Shale gas characterisation for hydrocarbon accumulation and brittleness by integrating a rock-physics-based framework with effective reservoir parameters

Abstract

Efficient exploration and development of shale gas require the identification of reservoirs with abundant hydrocarbon accumulation and high brittleness. However, realistic descriptions and seismic visibility of these reservoir properties have not been thoroughly investigated due to the complex elastic responses of organic shale. This study develops a new rock-physics-based framework incorporated with proposed effective reservoir parameters to evaluate hydrocarbon accumulation and brittleness in shale gas reservoirs. The developed rock physics model quantitatively relates the elastic characteristics of organic shale to the controlling factors of gas enrichment and brittleness that are realistically represented by the proposed effective reservoir parameters. Moreover, the rock physics template (RPT) computed using the proposed model represents a powerful tool to reveal implicit correlations between the effective reservoir parameters and elastic attributes in organic shale. In a real data application related to the Longmaxi shale gas reservoir in the Sichuan Basin, the constructed RPT provides reliable estimates of effective reservoir parameters using seismic-inverted elastic attributes, with the results being validated by logging data from gas-producing wells. Furthermore, reservoir classification based on the RPT and effective reservoir parameters offers a practical way to identify geological and engineering sweet spots, yielding valuable insights into reservoir qualities associated with gas enrichment and brittleness for locating promising shale gas areas. The predicted results indicate that high-quality shale gas reservoirs exhibit a structure-related distribution with potential geological significance.