Influence of the Emeishan basalt eruption on shale gas enrichment: A case study of shale from Wufeng-Longmaxi formations in northern Yunnan and Guizhou provinces

Yan-jun, LI; Li, Minglong; Zhang, Jiehui; Pang, Qian; Zou, Chunxia; Shu, Honglin; Wang, Gaoxiang

doi:10.1016/j.fuel.2020.118835

Cited by 15 publications

(21 citation statements)

References 20 publications

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“…The activity of the mantle plume in Emeishan during the Late Permian resulted in the massive eruption of Emeishan basalt, which gradually thinned from the Xiaojiang fault to the east and gradually pinched out in the Gongxian area. Although it had no direct impact and no re-formation on the Wufeng-Longmaxi Formation, it resulted in a high geothermal field, which promotes the thermal evolution of OM . The OM maturity, R 0 , of the study area is between 2.2 and 2.7%, which is not considerably different from the adjacent area. , …”

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 Indosinian-Yanshanian tectonic movement often produced NE-SW trending structures, while the Himalayan movement produced NS or NW-SE trending structures. Structurally, the Indosinian-Yanshanian tectonic movement produced similar folds in the southwest and southern Sichuan Basin, e.g., anticlines generally exhibit high and steep dip angles, whereas synclines exhibit wide and gentle dip [21,22,65,66]. Although the anticlines in the Mugan area were influenced by fault deformation associated with the Cenozoic tectonic movement, its geometry appears to be consistent with that in the southern Sichuan Basin.…”

Section: Shale Gas Preservation In the Muganmentioning

confidence: 77%

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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“…This member is rich in paleontological fossils such as graptolite, with silty bands at its top. The Longmaxi-2 Member is composed of grey and grey-green shale, with many silty bands and a few graptolites [28,29]. The Longmaxi-1 Member is divided into the underlying Longmaxi-1 1 Submember and the overlying Longmaxi-1 2 Submember by lithological characteristics.…”

Section: Geological Settingmentioning

confidence: 99%

Sedimentary Facies of the Longmaxi Formation Shale Gas Reservoir in the Weiyuan Area Based on Elemental Characteristics

Tang

Wang

et al. 2021

Geofluids

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The Lower Silurian Longmaxi Formation in the southern Sichuan Basin is composed of a series of dark carbonaceous shales deposited in a hydrostatic shelf reduction environment. In this study, the ratio of uranium to thorium (U/Th), the total organic carbon (TOC), and the biological silicon content (SiBio) were selected as the characteristic parameters to precisely analyze the sedimentary environment and its impact on reservoir quality. The results show that the Weiyuan area in the Early Silurian Longmaxi period experienced two transgression-regression cycles, forming two third-class sequences, SSQ1 and SSQ2, which can be divided into six sedimentary microfacies: organic-rich siliceous argillaceous shelf, organic-rich silicon-containing argillaceous shelf, organic-rich silty argillaceous shelf, deep-water silty argillaceous shelf, shallow-water silty argillaceous shelf, and shallow-water argillaceous silty shelf microfacies. The organic-rich siliceous argillaceous shelf and organic-rich silicon-containing argillaceous shelf microfacies developed in the deepest transgressive system tract (TST1), with high U/Th, high TOC, and high SiBio, which are identified as the main control facies for reservoir development. These two microfacies are located in the middle of the study area, while a transition occurs in the east affected by the Neijiang Uplift. According to the classification criteria proposed in this article, the favourable shale gas reservoirs in Weiyuan area are characterized with high U/Th (>1.25), high TOC (>3%), and high SiBio (>15%). This paper proposed an evaluation method for shale sedimentary facies based on elemental and electrical logging characteristics, avoiding the limitations of core samples, which makes the quantitative division of shale sediments and the efficient recognition of high-quality reservoirs available. It is of great significance for delineating the potential production areas in the study area and beneficial for the scaled development of shale gas reservoirs.

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Influence of the Emeishan basalt eruption on shale gas enrichment: A case study of shale from Wufeng-Longmaxi formations in northern Yunnan and Guizhou provinces

Cited by 15 publications

References 20 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

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

Sedimentary Facies of the Longmaxi Formation Shale Gas Reservoir in the Weiyuan Area Based on Elemental Characteristics

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