Structural deformation characteristics and shale gas preservation conditions in the Zhaotong National Shale Gas Demonstration Area along the southern margin of the Sichuan Basin

Zhao, Xu; Liang, Xing; Lü, Honghua; Zhang, Jiehui; Shu, Honglin; Xu, Yongchang; Wu, Jinyun; Wang, Gaocheng; Lü, Wei; Tang, Xiehua; Shi, Wenrui

doi:10.1016/j.ngib.2019.10.004

Cited by 13 publications

(7 citation statements)

References 5 publications

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“…The tectonic location of the Northeast Yunnan area is at the junction of the Tethys-Himalayan tectonic domain and the coastal Pacific tectonic domain, including first-class tectonic units such as the Sichuan Basin, Kangdian Uplift, and Dianqianbei Depression. , The overall structural traces are dominated by the NE, NW, and near SN directions. The anticline is wide and gentle, and the core is exposed in the Lower Paleozoic Cambrian-Silurian.…”

Section: Geologic Settingmentioning

confidence: 99%

Effect of Faults on Shale Pore Fracture and Shale Gas Preservation: A Case Study of the Wufeng-Longmaxi Formation in the Northeast Yunnan Area

et al. 2022

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The organic-rich shale of the Wufeng-Longmaxi Formation in the Northeast Yunnan area where faults develop has a considerable basis and potential for hydrocarbon generation. A total 16 core samples from well ZD2, which is affected by faults, and well ZY1, which is located in a residual syncline, were collected. The effect of faults on the shale pore fracture and shale gas preservation was investigated primarily through core fracture statistics, field emission scanning electron microscopy, nuclear magnetic resonance (NMR), and triaxial mechanical tests. The results show that high-angle shear and bedding fractures are more developed in well ZD2 than well ZY1, indicating that faulting promotes the development of both bedding and structural fractures. The pore types and morphology of samples affected by faults are significantly different in terms of the compaction of organic matter (OM) pores, reduction of interparticle (interP) pores, increase in dissolution pores and structural microfractures. NMR pore size distributions of the samples primarily show a bimodal distribution, and mesopores (2–50 nm) are the dominate pores. However, faulting can weaken the correlation of pore structure with total organic carbon and minerals content. Comparative studies reveal that the effects of faults on pore structure are manifested as an increase in porosity, a decrease in average pore size, and a leftward shift of the PSD curve. Strongly heterogeneous dissolution substantially increases shale porosity. Tectonic extrusion compacts the OM and interP pores, which reduces the average pore size. The triaxial compressive strength (σTCS) of the samples from well ZY1 is higher than the normal stress on the fault plane. However, considering the correlation between σTCS and mineral content, the Upper Longmaxi Formation has a better fault sealing ability compared to the Wufeng-Lower Longmaxi Formation. Together with the gas-bearing properties of the wells, the Himalayan faults have a good sealing ability in Mugan syncline. Hence, the Himalayan faults with satisfactory sealing can effectively block the escape channels of shale gas along the bedding in a syncline. The wings of gentle syncline covered by overthrusting Himalayan faults are a favorable structural style for shale gas enrichment.

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Section: Geologic Settingmentioning

confidence: 99%

Effect of Faults on Shale Pore Fracture and Shale Gas Preservation: A Case Study of the Wufeng-Longmaxi Formation in the Northeast Yunnan Area

et al. 2022

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“…The influence of structure should be considered in the process of exploration and development. Generally, faults are not conducive to reservoir continuity and preservation conditions, especially normal faults 55 , 56 . The wide and gentle monocline is the best gas enrichment area, and the well-sealed anticline core is also conducive to gas accumulation 57 , 58 .…”

Section: Superimposed Accumulation Mechanism and Model Of Coal-measur...mentioning

confidence: 99%

A model for superimposed coalbed methane, shale gas and tight sandstone reservoirs, Taiyuan Formation, Yushe-Wuxiang Block, eastern Qinshui Basin

