Mineral Composition of Prospective Section of Wufeng-Longmaxi Shale in Luzhou Shale Play, Sichuan Basin

Yang, Haining; Shi, Xuewen; Luo, Chao; Wu, Wei; Li, Yi; He, Yifan; Zhong, Kesu; Wu, Jianguo

doi:10.3390/min12010020

Cited by 7 publications

(3 citation statements)

References 39 publications

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“…The southern Sichuan Basin, including Luzhou, Western Chongqing, Weiyuan, and Changning blocks, is an important target area for the exploration and development of deep shale gas (with a burial depth of 3500–4500 m) in China. , In this study, 17 shale cores were obtained from the Luzhou block (wells L206, L203H153-8, Y101H88-1, and Y101H53-3) and Western Chongqing block (wells Zu203 and H202H2-1) located at the southern Sichuan Basin (Figure ). The samples were collected from the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation.…”

Section: Experiments and Methodsmentioning

confidence: 99%

Storage Capacity and Microdistribution of Pore Water in Gas-Producing Shales: A Collaborative Evaluation by Centrifugation and Nuclear Magnetic Resonance

Li,

Zhou,

Wang

et al. 2023

Energy Fuels

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Both adsorbed and free water occur in shale matrix pores and intensely impact methane accumulation and transport in a shale gas reservoir. As a result of multiple water coexistence in complicated nanoporous shale, there still is a large challenge for the determination of the storage capacities and microdistributions of adsorbed and free water. In this study, storage characteristics of adsorbed and free water in deep gas-producing shales from the southern Sichuan Basin of China were investigated using a collaborative evaluation of centrifugation and nuclear magnetic resonance (NMR) under atmospheric pressure and 30 °C temperature conditions. Results show the following: (1) The amounts of adsorbed and free water in water-saturated shales are 1.7967−16.0964 mg/g (mean of 9.3875 mg/g) and 6.4267−19.8020 mg/g (mean of 11.0377 mg/g), respectively. The adsorbed water accounts for 15.83−66.10 wt % (mean of 45.14 wt %) of total water. Adsorbed water mainly exists in pores developed in solid bitumen and clay mineral. More free water is stored in the pores of solid bitumen than that in clay mineral-related pores. (2) The adsorbed water primarily distributes in pores of <20 nm; in contrast, the free water is mainly stored in >2 nm pores. The microdistributions of adsorbed and free water were controlled by the pore size distribution in shales. The mass ratio of adsorbed water decreases with increasing the pore size. (3) The presence of adsorbed water implies that some of water stored in matrix pores cannot flow. The free water is a potential source of the flowback fluid of the shale gas well. This study not only provides an evaluation theory and method but also contributes to insight into the gas−water storage in shale pores.

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Section: Experiments and Methodsmentioning

confidence: 99%

Storage Capacity and Microdistribution of Pore Water in Gas-Producing Shales: A Collaborative Evaluation by Centrifugation and Nuclear Magnetic Resonance

Li,

Zhou,

Wang

et al. 2023

Energy Fuels

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“…Fracture Morphology of Shale. From the relationship between the mineral composition and mechanical parameters Quartz, the most important brittle mineral of the lower submember of the first member of the Longmaxi Formation in the Luzhou area of the Sichuan Basin, 27 has a higher hardness and lower plasticity than calcite, and consequently, the fracture morphologies are different between the samples with quartz as the main brittle mineral and the samples with calcite as the main brittle mineral, as shown in Figure 8. In this figure, panel (a) is a shale sample with quartz as the primary brittle mineral, and panel (c) is a shale sample obtained from the Wufeng Formation, with a calcite content as high as 61%.…”

Section: Effect Of Minerals On Rock Mechanics Andmentioning

confidence: 99%

Effects of Mineral Composition and Lamina on Mechanical Properties and Fractures of the Wufeng–Longmaxi Shale in the Luzhou Area of the Southern Sichuan Basin

