重庆及其周缘地区下古生界页岩气资源勘探潜力

四川盆地经历了从震旦纪到中三叠世的克拉通和晚三叠世到新生代的前陆盆地2个构造演化过程，在克拉通盆地演化阶段主要发育一套巨厚的海相沉积。晚震旦世和中奥陶世开始的2次大规模海侵作用，在深水环境中沉积了下寒武统筇竹寺组、上奥陶统五峰组-下志留统龙马溪组2套黑色页岩。由于该盆地演化过程中复杂的构造变动，重庆及其周缘地区的区域构造主要以高幅抬升及强烈挤压为特点，下古生界埋藏浅、变形严重、破坏强烈，现今构造形态表现为高陡状褶皱，形成了与美国东部典型页岩气盆地相似的构造演化特点和地质条件。研究表明，该区具有页岩气富集的有利地质条件，是页岩气勘探研究值得关注的重要领域。采用体积法对该区下寒武统筇竹寺组、上奥陶统五峰组-下志留统龙马溪组页岩气资源量做了初步估算。结果表明：重庆及其周缘地区筇竹寺组页岩气资源量约为7.5×10₁₂ m₃，五峰组-龙马溪组页岩气资源量约为11.5×10₁₂ m₃，显示出该区巨大的页岩气资源勘探潜力。

Potentials of the Lower Palaeozoic shale gas resources in Chongqing and its adjacent areas

Tectonic evolution of the Sichuan Basin can be divided into two stages: a stage of a cratonic basin from the Sinian to the Middle Triassic and a stage of a foreland basin stage from the Late Triassic to the Neogene. In the former stage, very thick marine deposits were accumulated. Two large-scale transgression events occurred in the Late Sinian and the Middle Ordovician, during which two sets of dark shale, one of which is the Lower Cambrian Qiongzhusi Formation and the other one is from the Upper Ordovician Wufeng Formation to the Lower Silurian Longmaxi Formation, were deposited respectively. As the tectonic events are complex in the process of basin evolution, the tectonic actions in Chongqing and its adjacent areas are characterized by high uplifting and strong compression. The Lower Paleozoic is shallow in burial depth, serious in deformation and strong in destruction. The present structure is presented by steep fold. The characteristics of tectonic evolution and geologic conditions in the study area are similar to those in the typical shale gas basins of the eastern U.S.A. The study area has the favorable conditions for shale gas accumulation, thus is an important frontier for shale gas exploration. Preliminary estimation with the volumetric method shows that the shale gas volume in the Qiongzhusi Formation is 7.5 tcm and that in the Wufeng-Longmaxi Formations is 11.5 tcm, which significantly shows a great potential for shale gas exploration in Chongqing and its adjacent areas.