Xie

Gan

Chen

et al. 2022

Sci Rep

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Superimposed accumulation mechanism and model of vertical source rock–reservoir system of coal-measure gas is crucial to evaluate the exploration potential, and also the basis of co-exploration and co-production of coal measure gas. This work investigates the formation mechanism of various types of reservoirs (coalbed methane, shale gas, tight sandstone) in the Taiyuan Formation (Yushe-Wuxiang Block, eastern Qinshui Basin). Source rocks (coal seams and coal-measure mudstones) in the study area are characterized by type III kerogen, organic rich and over-mature, and reach a gas generation peak during the Early to Late Cretaceous. Coalbed methane mainly adsorbs on the surface of micropores, shale gas mainly occurs in micropores, macropores and micro-factures in adsorbed and free states, and tight sandstone gas mainly occurs in macropores in a free state. The combinations of successions are identified, coalbed methane, shale gas, and tight sandstone gas horizons are divided into a mudstone-sandstone reservoir (combination I), a coal-mudstone-sandstone reservoir (combination II), and a coal-mudstone reservoir (combination III). This division occurs from top to bottom in the succession and is identified on the basis of lithology, total organic carbon content (TOC) of mudstones, gas logging, superimposition relationships, and the source rock-reservoir-caprock assemblage. The strata thickness, continuity, and gas logging results of combination III comprise the most favorable conditions for fairly good development potential, followed by combination I. The development potential of combination II is poor due to the small strata thickness and poor continuity. The identification of superimposed reservoirs can provide an engineering reference for the exploration of coal-measure gas.

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“…Moreover, some vertical secondary faults are also observed at borehole Y1 (Figure 8). Numerical studies suggested that shale gas can easily escape through intensely deformed vertical fractures and faults [71,72], which might be the primary reason for the poor gas content in the borehole X1 and Y1. Therefore, we suggest that the MS can be considered a relatively stable tectonic region.…”

Section: Shale Gas Preservation In the Muganmentioning

confidence: 99%

“…Fourthly, tight strata and thrust faults can effectively prevent shale gas leakage, which is important factor for the preservation of shale gas that is evidenced by the Taiyang-Dazhai gas field and Jiaoshiba gas field [71,76,77]. The tight The thrust faults indicate that stress at the hanging wall is relatively concentrated by strong deformation.…”

Section: Shale Gas Preservation In the Muganmentioning

confidence: 99%

Tectonic Features of the Wufeng–Longmaxi Formation in the Mugan Area, Southwestern Sichuan Basin, China, and Implications for Shale Gas Preservation

et al. 2022

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Shale gas resources in mainland China and its commercial exploitation has been widely focused on the Wufeng–Longmaxi Formation organic-matter-rich shale in the Sichuan Basin. However, whether southwestern margin of the Sichuan Basin can produce high-quality shale gas has not been well resolved, which might be related to the poor understanding of the relationship between Cenozoic tectonic deformation and shale gas preservation. To answer the aforementioned scientific question, we conducted a detailed work in the Mugan area to show geologic structures and gas contents in the area through seismic profiles and geochemistry analysis. Specifically, the stable Mugan syncline shows a high gas content (>2.6 m3/t measured at three boreholes D1, D2, and D3), whereas its periphery presents a poor gas content (about 0.6 m3/t measured at two boreholes X1 and Y1). Moreover, oblique fracture density and dissolved pores are much higher at boreholes X1 and Y1 than that at the other three boreholes. We propose an opposite-verging thrust fault model to explain the different gas contents and tectonic features in the Mugan area, which might indicate that regions in the southwestern Sichuan Basin with similar tectonic and stratigraphic characteristics as those in the Mugan syncline are likely to produce high-yield shale gas. This finding provides new insights into the exploration theory of shale gas in the Tibetan Plateau.

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Structural deformation characteristics and shale gas preservation conditions in the Zhaotong National Shale Gas Demonstration Area along the southern margin of the Sichuan Basin

Cited by 13 publications

References 5 publications

Effect of Faults on Shale Pore Fracture and Shale Gas Preservation: A Case Study of the Wufeng-Longmaxi Formation in the Northeast Yunnan Area

Effect of Faults on Shale Pore Fracture and Shale Gas Preservation: A Case Study of the Wufeng-Longmaxi Formation in the Northeast Yunnan Area

A model for superimposed coalbed methane, shale gas and tight sandstone reservoirs, Taiyuan Formation, Yushe-Wuxiang Block, eastern Qinshui Basin

Tectonic Features of the Wufeng–Longmaxi Formation in the Mugan Area, Southwestern Sichuan Basin, China, and Implications for Shale Gas Preservation

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