systematically combine and document these various effects for use in deep water exploration.Agreement DE-FC26-02NT15342, Seismic Evaluation of Hydrocarbon Saturation, 3

Abstract:The "Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs" (Grant/Cooperative Agreement DE-FC26-02NT15342) began September 1, 2002. During this second quarter:-A Direct Hydrocarbon Indicator (DHI) symposium was held at UH -Current DHI methods were presented and forecasts made on future techniques.-Dr. Han moved his laboratory from HARC to the University of Houston.-Subcontracts were re-initiated with UH and TAMU.-Theoretical and numerical modeling work began at TAMU -Geophysical Development Corp. agreed to provide petrophysical data.-Negotiations were begun with Veritas GDC to obtain limited seismic data.-Software licensing and training schedules were arranged with Paradigm.-Data selection and acquisition continues.The broad industry symposium on Direct Hydrocarbon Indicators was held at the University of Houston as part of this project. This meeting was well attended and well received. A large amount of information was presented, not only on application of the current state of the art, but also on expected future trends.Although acquisition of appropriate seismic data was expected to be a significant problem, progress has been made. A 3-D seismic data set from the shelf has been installed at Texas A&M University and analysis begun. Veritas GDC has expressed a willingness to provide data in the deep Gulf of Mexico. Data may also be available from TGS.Agreement DE-FC26-02NT15342, Seismic Evaluation of Hydrocarbon Saturation 4Contents:

Invasion of drilling or completion fluids from the borehole into the surrounding formation can alter seismic impedances significantly. Filtrates will behave differently to pressure. temperature, and gas content. Oil based filtrates can absorb substantial gas. Both sonic and density logs are modified and corrections can be significant for seismic-log ties.

Recovery processes are complex and usually oversimplified in geophysics. Time lapse seismic monitoring of these different processes will often be complicated and lead to conflicting interpretations. Pressure, temperature, or density changes can out weigh effects due to fluid replacement. Small concentrations of free gas can appear even during liquid or supercritical injection and will lower velocities unexpectedly. Fluid compositional and phase analysis can help predict the seismic response.