Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process

Tongshan, China

Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process

Tongshan, China
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Zhang X.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | Zhang X.,China University of Mining and Technology | Wu C.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | Wu C.,China University of Mining and Technology | And 2 more authors.
Journal of Geophysics and Engineering | Year: 2017

The micropore structure of a tight sandstone is the decisive factor in determining its reserve and seepage characteristics. An accurate description of the pore structures and a complete characterization of the gas-water permeability are critical when exploring for tight sandstone gas. One simple and effective way to quantitatively characterize the heterogeneity and complexity of the pore structures in a low permeability reservoir is the fractal dimension. In this study, three different methods, each utilizing mercury intrusion porosimetry (MIP) data, were adopted to analyze the fractal dimensions and the fractal curves of sandstones from the no. 8 layer of the Xiashihezi Formation (He 8 member) in the Linxing block, dated from the Middle Permian. The morphological features of the fractal curves, the characteristics of the fractal dimensions and the theoretical differences between these three methods were also discussed. The results show that the fractal dimensions obtained by method I reflect the characteristics of the remaining pores that are not intruded by mercury, and they show that the involved pore scales are more comprehensive. While in methods II and III, both obtain the fractal dimensions of the pores intruded by mercury, the difference between them is in the selection of a simplified pore shape model, which results in the fractal dimensions differing by a value of 1 between them. No matter which method is adopted, the pore structures of tight sandstone reservoirs in the Linxing block exhibit fractal characteristics. However, the fractal dimensions obtained by method I are more suitable for describing the complexity and petrophysical properties of the tight sandstone pores in the He 8 member of the Linxing block. The fractal curves obtained by different methods are consistent to a certain extent in terms of morphological changes. Small pores (rmax-point) are the critical factor affecting the seepage characteristics of the reservoir. © 2016 Sinopec Geophysical Research Institute.


Yu S.,China University of Mining and Technology | Yu S.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | Bo J.,China University of Mining and Technology | Bo J.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | And 2 more authors.
Energy and Fuels | Year: 2017

Coupled with isothermal adsorption and the Steele potential function, the characteristics of nanopores and their impact on methane adsorption and diffusion in low- to medium-rank tectonically deformed coals (TDCs) were revealed by high-pressure mercury intrusion and low-pressure N2/CO2 gas adsorption. The specific surface area (SSA) of low to medium TDCs is mainly provided by micropores (<2 nm, 96.64-99.56%), and the pore volume is mainly provided by macropores (>50 nm, 99.68-99.91%). The fractal characteristics of nanopores can be divided into four groups, i.e., D1 (>100 nm), D2 (<100 nm), D3 (>8 nm), and D4 (<8 nm). For primary coals and brittle deformed coals, D1 > D2, indicating that the heterogeneity of seepage pores is stronger than that of adsorption pores. For scaly coals, D2 ≈ D1, demonstrating the close heterogeneity and connectivity in adsorption and seepage pores, which are beneficial for coalbed methane (CBM) desorption and diffusion. However, D2 > D1 for wrinkle and mylonitic coals, indicating a stronger heterogeneity in adsorption pores than seepage pores, especially for mylonitic coals. D4 gradually increases with the enhancement of tectonic deformation, and D3 shows a sharp increase in wrinkle coals. D2, D4, and SSA (<8 nm) all have a better positive correlation with the maximum adsorption capacity (R2 = 0.57, 0.54, and 0.76, respectively), indicating that pores <8 nm in size have a dominant role in the adsorption capacity. With abundant activated desorption pores (0.7-1.5 nm), the content of schistose coals is between the contents of configuration diffusion pores (0.5-0.7 nm) and Knudsen diffusion pores (>1.5 nm). Schistose coals are good CBM reservoirs, followed by the scaly coals. Lacking activated desorption pores and Knudsen diffusion pores, wrinkle and mylonitic coals have a high incidence of coal and gas outburst. © 2017 American Chemical Society.


Li T.,China University of Mining and Technology | Li T.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | Wu C.,China University of Mining and Technology | Wu C.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | And 2 more authors.
Journal of Natural Gas Science and Engineering | Year: 2015

Micro-fractures and macro-fractures are abundant in coal reservoirs, and the formation of such fractures depends on the coal-bearing environment. In addition to the development of fractures, the gas content and coalbed methane productivity are also controlled by the coal-bearing environment. Research on micro-fracture characteristics is conducted through microscopic observation, and research on macro-fracture characteristics is conducted by investigating coal cores. The method of quantitative statistics is adopted for the measure of the submaceral, and the coal facies parameters are calculated. The coal structure is explained using logging data. Then, the coalbed methane productivity controlled by the coal facies is examined. The results show that Type D micro-fractures are well developed, followed by Type C micro-fractures. The micro-fractures are primarily tensional fractures, implying that the formation of micro-fractures is controlled by external stress. Micro-fractures pass through the macropores and effectively link with other micro-fractures, whereas macro-fractures are primarily developed in clarain bands and cataclastic texture coal. The gas content increases with the gelatification index (GI) and ratio of vitrinite to intertinite (V/I) in the coal reservoir, which are favourable coal facies geological conditions for coalbed methane production. However, whereas the production of the coalbed methane wells is in its initial stage, the methane produced is mostly free and strongly desorbed gas. The coal structure primarily contributes to the permeability of the coal reservoir. The development of Type II coal can increase the production of methane, whereas the development of Type III coal has the opposite effect. © 2015 .


