Deep and ultra-deep natural gas exploration in the Sichuan Basin: Progress and prospect

Guo, Xusheng; Hu, Dongfeng; Huang, Rong; Wang, Zhihong; Duan, Jinbao; Wei, Xianjun; Fan, Xiaomeng; Miao, Zhiwei

doi:10.1016/j.ngib.2020.05.001

Cited by 49 publications

(47 citation statements)

References 5 publications

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“…During the Himalayan movement, the tectonic deformation in the Sichuan area was intense. Especially in the southern Sichuan area, all strata were pushed together, and the strata above Jurassic were almost completely eroded. , The formed faults became the key factor affecting the shale gas enrichment in the Sichuan Basin.…”

Section: Geological Settingsmentioning

confidence: 99%

Control of Complex Structural Deformation and Fractures on Shale Gas Enrichment in Southern Sichuan Basin, China

Shi

Tang

Wu³

et al. 2022

Energy Fuels

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The research on the differential enrichment mechanism of shale gas under the complex tectonic background is a key problem to be solved currently. The southern Sichuan Basin is taken as the research object, and the geochemical experiment, overburden porosity and permeability experiments, direction test of a ground stress experiment, and seismic interpretation method are used to clarify the structural deformation characteristics and fault characteristics under different structural styles and structural parts and summarize the differences of shale gas preservation critical conditions in different structural units. The results show that (1) the fracture level controls the boundary and scale of shale gas reservoirs. The primary/secondary faults within 3 km greatly influence shale gas reservoirs, and the complex combination of fault systems will cause obvious indigenous damage to shale gas reservoirs. (2) The angle between the fault strike and the direction of the maximum principal stress determines the sealing of the fault, and the angle greater than 45° can effectively inhibit the loss of shale gas. (3) The coupling effect of burial depth and dip angle controls the migration of shale gas along the strata. The greater the burial depth and the smaller the dip angle, the better the page sealing and preservation conditions. Based on the enrichment factors of shale gas in different tectonic units, three enrichment models of syncline, anticline, and slope are established, and the enrichment favorable areas are optimized, which has important guiding significance for shale gas exploration and development in Sichuan Basin.

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Section: Geological Settingsmentioning

confidence: 99%

Control of Complex Structural Deformation and Fractures on Shale Gas Enrichment in Southern Sichuan Basin, China

Shi

Tang

Wu³

et al. 2022

Energy Fuels

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“…Affected by episodes II and III of the Tongwan movement in the later Ediacaran, Member IV of the Dengying Formation has been denudated to variable extents in the study area. Consequently, it is thick in the northwest, thin in the southeast, and disappears westward from the Deyang–Anyue Sag (Guo et al, 2020; Ma, He, Cai, & Liu, 2017; Tian et al, 2019; Wen et al, 2020; Yang et al, 2020; You et al, 2020; Zhao et al, 2020; Zhu, Luo, Pang, Wen, & Jin, 2019). It has an overall thickness ranging between 260 and 350 m and contains four major lithofacies: light‐ to dark‐grey microbial dolostone, intraclastic dolostone, crystalline dolostone, and other dolostones with different components or formation mechanisms, such as siliceous, limy, and breccia dolostones.…”

Section: Geological Setting and Stratigraphymentioning

confidence: 99%

Microbial carbonate sequence architecture and depositional environments of Member IV of the Late Ediacaran Dengying Formation, Gaoshiti–Moxi area, Sichuan Basin, Southwest China

et al. 2021

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The recent discovery of the Anyue gas field, with huge reserves, has great potential for ultradeep gas production in carbonate reservoirs. Previous exploration and exploitation of Member IV of the Dengying Formation in the Gaoshiti–Moxi area deposited during the Late Ediacaran have provided useful insight into palaeo‐gas reservoirs, and geological significance of the Precambrian microbial carbonate strata. In this study, the depositional sequence architecture has been established and typical environments from Member IV of the Dengying Formation in the Gaoshiti–Moxi area have been reconstructed through detailed sedimentological analysis of cores, petrophysical data, well‐logging data and seismic interpretation. One third‐order sequence was identified, which is subdivided into seven fourth‐order sequences and 18–19 fifth‐order sequences. The third‐order sequence is bounded by denudation surfaces or onlap surfaces, and composed of transgressive system tracts and highstand system tracts. The fourth‐order sequences are bounded by instantaneously exposed punctuated surfaces or lithology and lithofacies transition surfaces, featured by specific lithological cycles, such as ‘lower microcrystalline dolomite, middle intraclastic dolomite and sparry thrombolite, and upper intraclastic dolomite’, ‘middle–lower sparry thrombolite and upper microcrystalline dolomite and sparry thrombolite’, ‘lower micritic thrombolite, middle micritic dolomite, and upper sparry thrombolite and laminites’, and ‘lower microcrystalline dolomite, middle intraclastic dolomite and argillaceous or micritic dolomite, and upper intraclastic dolomite’. The sequence characteristics reveal that periodic high‐frequency sea‐level change and palaeogeomorphology are controlling factors affecting sequence development, which lay a significant foundation for reservoir development. During the depositional period, a tidal flat on a restricted carbonate platform is well‐developed, allowing the identification of 16 microfacies, 13 microfacies associations, and 6 seismic facies. Inter‐lower tidal flats are widely developed with band‐shaped mound–bank complex, microbial mound, and shoal on the platform margin. On the inner platform, patchy microbial mounds, mound–flat combinations, and inter‐shoal/microbial mounds are developed in the Gaoshiti area, whereas patchy shoals and shoal–flat combinations are developed in the Moxi area. During the early depositional period of Member IV of the Dengying Formation, the microbial mounds and shoals were developed on the platform margin. The dolomitic flat and inter‐shoal/microbial mounds are mainly developed on the inner platform with little microbial mound and shoal deposition. During the late depositional period of Member IV of the Dengying Formation, large‐scale microbial mounds and shoals are sustainably and stably developed on the platform margin; enlarged dolomitic flat, patchy microbial mounds, and patchy shoals are predominantly developed in the platform interior with inter‐shoal/microbial mounds dying out.

