Fluid velocity sensitivity of coal reservoir and its effect on coalbed methane well productivity: A case of Baode Block, northeastern Ordos Basin, China

A discrete element numerical model simulating the process of gas pressurization in coalbed methane wells is built based on UDEC software. The model considers the unique vertical fracture system of the coal. Simulates the distribution of effective stress, pore pressure and the node displacement vector around the wellbore in the process of pressurization under different terrestrial stress conditions. The analysis shows that, reservoir fluid flow and matrix deformation in the pressurization of cavity completion can be better represented by taking coal's unique fracture system into consideration. Coal reservoir with anisotropic stress is more prone to rupture and collapse than that under isotropic condition. In the vertical fracture system, the discrepancy of the fluid velocity will lead to differences in formation stress gradient and help generate shearing fracture. Tensile fractures’ formation and growing trend can be reflected by nodal displacement vector distribution.

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Macrolithotype characteristics of coal seam and their controls on coalbed methane well productivity in the Hancheng block of the southeastern margin of Ordos Basin

Energy Sources Part A Recovery Utilization and Environmental Effects ◽

10.1080/15567036.2020.1772910 ◽

2020 ◽

pp. 1-14

Author(s):

Tiantian Zhao ◽

Hao Xu ◽

Dazhen Tang ◽

Yulong Liu

Keyword(s):

Coal Seam ◽

Coalbed Methane ◽

Ordos Basin ◽

Well Productivity ◽

Southeastern Margin

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Characterization of fines produced during drainage of coalbed methane reservoirs in the Linfen block, Ordos Basin

Energy Exploration & Exploitation ◽

10.1177/0144598720935528 ◽

2020 ◽

Vol 38 (5) ◽

pp. 1664-1679

Author(s):

Aoxiang Zhang ◽

Daiyong Cao ◽

Yingchun Wei ◽

Thomas E Rufford

Keyword(s):

Coalbed Methane ◽

Fine Particles ◽

Ordos Basin ◽

Particle Size Analysis ◽

Size Analysis ◽

Burial Depth ◽

Main Components ◽

Coal Reservoir ◽

Casing Pressure ◽

Coal Fines

Coal fines produced during drainage of coalbed methane reservoirs can affect the permeability of the coal reservoir and damage production facilities such as downhole pumps, shafts, and valves. Thus, to clarify the mechanism of coal fines output is very important to high production of coalbed methane. The characteristics of coal fines can be used to identify the sources of the coal fines and to develop reasonable means of controlling coal fines output. In this study, different coal fines characteristics were investigated to reveal the output mechanism of coal fines. The coal fines samples were collected from 16 coalbed methane wells, which located in Eastern Ordos Basin of China. And the wells are in different drainage stages. The coal fines samples were analyzed by using transmission light microscopy, reflection polarized optical microscopy, laser particle size analysis, X-ray diffraction, and scanning electron microscopy with energy dispersive X. The results show that the concentration of coal fines is in the range of 3–8% (volume percent). The sizes of the coal fine particles tended to be below 200 µm. The main components of pulverized coal are vitrinite and inorganic minerals and the average content of inorganic minerals account for 50.56% and the standard deviation is 0.0685. The morphology analysis results show that the shape of coal fines is different in different parts of the coalbed methane wells. The coal fines concentration increases with the increase in the thickness of the deformed coal, and decreases with the increase in the burial depth. The concentration of coal fines becomes higher with the increase of casing pressure and coal fines concentration increases with the increase of the variation of bottom hole pressure.

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Evaluation of the coal reservoir permeability using well logging data and its application in the Weibei coalbed methane field, southeast Ordos basin, China

Arabian Journal of Geosciences ◽

10.1007/s12517-014-1661-y ◽

2014 ◽

Vol 8 (8) ◽

pp. 5449-5458 ◽

Cited By ~ 4

Author(s):

Taotao Yan ◽

Yanbin Yao ◽

Dameng Liu ◽

Yadong Bai

Keyword(s):

Coalbed Methane ◽

Ordos Basin ◽

Well Logging ◽

Reservoir Permeability ◽

Coal Reservoir

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Analysis of the Physical Characteristics of Coal Reservoir in Hancheng Mining Area, Ordos Basin, China

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.737.805 ◽

2015 ◽

Vol 737 ◽

pp. 805-808

Author(s):

Yan Hui Yang ◽

Qi Lu Xu

Keyword(s):

Coalbed Methane ◽

Alternative Energy ◽

Ordos Basin ◽

Physical Property ◽

Mining Area ◽

Test Results ◽

Throat Radius ◽

Unconventional Natural Gas ◽

Is Development ◽

Coal Reservoir

<p>Coalbed methane (CBM) which is a kind of efficient and clean unconventional natural gas will be the alternative energy in the future. The studying degree of predecessor is low to the pore-fracture structures of coal reservoir in Hancheng Mining area, Ordos Basin, China. It has been researched with some tests and the results are as follows: micropore is more, specific surface area is larger, throat radius is lesser, permeability is low, but the pore - fracture is development, phenomenon of mineral filling pore - fracture is widespread, sorting features of throat radius is better. From the point of test results, physical property of coal reservoir in the study area is good,which is suitable for the exploration and development of coalbed methane resources.</p>

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A Comprehensive Coal Reservoir Classification Method Base on Permeability Dynamic Change and Its Application

Energies ◽

10.3390/en13030644 ◽

2020 ◽

Vol 13 (3) ◽

pp. 644 ◽

Cited By ~ 2

Author(s):

Xinlu Yan ◽

Songhang Zhang ◽

Shuheng Tang ◽

Zhongcheng Li ◽

Yongxiang Yi ◽

...

Keyword(s):

Coalbed Methane ◽

Dynamic Change ◽

Initial Permeability ◽

Gas Production ◽

Gas Desorption ◽

Reservoir Permeability ◽

Geological Conditions ◽

Production Stages ◽

Productivity Potential ◽

Coal Reservoir

Due to the unique adsorption and desorption characteristics of coal, coal reservoir permeability changes dynamically during coalbed methane (CBM) development. Coal reservoirs can be classified using a permeability dynamic characterization in different production stages. In the single-phase water flow stage, four demarcating pressures are defined based on the damage from the effective stress on reservoir permeability. Coal reservoirs are classified into vulnerable, alleviative, and invulnerable reservoirs. In the gas desorption stage, two demarcating pressures are used to quantitatively characterize the recovery properties of permeability based on the recovery effect of the matrix shrinkage on permeability, namely the rebound pressure (the pressure corresponding to the lowest permeability) and recovery pressure (the pressure when permeability returns to initial permeability). Coal reservoirs are further classified into recoverable and unrecoverable reservoirs. The physical properties and influencing factors of these demarcating pressures are analyzed. Twenty-six wells from the Shizhuangnan Block in the southern Qinshui Basin of China were examined as a case study, showing that there is a significant correspondence between coal reservoir types and CBM well gas production. This study is helpful for identifying geological conditions of coal reservoirs as well as the productivity potential of CBM wells.

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