--> The Implications of Tectonic Events and Overpressure Linkage for Productive Potential of Lower Silurian and Upper Ordovician Black Shale

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The Implications of Tectonic Events and Overpressure Linkage for Productive Potential of Lower Silurian and Upper Ordovician Black Shale

Abstract

The Longmaxi-Wufeng Shale, Lower Silurian and Upper Ordovician black shale that covers a broad area of the Sichuan Basin/Yangtze Platform region is unique with very high thermal maturity and tectonically complex active setting. The Sichuan Basin with comparatively favorable Lower Paleozoic shale geology is multi-tectonic events stacked basin located in the northwest of Yangze Platform, through passive margin Sinian (Precambrian) into foreland basin from Mesozoic to Cenozoic. In this paper, we discuss the impact of the long-term and the short term cycles variations in the distribution and quality of organic matter rich shale reservoirs through a completed sequential analysis. At the same time, the Central Uplift zone provides an interesting case in which the system evolved from overpressure to normal pressure due to the effects of uplift and erosion to well understand the heterogeneousness in these geologically complex reservoirs. Abnormally large fluid pressure, which is of critical consideration in screening prospective targets, has been encountered from widely separated localities with high production rates drilled in the Eastern and Southern Sichuan Basin. However, the mechanisms responsible for over-pressuring have not been conducted and there are even many obstacles and uncertainties to identify productive potential of the shale plays under considerably structural complexity during the process of transforming historical regional extension into present-day active compression. The studies of some bedding-parallel and perpendicular veins taken from over-mature marine shale zones are integrated with burial and thermal history, as an indicator of evolution processes to provide information on the generation and evolution of overpressures in lower Paleozoic shale gas formation of the Sichuan Basin. Further consideration of tectonic compression in different geologic setting is taken in our study to shed light on the dynamic processes involved in the preservation potential of subsurface high fluid overpressures. Evidences suggest that considerable structural complexity is not always negative for the Lower Paleozoic shale in Southern China. Process-based analysis for multivariate is one of ways to improve understanding specific shale reservoirs and production potential. There are many significant benefits to the large scale resource discovery, fracturing, and production challenges in Yangtze region.