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“…To meet the increasing demand for natural gas, oil companies in China have gradually shifted the focus of shale gas exploration and development to deep shale formations (with burial depths of 3500–4500 m, referred to as deep shale reservoirs in this work) or even ultradeep shale formations (with burial depths greater than 4500 m). The deep-ultradeep shale gas reservoirs in the Sichuan Basin and its surrounding areas have stable thicknesses and are widely distributed . It is estimated that the gas resource for shale reservoirs with burial depths of 3500–6000 m accounts for more than 70% of the total shale gas reserves, showing a great gas potential for deep shale reservoirs in the Sichuan Basin and its surrounding areas…”

Section: Introductionmentioning

confidence: 99%

“…The deep-ultradeep shale gas reservoirs in the Sichuan Basin and its surrounding areas have stable thicknesses and are widely distributed. 2 It is estimated that the gas resource for shale reservoirs with burial depths of 3500− 6000 m accounts for more than 70% of the total shale gas reserves, showing a great gas potential for deep shale reservoirs in the Sichuan Basin and its surrounding areas. Shale gas reservoir is a typical self-generating and self-storage system, in which free gas mainly stores in the pore−fracture network of shale, and adsorbed gas occurs on the surface of organic matter (OM) or clay minerals.…”

Section: Introductionmentioning

confidence: 99%

Characteristics and Influencing Factors of Supercritical Methane Adsorption in Deep Gas Shale: A Case Study of Marine Wufeng and Longmaxi Formations from the Dongxi Area, Southeastern Sichuan Basin (China)

Wang

Jia

et al. 2022

Energy Fuels

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Deep shale reservoirs with burial depths of >3500 m are now the target of gas producing intervals in the Sichuan Basin, China. Due to the in situ high temperatures and pressures, methane in deep shale formations is supercritical, resulting in the inapplicability of some conventional adsorption models. To determine the methane adsorption capacity of deep shale and its influencing factors, different shale lithofacies from the Dongxi area of the southeastern Sichuan Basin are investigated and compared in this work. The nanopore structure of Wufeng (WF) and Longmaxi (LMX) gas shales are characterized using gas (nitrogen and carbon dioxide) physisorption and high-resolution scanning electron microscopy (SEM). Methane isothermal adsorption experiments are carried out on typical shale samples at different temperatures (from 30 to 90 °C) and pressures (up to 32 MPa). The excess adsorption data are fitted by the supercritical Dubinin–Radushkevich (SDR) model, and the dominant influencing factors of methane adsorption in deep marine shale are determined. Four shale lithofacies are recognized in the study area, including silica-rich argillaceous shale (CM-1), siliceous shale (S), clay-rich siliceous shale (S-3), and argillaceous–siliceous mixed shale (M-2). Nanoscale organic matter (OM) pores, often in irregular, angular and flat shapes, are the dominant pore types in the WF and LMX shale samples. Generally, the pore size spectrum of OM pores is shale lithofacies dependent, e.g., 10–160 nm for S shale and 10–120 nm for CM-1 shale. Compared to other shale lithofacies, S shale exhibits the highest methane adsorption capacity, followed by M-2 shale, while CM-1 shale has the smallest methane adsorption capacity. The adsorption capacity of methane for deep WF and LMX shales is positively correlated with the total organic carbon (TOC) content, micropore volume, and micropore specific surface area. Absolute methane adsorption capacity of deep shale increases with the increase of pressure, but it will decrease at a higher temperature due to the negative and predominant effect of temperature on methane adsorption. The higher TOC content and more abundant small-sized pores promote the S shale to have the strongest adsorption capacity for methane molecules; this indicates that S shale is the most beneficial shale lithofacies for gas adsorption.

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Deep and ultra-deep natural gas exploration in the Sichuan Basin: Progress and prospect

Cited by 49 publications

References 5 publications

Control of Complex Structural Deformation and Fractures on Shale Gas Enrichment in Southern Sichuan Basin, China

Control of Complex Structural Deformation and Fractures on Shale Gas Enrichment in Southern Sichuan Basin, China

Microbial carbonate sequence architecture and depositional environments of Member IV of the Late Ediacaran Dengying Formation, Gaoshiti–Moxi area, Sichuan Basin, Southwest China

Characteristics and Influencing Factors of Supercritical Methane Adsorption in Deep Gas Shale: A Case Study of Marine Wufeng and Longmaxi Formations from the Dongxi Area, Southeastern Sichuan Basin (China)

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