Correlation between rock properties and spatial variations in seismic attributes for unconventional gas shales—A case study on the Haynesville Shale

Abstract

Spatial variations in seismic attributes, such as P-wave amplitude and inverted P-impedance, are correlated with the rock properties that are important for the exploration and production of unconventional gas shales. It is important to know which rock properties or combination of properties cause the spatial variations. In this study, we have estimated three important rock properties (porosity, composition and pore shape) at the seismic scale by combining seismic inversion with a rock physics modeling workflow. We found that different P-impedances correspond to different distributions of porosity, composition and pore shape. Thus, the spatial variations in seismic attributes depend on all these rock properties. In general, large porosity, softer composition, and small pore aspect ratios correspond to lower P-impedance. However, lower P-impedance does not necessarily always correspond to large porosity, softer composition and small pore aspect ratio because these rock properties jointly affect the seismic attributes. One or two of them possibly dominate the effect on P-impedance. Therefore, these rock properties need to be investigated simultaneously. Continuous distributions of porosity, composition and pore aspect ratio will be estimated in the 3D seismic block by the same procedure, and we will be able to understand how the rock properties contribute to the seismic attribute spatial variations in a more comprehensive way, including an assessment of the uncertainty.