A rapid approach to evaluating ground surface conditions for shale gas extraction in mountainous areas

Ground surface conditions, regarding the engineering, eco-environmental, and economic constraints, are crucial for shale gas extraction in the mountainous areas. A novel approach has thus been proposed to perform a rapid and integrated evaluation of ground surface conditions on a regional scale. The southeastern margin of the Sichuan Basin, China's primary shale gas exploitation target, serves as an example to demonstrate the execution of this approach. Critical metrics for ground surface condition evaluation, including geomorphology, land utilization, water supply, and transportation conditions, were obtained from published GIS and remote sensing data. Different ratings were assigned to facilitate a quantitative evaluation of the metrics, and the composite index was calculated based on the ratings. The study area was first filtered using a composite index threshold determined from the calculated values at the existing well sites. The contiguous regions with the sufficient dimensions within the screened area were further selected as the final potential targets. The overall assessment recommended that only 10.99%, 7.61%, and 4.86% of the study area be deemed marginally, moderately, and highly suitable for potential shale gas extraction sites, respectively. These results suggest that this approach can enable efficient and accurate ground surface condition evaluations beyond the actual field surveys, while excluding the most unsuitable areas for further shale gas extraction site selection.