Characteristics of in situ stress and its influence on coalbed methane development: A case study in the eastern part of the southern Junggar Basin, NW China

Fu, Hengzhi; Yan, Detian; Yang, Shenglai; Wang, Xiaoming; Zhang, Zheng; Sun, Mengdi

doi:10.1002/ese3.533

“…The seepage pressure was always less than the confining pressure to prevent water from flowing out between the heat‐shrinkable tube and the specimen. These test conditions were selected because, according to the actual in situ stress conditions and empirical formula in the study area, the horizontal in situ stress is approximately 10–20 MPa, and the seepage pressure is approximately 3 MPa within the depth range of the sample used in the test 35–37 . Different confining pressures and seepage pressures were selected to simulate different depth effects, and enough test data were obtained to understand the permeability evolution process of sandstone under different confining and seepage pressures.…”

Section: Equipment and Methodsmentioning

confidence: 99%

Experimental study on the mechanical properties, acoustic emission characteristics, and permeability evolution of sandstone under triaxial hydromechanical coupling

Wang

¹

,

Song

²

,

Wang

³

et al. 2022

Energy Science & Engineering

1

0

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In situ stress and groundwater have important effects on the deformation and stability of deep underground rock masses. Therefore, it is extremely important to study the mechanical properties and permeability evolutionary processes of rocks under hydromechanical (HM) coupling. The purpose of this study was to investigate the mechanical properties and permeability evolution of sandstone using triaxial compression tests under different confining and seepage pressures. The test results show that the confining pressure can increase the strength of sandstone, whereas the seepage pressure has the opposite effect. The initial and maximum permeabilities were positively correlated with seepage pressure and negatively correlated with confining pressure. The confining and seepage pressures had little effect on the change in initial permeability. As a common parameter of acoustic emission (AE), cumulative AE counts can intuitively reflect the permeability evolutionary process in the sandstone failure process. A permeability evolutionary early warning model for the sandstone failure process under HM coupling is proposed. The results are helpful for understanding the influence of in situ stress and seepage pressure on deep sandstone and the permeability evolutionary mechanism, and they can be used to provide early warning of water inrush disasters in deep underground structures.

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“…The permeability includes matrix permeability and fracture system permeability; the former is almost negligible, and the latter is the main factor to control the percolation conditions of the coal reservoir [44]. Permeability is mainly affected by geological factors such as stress field, burial depth, coal structure, and fractures [5,45].…”

Section: Permeability Variation With Depthmentioning

confidence: 99%

“…In situ stress is a type of internal stress in the Earth's crust, which is mainly controlled by gravity and tectonic activity [1][2][3][4][5]. Permeability is one of the important factors affecting the efficiency of coalbed methane (CBM) production.…”

Section: Introductionmentioning

confidence: 99%

In Situ Stress Distribution and Its Control on the Coalbed Methane Reservoir Permeability in Liulin Area, Eastern Ordos Basin, China

Feng

¹

,

Li

²

,

Tang

³

et al. 2021

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Permeability is one of the important factors that affect the production efficiency of coalbed methane, and it is mainly controlled by in situ stress. Therefore, it is very essential to study the in situ stress and permeability for the extraction of coalbed methane. Based on the injection/falloff well test and in situ stress measurement of 35 coalbed methane wells in the Liulin area in the east of the Ordos basin, the correlations between initial reservoir pressure, in situ stress, lateral stress coefficient, permeability, and burial depth were determined. Finally, the distribution characteristics of in situ stress and its influence on permeability were analyzed systematically. The results show that with the increase of burial depth, the initial reservoir pressure and in situ stress both increase, while the lateral stress coefficient decreases. The permeability variation is related to the type of stress field in different burial depths, and its essence is the deformation and destruction of coal pore structures caused by stress. The distribution characteristics of in situ stress at different depths and its effect on permeability are as follows: at depths < 800 m , the horizontal principal stress is dominant ( σ H ≥ σ v > σ h ) and the permeability is a simple decreasing process with the increase of the depth; at depths > 800 m , the vertical stress is dominant ( σ v ≥ σ H > σ h ). The permeability of most coal is very small due to the large in situ stresses in this depth zone. However, because of the stress release at the syncline axis, coal with high permeability is still possible at this depth zone. Due to the existence of high permeability data points at burial depth (>800 m) and the fitting relationship between permeability and vertical stress, the maximum and minimum horizontal principal stress is poor. However, the coal permeability and lateral stress coefficient show a good negative exponential relationship. This indicates that the lateral stress coefficient can be used to predict permeability better.

