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Jincheng, China

Guo H.-Y.,Henan Polytechnic University | Luo Y.,Henan Polytechnic University | Ma J.-Q.,Henan Polytechnic University | Xia D.-P.,Henan Polytechnic University | And 2 more authors.
Meitan Xuebao/Journal of the China Coal Society | Year: 2014

In order to study the effect of permeability increase via microbial treatment on different-rank coals and its mechanism, different coal samples were collected for the bio-methane simulation experiment, in which instruments like optical microscope and mercury-injection apparatus and techniques including FTIR and XRD were utilized to test and analyze the varying characteristics respectively on the surface pores and fractures, pore structures, functional groups and microcrystalline structures of coal samples before and after bio-methane metabolism. The experimental results show that the number, length and width of surface pores and fractures of polished section of coal all saw an increase after biomethane metabolism. The pore volume of coal samples increase significantly, the connectivity is enhanced and pore structure is improved, whereas the specific surface area of pore decreases. While the oxygen-containing functional groups of coal increase, the aromatic rings are opened gradually. Also the hydroxyl is introduced to the split parts and its content increases. With the aromatic carbon layer distance(d002) increases, the number of aromatic layer (Nc), packing degree (Lc) and elongation (La) decrease accordingly. Bio-methane metabolism not only can use coal as a carbon source to produce methane further to increase coalbed methane resources but also can improve the pore structure of coal, increase the reservoir permeability and reduce the specific surface area of coal for the coalbed methane desorption, which is of great engineering significance for coalbed methane development. Source


Zhang Z.,China University of Mining and Technology | Qin Y.,China University of Mining and Technology | Bai J.,Shanxi Lanyan CBM Group Co. | Fu X.,China University of Mining and Technology | Liu D.,China University of Mining and Technology
Energy Exploration and Exploitation | Year: 2016

The coalbed methane resources in the Taiyuan Formation account for 55% of total coalbed methane reserves in the southern Qinshui Basin, China; however, the resources have yet to be utilized basically. The joint exploitation of coalbed methane in the Taiyuan Formation and the Shanxi Formation can accelerate the process of coalbed methane scale development in this region. The productivity characteristics of commingling drainage are controlled by various geological factors. Thus, to select favorable regions for multi-seam coalbed methane joint exploitation, the impacts of some geological factors such as coal thickness, burial depth, gas content, reservoir pressure gradient, and reduced water level on the gas production were analyzed and estimated based on a bivariate correlation analysis. Analysis results show that the two coal seams of the high production rate wells of commingling drainage usually have the following conditions: total coal thickness >9.5 m; average burial depth <640 m; average gas content >14m3/t; reservoir pressure gradient difference <0.05 MPa/100 m; reduced water level difference <55 m. Based on the correlation analysis results, the potential of multi-seam coalbed methane exploitation in the study area was evaluated by using a multi-objective fuzzy matter-element model. At last, taking the evaluation coefficient 0.75 as the critical value, unfavorable zones, relatively favorable zones, favorable zones, and extremely favorable zones for multi-seam coalbed methane joint exploitation were identified in the southern Qinshui Basin. © The Author(s) 2016. Source


Tian Y.-D.,State Energy Key Laboratory of Joint Exploitation of Coal and Coal bed Methane | Tian Y.-D.,Shanxi Lanyan CBM Group Co. | Wu J.,Shanxi Lanyan CBM Group Co. | Wu J.,Shanxi Province Key Laboratory of Coal and Coalbed Methane Simultaneous Extraction
Meitan Xuebao/Journal of the China Coal Society | Year: 2014

