During the past four decades, numerous amplitude variation with offset (AVO) attributes has been proposed and implemented to detect seismic expressions associated with hydrocarbon-charged sediments. For the above purpose, the principal AVO attributes, intercept (I) and gradient (G), have been used in a combination to produce another AVO attribute or cross-plotted against each other to detect hydrocarbons. Some of the very common combinations are the product I*G, energy-weighted AVO (En-AVO), fluid factors, and scaled Poisson reflectivity (SPR). The latter attribute is proven sensitive to changes in the Poisson ratio between sediments. Irrespective of sand-shale impedance contrast, the SPR is found always negative for shale over gas-saturated reservoir reflections. On the other hand, gas-saturated sands regardless of their age, depth, and consolidation are commonly characterized by their negative gradient (G) which is also influenced by changes in the Poisson ratio. In order to benefit from the dependence of the two attributes on the Poisson ratio, the product of SPR and G is applied on well and seismic data from North Western Australia to detect hydrocarbon-saturated reservoirs. In addition, a cross-plot of SPR vs gradient is used instead of the commonly used intercept-gradient. The product of SPR and G could help distinguish the gas-saturated reservoirs from their surrounding shale and siltstone. Furthermore, the SPR-G cross-plot shows that hydrocarbon-saturated sandstones can be easily identified in the G-SPR domain. Results from the application of the SPR*G and from the cross-plot are calibrated with well data and found very consistent with information from wells.
- AVO attribute
- Gas-saturated sands
ASJC Scopus subject areas
- Environmental Science(all)
- Earth and Planetary Sciences(all)