There has been a lot of research on the shale gas geological conditions in Hunan Province in recent years, but there has been little research and estimation on the tectonic conditions of shale gas preservation, which affects scientific deployment of regional shale gas exploration. The authors carried out 1∶50 000 shale gas geological survey on the Shuiling-Damiaokou area, northwest periphery of Yongzhou depression, central-southern Hunan, studied the structure characteristics and tectonic evolution, and then probed into the tectonic conditions of shale gas preservation. In the survey area, there occur strong deformations including NNW- to SN-trending folds mainly and EW-trending folds secondly in Upper Paleozoic, NNE-trending and NE-trending kink structures in Lower Paleozoic, NNW- to SN-trending, NE-trending and NW-trending faults（mainly thrust and normal faults with minor strike-slip faults）cutting Lower and Upper Paleozoic, violent NNW-trending slaty cleavages in Lower Paleozoic, SN-trending and NNE-trending fracture cleavages in Devonian Tiaomajian Formation. Combined with regional tectonic settings, 8 deformation events related with above deformations have been determined primarily since Early Paleozoic. In the deformation events, the compressive events such as Caledonian Movement, Indosinian Movement and Early Yanshanian Movement, and Cretaceous regional extensional event were most important. The black shale of Ordovician Yanxi Formation and bottom Tianmashan Formation is shale gas target layer of the survey area. Canister desorption experiments with the samples collected from drill core indicated that the gas-bearing property of the target layer is very poor. Several tectonic movements caused rising and denudation of the survey area, which made shale gas escape and made the target layer preserved locally only. Complicated structure styles formed by several tectonic movements make it be difficult to ascertain the expanding characteristics of the garget layer under Upper Paleozoic. Caledonian Movement and Indosinian Movement caused granitic magmatism and respondent high geothermal field, which improved thermal evolution stages of organic matter considerably, and made shale gas preservation to be difficult. The unfavourable tectonic conditions of shale gas preservation in survery area is introduced in Yongzhou depression and its adjacent areas, therefore shale gas potentialities in the areas are very limited. This paper is of great importance to the study and objective knowledge of regional shale gas reservoir and to shale gas prospecting arrangement.
Bai Daoyuan Xiong Xiong Jiang Wen. Geological structure characteristics of Damiaokou area in central-southern Hunan andtheir significance to regional shale gas preservation conditions[J]. Chinese Journal of Geology, 2018, 53(2): 510-530.