Structural evolution and characterization of organic-rich shale from macroscopic to microscopic resolution: The significance of tectonic activity

Abstract

Shale gas exploration and development have taken significant strides in the relatively straightforward intra-basin stability zone and intra-basin weak deformation zone of marine shale in the Sichuan Basin, South China. In addition, the extra-basin strong tectonic modification zones have been actively explored. However, the results have been limited, which reveals the complexity of shale gas formation and preservation conditions in the context of multi-scale geological processes. These tectonic geological conditions have a significant impact on the shale gas content, while it has been difficult to figure out how tectonic deformation modifies reservoir structure and what specific mechanism causes shale gas content anomalies. Based on subjecting geologic samples to combined hightemperature and high-pressure experiments, this study summarizes the tectonic constraint mechanism of shale petrophysical structure evolution and its impact on shale gas storage, reveals the intrinsic connection and mechanism of shale pore-fracture and organic matter, inorganic mineral particle structure evolution and tectonic stress, and identifies the remodeling mechanism of the shale reservoir physical property change. The findings contribute to the theory of shale deformation and gas accumulation, as well as offer a scientific foundation for the exploration of marine shale gas in the complex tectonic zones outside the Sichuan Basin.

Hydrocarbon fluid evolution and accumulation process in ultradeep reservoirs of the northern Fuman Oilfield, Tarim Basin

“…At this time, the source rock of the Yuertusi Formation reached the hydrocarbon generation stage and began to release hydrocarbons (Cai et al, 2016;He et al, 2020;He et al, 2022a;He et al, 2022b); liquid hydrocarbons migrated upward to the Middle and Lower Ordovician strata along the vertical fracture, and a large amount of low-maturity crude oil was charged into the reservoir to form an oil reservoir. In the early Hercynian period, some tectonic uplift activities and the reactivation of strike-slip faults with a northwest strike led to the formation of new fractures and caverns, and the calcite filled with fractures and caverns broke under the action of tectonic activity (Zhu H. et al, 2021;Gao et al, 2023). At the end of the Devonian, tectonic uplift basically ended, and the source rocks of the Yuertusi Formation as a whole reached the stage of high-maturity hydrocarbon generation.…”

Depositional Model and Controlling Factors of High-Quality Shales of the Wufeng and Longmaxi Formations in Western Chongqing, Sichuan Basin, China

“…Deep-buried shale in the Sichuan Basin, over 4500 m beneath the surface, is the future target in which over 60% of shale gas is trapped. , However, it is a great challenge to explore the deeply buried shale, due to the created complex distribution of geostresses in deep-buried depth and the uncertain distributions of high-quality shales in different tectonic zones, the latter of which are the key to exploration of deep shale gas. To address this issue, previous researchers have conducted numerous studies and the development of high-quality shales has been attributed to several factors such as redox conditions, marine primary productivity, terrestrial clastic input, tectonic evolution, and sea level fluctuations; these factors complicate the prediction of high-quality shales of the Longmaxi Formation (Yan et al) and control the transformation of redox conditions (Dong et al; Lu et al). , At the microscale, size and morphology of micropores have a significant effect on the gas state and content of trapped gas within shale reservoirs (Gao et al), and the structure of micropores in different lithofacies displays distinct gas storage capacity of organic matter (Lin et al) .…”

Production characteristics and influencing factors of coalbed methane wells: a case study of the high-ranking coal seam in the southeastern Qinshui Basin, China

“…CBM, characterized by its non-toxic combustion, absence of particulate matter emissions, and lower carbon dioxide release compared to coal, oil, or wood, is acknowledged as a clean fuel (Chen et al, 2017;Peng et al, 2017;Kong et al, 2022;Ni et al, 2023). Over the past 2 decades, CBM has emerged as a significant energy resource and is anticipated to play a pivotal role in meeting future global energy demands (Moore, 2012;Lou et al, 2013;Fu et al, 2017;Gao et al, 2023a;Ifrene et al, 2023;Wang et al, 2024a). China, as the current global leader in coal consumption and production, can benefit from the development of CBM resources.…”