Factors controlling microfractures in black shale: A case study of Ordovician Wufeng Formation–Silurian Longmaxi Formation in Shuanghe Profile, Changning area, Sichuan Basin, SW China

Dong, Dazhong; Shi, Zhensheng; Sun, Shasha; Guo, Changmin; Zhang, Chenchen; Wen, Guo Chun; Guan, Quanzhong; Zhang, Mengqi; Jiang, Shan; Zhang, Leifu; Ma, Chao; Wu, Jin; Li, Ning; Yan, Cheng

doi:10.1016/s1876-3804(18)30085-5

Cited by 56 publications

(16 citation statements)

References 14 publications

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“…Combined with the basin geothermal evolution history, it can help to judge the uplift and subsidence process of the basin. , As the uplift process of the basins is mostly related to tectonic movement, the uniform temperature of fluid inclusions in fracture fillings has also been used to determine the fracture formation period in recent years. ,− However, how to use a variety of methods to verify each other, accurately determine the formation period of fractures, and finally establish the matching relationship between the formation time of natural fractures and hydrocarbon accumulation is the difficulty and focus of current fracture research. In the paper, taking the Changning area in the southern Sichuan Basin as an example, the development stages and evolutionary models of the fractures were determined based on geological methods, such as outcrop, drilling, and geophysical interpretation, combined with fracture filling inclusions, acoustic emission, and restoration of the burial–thermal evolution history. − …”

Section: Introductionmentioning

confidence: 99%

Formation Stages and Evolution Patterns of Structural Fractures in Marine Shale: Case Study of the Lower Silurian Longmaxi Formation in the Changning Area of the Southern Sichuan Basin, China

Fan

Zhao

et al. 2020

Energy Fuels

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Taking the Lower Silurian Longmaxi Formation in the Changning area of the southern Sichuan Basin as an example, the characteristics and formation stages of tectonic fractures are comprehensively studied by regional scale geological analysis and microscopic scale experimental tests. Regional scale geological analysis shows that there are mainly high-angle and vertical structural fractures, which have the characteristics of small opening, large spacing, small fracture density, and high filling degree. The fracture systems can be divided into three stages and six groups, which correspond to the structural compression in the near south−north, northwest, and northeast directions. The microscopic scale experimental test analysis confirmed that the formation of tectonic fractures mainly experienced three stages of tectonic movements, namely, the Middle−Late Yanshanian tectonic movement (136− 94 million years ago (Ma)), the Late Yanshanian tectonic movement−Early Himalayan tectonic movement (94−67 Ma), and the Middle−Late Himalayan tectonic movement (67−0 Ma). The corresponding uniform temperatures of the fracture filling inclusions are 118.5−140.2, 91.6−108.5, and 73.2−82.2 °C, respectively. Based on the tectonic analysis and geomechanical principles, an evolutionary model of structural fractures was established. Fractures with early formation and high filling degree and fractures with late formation but large angle between the fracture orientation and current geostress direction are beneficial to shale gas enrichment.

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Section: Introductionmentioning

confidence: 99%

Formation Stages and Evolution Patterns of Structural Fractures in Marine Shale: Case Study of the Lower Silurian Longmaxi Formation in the Changning Area of the Southern Sichuan Basin, China

Fan

Zhao

et al. 2020

Energy Fuels

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“…Formation and its periphery mainly shows two kinds of bedding: horizontal bedding and massive bedding, with bedding and nonbedding fractures [36][37][38][39]. Likewise, horizontal and massive bedding are also prevalent in the study area.…”

Section: Bedding Features the Shale Of The Wufeng-longmaximentioning

confidence: 99%

Influencing Factors of Shale Permeability in the Longmaxi Formation, Southern Sichuan Basin and Northern Yunnan-Guizhou Depression

Han

Liu

et al. 2022

Geofluids

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The current paper studies the influencing factors of permeability in shales of the Longmaxi Formation, located in the southern Sichuan Basin, China. The methodologies used in the present study include overburden pore permeability experiments, whole rock analysis and geochemical tests, NMR measurements of fluid saturation, pore size distribution and specific surface area distribution, SEM and extraction of pore structure parameters, and core analysis. The results show the following: (1) high TOC and high maturity generate a large number of organic pores, which may improve the permeability of shale. (2) Mineral composition and rock relative permeability also have influence on permeability to a certain degree, since different minerals have different effects on shale permeability. Clay in the study area has an adverse effect on permeability. The results show that the organic-rich siliceous clay mixed shale facies in this area has the best permeability. (3) A large specific surface area and total pore volume are associated with good shale permeability, while average pore size does not correlate with permeability. A small fractal dimension of pore morphology and simple pore structure result in good permeability, and bedding is the key controlling factor for the anisotropy of shale permeability. (4) Water in shales can influence the permeability of microfractures by binding to clay minerals. Low permeability in shales with high bound water saturation suggests that water and clay mineral absorption may block flow channels, resulting in poor permeability. The purpose of this study is to clarify the influencing factors on shale permeability of the Longmaxi Formation in the study area and to provide a reference for the exploration and development of shale gas in this area of the Sichuan Basin.

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“…Correspondingly, porosity distribution and permeability are also affected . Hence, maturation processes in shales change the microstructure properties of organic and inorganic constituents and possibly introduce bedding-parallel microcracks. , Weathering of shale outcrops can also result in changes in fracture properties.…”

Section: Comparison Based On Fracture Networkmentioning

confidence: 99%

Use of Outcrop as Substitute for Subsurface Shale: Current Understanding of Similarities, Discrepancies, and Associated Challenges

et al. 2021

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Full coring in shale reservoirs is challenging, time consuming, and risky due to fragility. Therefore, shale outcrop analogs are often used as an alternative to enhance the understanding of corresponding subsurface reservoir formation multifaceted mineralogy and rock characteristics. As consequence, many researchers perform their fundamental experimental studies on the core samples collected from outcrops when the subsurface unconventional shale samples are scarce. An assumption is often made that the rock composition and properties of outcrop and subsurface samples remain the same which raises some serious concerns and demands a thorough review of published research to check the validity of this approach to characterize shale reservoirs. The high degree of lateral and vertical heterogeneity and anisotropy, weathering, contamination, and postdepositional tectonic activities further add to the major challenges. In this literature-based study, the authors revisit the current understanding and challenges of using shale outcrops to complement the available subsurface samples and use them for the preliminary evaluation of underexploration and undeveloped unconventional shale reservoirs. The similarities and discrepancies of mineralogical, petrophysical, geochemical, and geomechanical properties are discussed. Finally, some concluding remarks and recommendations are presented.

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Factors controlling microfractures in black shale: A case study of Ordovician Wufeng Formation–Silurian Longmaxi Formation in Shuanghe Profile, Changning area, Sichuan Basin, SW China

Cited by 56 publications

References 14 publications

Formation Stages and Evolution Patterns of Structural Fractures in Marine Shale: Case Study of the Lower Silurian Longmaxi Formation in the Changning Area of the Southern Sichuan Basin, China

Formation Stages and Evolution Patterns of Structural Fractures in Marine Shale: Case Study of the Lower Silurian Longmaxi Formation in the Changning Area of the Southern Sichuan Basin, China

Influencing Factors of Shale Permeability in the Longmaxi Formation, Southern Sichuan Basin and Northern Yunnan-Guizhou Depression

Use of Outcrop as Substitute for Subsurface Shale: Current Understanding of Similarities, Discrepancies, and Associated Challenges

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