In order to achieve a high-efficient exploitation of CBM in the southern Qinshui Basin, the velocity sensitivity, water sensitivity, alkaline sensitivity and stress sensitivity of the main coalbed 3 were investigated and analysed. The results show that: the degree of velocity sensitivity damage at the coalbed 3 varies from medium to weak. In the actual CBM development process, the velocity sensitivity damage is due to the transportation of coal powder produced by the coalbed washout of the fracturing fluid containing sand. The degree of water sensitivity damage at the coalbed 3 varies from medium to weak. Adding a small amount of KCl to the working fluid can reduce the water sensitivity effect. The coalbed 3 is a weak alkaline sensitive reservoir, however, the high pH fluids will dissolve quartz sand and reduce the support effect. The coalbed 3 is a strong stress sensitivity reservoir. According to the comparison of permeability change in the step-up and step-down phases, the irreversible damage rate is 55.88%. In the coalbed methane development process, in theory, strengthening reservoir protection can increase the coalbed methane production. Source


Meng Z.-P.,China University of Mining and Technology | Meng Z.-P.,China Three Gorges University | Liu S.-S.,China University of Mining and Technology | Wang B.-Y.,Shanxi Lanyan CBM Group Co. | And 2 more authors.
Meitan Xuebao/Journal of the China Coal Society | Year: 2015

Adsorption capacity of coals is a main reservoir parameter to determine the amount of gas-bearing and exploitive potential in coal seams. To determine the adsorption capacity of coal to methane under different temperatures and pressures related to coal body structures, isothermal adsorption experiments were conducted with four high-rank coal samples of different coal body structures, which were selected from No.3 Shanxi Formation (Permian) coal seam of Zhaozhuang coal mine in south-eastern Qinshui basin. To reveal the control mechanism of porous structure to CBM (coal bed methane) adsorption from microcosmic level, low-temp liquid nitrogen adsorption-desorption experiments on various coal body structure coals were conducted. The results show that coal adsorption to methane is in accordance with Langmuir equation. Saturated adsorption volume increases with the increase of coal deformation degree while decreases with the temperature increase. Pore specific surface area and pore volume increase with the increase of deformation degree in coal body. Wherein, pore volume is mainly dominated by mesopores while pore specific surface area is largely contributed by adsorption pores. Mylonitized coal has the maximum size of pore specific surface area and pore volume under various pore diameters, which is followed by the granulated coal, calaclastic coal and intact coal. The rule concluded is in consistent with that of isothermal adsorption test, indicating that CBM content is higher in area with greater deformed coals under the same geological conditions. ©, 2015, Meitan Xuebao/Journal of the China Coal Society. All right reserved. Source


Bai J.-P.,State Energy Key Laboratory of Joint Exploitation of Coal and Coal bed Methane | Bai J.-P.,Shanxi Lanyan CBM Group Co. | Zhang D.-K.,State Energy Key Laboratory of Joint Exploitation of Coal and Coal bed Methane | Zhang D.-K.,Shanxi Lanyan CBM Group Co. | And 2 more authors.
Meitan Xuebao/Journal of the China Coal Society | Year: 2014

To study the internal thermodynamic characteristics of CH4 desorption in the production process and the mechanism of water vapor in the process of drainage decompression and gas recovery, a series of methane adsorption-desorption isotherm experiments on anthracite in coal seam 3 at Sihe Coal Mine were conducted at 20, 25, 30, 35 and 40℃ respectively. Based on Clausius-Clapeyron equation, the isosteric heat of adsorption and maximum heat of adsorption were calculated. These calculations indicate that the maximum heat of adsorption in process of elevated pressure (adsorption) and lowered stresss (desorption) is 23.31 kJ/mol and 24.02 kJ/mol. Therefore, it belongs to physical adsorption. However, the latter is greater than the former. From the point of view of thermodynamics, in the adsorption-desorption equilibrium system, dropping pressure alone does not lead to desorption while it causes liquid water to form local low pressure in the coal pores and water molecules vaporizes. The adsorption heat produced by water vapor molecules adsorbing on the coal pore surface is approximately 40 kJ/mol, which is far greater than the adsorption heat of methane, thus the methane on the surface of coal pores will be easily replaced by water vapor, and the desorption of methane eventually occurs. Source

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