Obtaining permeability from seismic data - A new breakthrough in carbonate reservoir modelling
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abstract
Shell's Carbonate Team has been developing a method in which post-stack seismic can be used to estimate average interval matrix permeability in carbonates. The foundation of the technique is a new model, which describes quantitative relationships between sonic velocity, porosity and permeability. This model relates a pore shape factor from the poro-elasticity theory with permeability from lab measurements. This pore shape factor describes the 3D pore structure and can be extracted from inverted post-stack seismic data. Additionally, this factor relates to pore connectivity and, therefore, to permeability. After the concept was tested and successfully proven on plug scale, the first implementation focused on a large carbonate field in the Middle East. This accumulation had all the ingredients to perform a full field test of the concept - good thickness for multiple seismic reflections, matrix-dominated permeability, single mineralogy (calcite), superb seismic data and enough wells with good compressional and shear sonic logs. Introducing pore structures in the characterisation of carbonate reservoirs from acoustic data helps resolve the ambiguity in porosity/permeability prediction. In the test case, we have demonstrated that: 1) the new rock property prediction is much more accurate than properties predicted by commercial inversion packages, 2) pore structure can be extracted from 3-D post-stack seismic, 3) a permeability indicator can be estimated from inverted seismic and 4) a permeability indicator volume proved to produce a superior history match against a permeability model constructed from extensive well data.
