A critical mini-review of key issues on sweet spot identification for shale gas reservoirs

The successful commercial development of high-quality middle-shallow and middle-deep shale gas in the Sichuan Basin marks a significant achievement. With the escalating energy demand, attention has shifted toward exploring and exploiting deep-buried, low-quality middle-shallow, and middle-deep shale gas reservoirs in China. This shift necessitates advancements in geological evaluation and engineering design. Here, the key issues related to sweet spot identification in shale gas reservoirs are introduced, and three correlated parameters (gas-in-place, microstructure, and permeability) are concisely overviewed. Numerous efforts and advances have been dedicated to characterizing these parameters in recent years, attempting to reveal the underlying mechanisms and identify the appropriate evaluation methods. However, challenges persist, and potential improvement opportunities are outlined here to provide insights for researchers.