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“…In the aspect of coal properties, Wang et al (2018) and Zhang T et al (2021) studied the permeability anisotropy of high-dipping coals from the southern Junggar Basin based on laboratory experiments and numerical simulations. Li et al (2019) and Fu et al (2020) reported several datasets of in-situ stress from the eastern part of the southern Junggar Basin and discussed vertical permeability trends. Zhou et al (2016) and Li et al (2017) conducted experimental studies on the pore structure characteristics of coals in the southern Junggar Basin.…”

Section: Introductionmentioning

confidence: 99%

Coalbed methane accumulation, in-situ stress, and permeability of coal reservoirs in a complex structural region (Fukang area) of the southern Junggar Basin, China

Li

¹

,

Li²,

Pan³

et al. 2023

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The enrichment of coalbed methane (CBM), in-situ stress field, and permeability are three key factors that are decisive to effective CBM exploration. The southern Junggar Basin is the third large CBM basin in China but is also known for the occurrence of complex geological structures. In this study, we take the Fukang area of the southern Junggar Basin as an example, coalbed methane accumulation and permeability, and their geological controls were analyzed based on the determination of geological structures, in-situ stress, gas content, permeability, hydrology and coal properties. The results indicate that gas contents of the Fukang coal reservoirs are controlled by structural framework and burial depth, and high-to-ultra-high thickness of coals has a slightly positive effect on gas contents. Perennial water flow (e.g., the Baiyanghe River) favors gas accumulation by forming a hydraulic stagnant zone in deep reservoirs, but can also draw down gas contents by persistent transportation of dissolved gases to ground surfaces. Widely developed burnt rocks and sufficient groundwater recharge make microbial gases an important gas source in addition to thermogenic gases. The in-situ stress field of the Fukang area (700–1,500 m) is dominated by a normal stress regime, characterized by vertical stress > maximum horizontal stress > minor horizontal stress. Stress ratios, including lateral stress coefficient, natural stress ratios, and horizontal principal stress ratio are all included in the stress envelopes of China. Permeability in the Fukang area is prominently partitioned into two distinct groups, one group of low permeability (0.001–0.350 mD) and the other group of high permeability (0.988–16.640 mD). The low group of permeability is significantly formulated by depth-dependent stress variations, and the high group of permeability is controlled by the relatively high structural curvatures in the core parts of synclines and the distance to the syncline core. Meanwhile, coal deformation and varying dip angles intensify the heterogeneity and anisotropy of permeability in the Fukang area. These findings will promote the CBM recovery process in China and improve our understanding of the interaction between geological conditions and reservoir parameters and in complex structural regions.

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Characteristics of in situ stress and its influence on coalbed methane development: A case study in the eastern part of the southern Junggar Basin, NW China

Cited by 20 publications

References 41 publications

Experimental study on the mechanical properties, acoustic emission characteristics, and permeability evolution of sandstone under triaxial hydromechanical coupling

Experimental study on the mechanical properties, acoustic emission characteristics, and permeability evolution of sandstone under triaxial hydromechanical coupling

In Situ Stress Distribution and Its Control on the Coalbed Methane Reservoir Permeability in Liulin Area, Eastern Ordos Basin, China

Coalbed methane accumulation, in-situ stress, and permeability of coal reservoirs in a complex structural region (Fukang area) of the southern Junggar Basin, China

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