In-situ stress and permeability causality model of a low-rank coalbed methane reservoir in southwestern Ordos Basin, China

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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Characteristics of in-situ stress state and prediction of the permeability in the Upper Permian coalbed methane reservoir, western Guizhou region, SW China

Journal of Petroleum Science and Engineering ◽

10.1016/j.petrol.2018.02.037 ◽

2018 ◽

Vol 165 ◽

pp. 199-211 ◽

Cited By ~ 15

Author(s):

Wei Ju ◽

Zhaobiao Yang ◽

Yong Qin ◽

Tongsheng Yi ◽

Zhengguang Zhang

Keyword(s):

Stress State ◽

Coalbed Methane ◽

In Situ Stress ◽

Upper Permian ◽

Sw China ◽

Coalbed Methane Reservoir ◽

Western Guizhou

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EFFECTS OF IN-SITU STRESS AND JOINT ON PERMEABILITY OF THE COAL BED IN LINFEN BLOCK, SOUTHEASTERN ORDOS BASIN, CHINA

Геология и геофизика ◽

10.15372/gig20180308 ◽

2018 ◽

Keyword(s):

Ordos Basin ◽

In Situ Stress ◽

Coal Bed

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Principle of Well-Net Design for Coalbed Methane Exploitation in Coal Mine Area

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.543-547.3967 ◽

2014 ◽

Vol 543-547 ◽

pp. 3967-3973

Author(s):

Bao Shan Han

Keyword(s):

Coal Mining ◽

Coal Mine ◽

Coalbed Methane ◽

Design Theory ◽

Surface Condition ◽

Coal Pillar ◽

Negative Influence ◽

In Situ Stress ◽

Well Location

There are abundant CBM (Coalbed Methane) in China. These CBM has caused a remarkable problem to the coal-mining in China. In order to improve the structure of Chinese energy and eliminate the risk of coal mine gas, the relevant industries and sections have implemented many explorations in CBM enriched areas. With great achievements, there are many important problems in the actions of CBM exploitation. The disadvantageous interaction of the surface CBM well and the later coal mining has been ignored at all. There are many disadvantages and defects. To solve these problems and eliminate or weaken the disadvantageous, the scientific and reasonable design of surface CBM well location is an important step. With the thinking of surface condition, coal mining plan, the arrangement of coal mine laneway, the direction and scale of the in-situ stress, and thinking more about the negative influence to and of surface CBM well, according to the theories of mining dynamics, mining engineering, mining geomechanics, and the CBM engineering, the design theory of the surface CBM well net can be studied. Finally, the arrangement principle of CBM product well in coal field is presented. The existing or future coal pillar will be a critical location for the surface CBM well location.

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Geological and Gas-Content Features of Coalbed Methane System in Qinshui Basin, Shanxi

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.170-173.1187 ◽

2012 ◽

Vol 170-173 ◽

pp. 1187-1191

Author(s):

Ya Hui Jia ◽

Xiao Ping Xie ◽

Ai Li Lu

Keyword(s):

Coalbed Methane ◽

Gas Content ◽

Structural Deformation ◽

Shanxi Province ◽

Qinshui Basin ◽

The North ◽

North Part ◽

Coalbed Methane Reservoir ◽

High Yields

Colabed methane system is a natural system that consists of coal seams, coalbed methane in them and surrounding rocks. As an unconventional natural gas, reservoir and conservation of coalbed methane are different from those of conventional hydrocarbon. The Qinshui Basin, covering an area about 30,000sq.km in southeastern Shanxi Province, has abundant coalbed methane resources in the carboniferous Taiyuan formation and permian Shanxi formation, with an in-situ methane resource 3.3×1012 m3.In this study, the structural deformation and tectonic evolution of coalbed methane system in Qinshui basin were reported. Relationships between structural deformation and the formation of coalbed methane reservoir in Qinshui Basin were also discussed. The results show that Yangquan-Shouyang area in the north part of the basin and Tunliu-Xiangyuan area in the east are favorable for formation coalbed methane system. In contrast, Jincheng-Qinshui area in the south part of basin and the Qinyuan area in the middle of basin are favorable for both the formation of coalbed methane reservoirs and high yields as well.

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A Dual Fractal Poroelastic Model for Characterizing Fluid Flow in Fractured Coal Masses

Geofluids ◽

10.1155/2020/2787903 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

Guannan Liu ◽

Dayu Ye ◽

Feng Gao ◽

Jishan Liu

Keyword(s):

Fractal Dimension ◽

Pore Structure ◽

Coalbed Methane ◽

Coupling Effect ◽

In Situ Stress ◽

Permeability Model ◽

Fracture Length ◽

Coal Deformation ◽

Throat Diameter

In the process of coalbed methane exploitation, the fracture and pore structure is the key problem that affects the permeability of coalbed. At present, the coupling effect of fracture and pore structure and in situ stress is seldom considered in the study of coal seam permeability. In this paper, the fractal seepage model is coupled with coal deformation, and the adsorption expansion effect is considered. A multifield coupling model considering the influence of matrix and fracture structure is established. Then, the influence of pore structure parameters of main fracture on macropermeability is analyzed, including (1) fractal dimension of fracture length, (2) maximum fracture length, (3) fractal dimension of throat diameter, and (4) fractal dimension of throat bending. At the same time, the simulation results are compared with the results of Darcy’s uniform permeability model. The results show that the permeability calculated by the proposed model is significantly different from that calculated by the traditional cubic model. Under the action of in situ stress, when the porosity and other parameters remain unchanged, the macropermeability of coal is in direct proportion to the fractal dimension of coal fracture length, the fractal dimension of throat diameter, and the maximum fracture length and in inverse proportion to the fractal dimension of coal throat curvature.

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