Abstract:
Southern Sichuan Province has widely developed karsts and densely distributed coal mine goafs, which cannot be accurately detected and identified using a single existent exploration method. Consequently, large-scale and industrial drilling for shale gas is prone to induce failures and complex events. In light of the complex topographic and geological conditions in southern Sichuan, this study conducted tests and comparative analysis using multiple engineering geophysical exploration methods including electrical resistivity imaging, shallow seismic method, transient electromagnetic method, audio-magnetotelluric method, and microtremor survey method. As a result, an integrated engineering geophysical exploration technology for shale gas well platforms in southern Sichuan was formed and applied to the construction of shale gas well platforms. As indicated by drilling results, the integrated technology can effectively identify unfavorable geological bodies (e.g., shallow karsts, coal mine goafs, and overburdens) at a depth of less than 1000 m and provide technical support for siting shale gas well platforms, optimizing casing programs, predicting drilling risks, shortening drilling cycles, and protecting ecological environment, with remarkable economic, social, and ecological benefits having been achieved. Moreover, this integrated technology provides a technical guarantee for the construction of both the Changning-Weiyuan national shale gas demonstration zone and the southern Sichuan shale gas exploration and development pilot zone and accelerates the shale gas development in southern Sichuan.