Luo,

Yan,

Zheng

et al. 2023

Energy Fuels

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Because natural fractures are crucial for the hydraulic stimulation and development of the fracture network of a shale gas reservoir, understanding the influence of mineral composition and lamination on the occurrence of fracture and mechanical properties of shale is significant. To clarify the influence of mineral composition and lamination on the occurrence and mechanical properties of shale, combined analyses of X-ray diffraction, uniaxial compression, triaxial compression, and rock slice were performed on shale samples obtained from the lower submember of the first member of the Longmaxi Formation in the Luzhou area of the Sichuan Basin. After compression testing, the mineral characteristics and fracture morphologies of the Luzhou shale were analyzed based on the results and the characteristics of rock mechanics and fractures of the Luzhou shale owing to different mineral compositions and laminar development characteristics were summarized. The mineral composition of the shale in the study area primarily comprised quartz, feldspar, calcite, and clay minerals. Under uniaxial compression, the mechanical property, Young’s modulus, exhibited a positive correlation with the quartz content. The compression of the shale samples produced one to two shear fractures running through them, and the secondary fractures produced small angles around the main fractures or developed along the laminae. The laminated layer enhanced shale anisotropy and fracture trapping abilities. Although the oblique intersection of fractures at 45° along the laminated direction can produce and develop cracks more along the laminated direction than along the vertical direction, the high clay content of the shale will weaken this phenomenon. In summary, the commonly available shale was classified into four types based on its mineral content and the degree of lamination development; the commonly available high-quality shale has high brittleness and developed laminae. This study contributes to a better understanding of the rock mechanics and fracture evaluation of shale reservoirs.

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“…The WF–LMX section in southern Sichuan comprises deep‐water continental shelf facies of dark grey and black siliceous and carbonaceous shales known for their high organic carbon (OC), gas content and OM pores (Ma et al, 2020; Wang et al, 2019). Formations outcropping on the surface within the Luzhou block are, from the youngest to the oldest, of the Quaternary, Cretaceous, Jurassic and Triassic Periods, with the Jurassic formations being the predominant type and the Triassic and Quaternary formations appearing sporadically (Yang et al, 2021). Analysis of the drilling data obtained from wells such as Y101 and L208 reveals an unconformable contact between the Silurian formations and the overlying Liangshang Fm, between the Maokou Fm and the overlying Longtan Fm, and between the Jialingjiang Fm and the overlying Xujiahe Fm, along with a normal stratigraphic sequence for the remaining formations.…”

Section: Geological Settingmentioning

confidence: 99%

Intensive geological alteration and gas accumulation in Longmaxi Formation shales at moderate and great depths: A case study of the Luzhou area in the southern Sichuan fold zone, China

Jiang¹,

Tang²,

Zhong³

et al. 2023

Geological Journal

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In recent years, significant efforts have been directed towards extracting deep shale gas (SG) in Luzhou. Understanding the factors influencing the accumulation and preservation of SG in the section extending from the Upper Ordovician Wufeng (WF) Formation (Fm) through the Lower Silurian Longmaxi (LMX) Fm is crucial for its large‐scale, profitable development. The shale layers in the LMX Fm located in the Luzhou‐Zigong area in the southern part of the Sichuan Basin have undergone unique geological processes, including deep deposition, intensive uplift, erosion and deformation. The Luzhou block, situated in the low‐fold zone in southern Sichuan between the southern slope of the paleo‐uplift in central Sichuan and the down‐warping fold zone in south‐eastern Sichuan, was studied using seismic, well‐log, drilling and core analysis and test data to understand its tectonic, sedimentary, reservoir and fracture characteristics and identify the principal factors controlling gas accumulation in this area. The study found that SG in the Luzhou block is primarily distributed in the WF Fm through the Longyi1 sub‐member. Class I continuous reservoirs, 2.6–20.3 m in thickness, are mainly found in the Longyi11–13 sublayers and those with large continuous thickness produced high yields during tests. Gentle anticlinal zones and wide, gentle tectonic structures with relatively high‐pressure coefficients have formed in this area. High‐angle fractures (HACs) in this area tend to accumulate free gas and, therefore, facilitate the accumulation and production of SG. The study concludes that the continuous thickness of Class I reservoirs and natural HACs controlled by the centre of the deep‐water continental shelf are the primary factors controlling SG accumulation in the Luzhou block.

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Mineral Composition of Prospective Section of Wufeng-Longmaxi Shale in Luzhou Shale Play, Sichuan Basin

Cited by 7 publications

References 39 publications

Storage Capacity and Microdistribution of Pore Water in Gas-Producing Shales: A Collaborative Evaluation by Centrifugation and Nuclear Magnetic Resonance

Storage Capacity and Microdistribution of Pore Water in Gas-Producing Shales: A Collaborative Evaluation by Centrifugation and Nuclear Magnetic Resonance

Effects of Mineral Composition and Lamina on Mechanical Properties and Fractures of the Wufeng–Longmaxi Shale in the Luzhou Area of the Southern Sichuan Basin

Intensive geological alteration and gas accumulation in Longmaxi Formation shales at moderate and great depths: A case study of the Luzhou area in the southern Sichuan fold zone, China

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