Li L.,China University of Mining and Technology | Wei C.,China University of Mining and Technology | Wei C.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | Qi Y.,China University of Mining and Technology | And 6 more authors.
Arabian Journal of Geosciences | Year: 2014

Coalbed methane (CBM) commercial developments have made breakthroughs in a few areas in China, including Qinshui Basin and Ordos Basin. For years, Eastern Yunnan Province and Western Guizhou Province have been the new hot spots of CBM study in China. Predecessors have discussed CBM reservoir characteristics, CBM system, and geological process evolution. Basing on previous research, we studied the formation history of the CBM reservoir by numerical simulation at the Shuigonghe Syncline in Western Guizhou. Data were obtained from geological survey and laboratory testing. According to the simulation results, the CBM reservoir formation history can be divided into five stages. In addition, a plane distributive contour map of CBM reservoir formation-related data was constructed to recognize the change in CBM content and CBM dissipation quality at different stages in the region. Each stage has its feature on CBM generation, dissipation, and accumulation speed. Geological process controlling factors, including burial history, tectonic history, geothermal history, and maturation, were analyzed. All factors acted together and formed the CBM reservoir in the Shuigonghe Syncline. Among these factors, tectonic evolution history is the most important because it determines the whole generation-preservation-dissipation process of CBM. The other factors affect the process in various ways. © 2014 Saudi Society for Geosciences.


Li W.,China University of Mining and Technology | Li W.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | Li W.,University of Queensland | Zhu Y.,China University of Mining and Technology | Zhu Y.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process
Energy and Fuels | Year: 2014

Vitrinite samples inserted into a furnace at room temperature and heated at a rate of 10 °C/h were subjected to X-ray diffraction analysis, Fourier transform infrared spectroscopy (FTIR), and solid-state 13C nuclear magnetic resonance spectroscopy (13C NMR) to characterize the macromolecular structure of vitrinite of different ranks of coal, which was discussed with respect to changes in its chemical structure. The results demonstrate that the relationship between average reflectance of the vitrinite and temperature is linear. The structural parameters of vitrinite separated from the coking coal sample collected from the Lujiatuo mine (LJTV) (d002 = 3.56 Å, Lc = 11.62 Å, La = 10.99 Å) were obtained. The FTIR spectra include bands characteristic of aliphatic C-H stretching, with the ratio of aliphatic oxygen-containing compounds decreasing with increasing rank of the vitrinite samples. The C=O stretching contribution is lower than the aliphatic C-H stretching contribution, whereas the aromatic carbon contribution is high in all of the samples. The vitrinite structural parameters, e.g., the A factor, C factor, CH2/CH3, A ar/Aal, Al/OX, Al/C=C, and C=O/C=C, were calculated. The intensity of the aromatic carbon peak is considerably greater than that of the aliphatic carbon peak. The 13C NMR spectra reveal that the aliphatic carbon content decreases progressively with increasing thermal maturity for the replacement of aromatic hydrogens by condensation. The CCH3 groups are removed more slowly than are the C(CH2)C groups. The coalification progress was divided into two stages based on the CH 2/CH3 ratio, which first decreases and later increases. As revealed by the structural parameter fa, the aromaticity of vitrinite increases during pyrolysis. © 2014 American Chemical Society.


Li X.,China University of Mining and Technology | Li X.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | Fu X.,China University of Mining and Technology | Fu X.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | And 2 more authors.
Hydrogeology Journal | Year: 2016

Exploitation of coalbed methane (CBM) involves groundwater extraction to depressurize coal reservoirs. This can involve groundwater extraction from multiple coal seams (commingled drainage). Interlayer interferences, caused by heterogeneity of hydrodynamic fields of the different coal gas reservoirs, can restrain CBM production. Understanding of the hydrogeological characteristics of each reservoir, inseparable from characteristics of the sequence stratigraphic framework, is critical for CBM exploration. Analysis of Zhuzang syncline in Guizhou province, China, found gas- and water-blocking strata near the maximum flooding surface in the upper part of each third-order stratigraphic sequence; thus, the hydrogeological units were divided vertically (SQ4, SQ3, SQ2 and SQ1) by the boundaries of the third-order sequence. The commingled-drainage CBM wells were analyzed by numerical simulation and Extenics theory, on the basis of characteristics of the hydrogeological units. Gas content, reservoir pressure and hydrodynamic parameters were found to vary between the hydrogeological units. The interlayer interference was not obvious where there was commingled drainage within single hydrogeological units with similar hydrodynamic force; this was validated by observing the consistent pressure decrease within each reservoir using historical matching. Since the source of drainage water varied from stratum SQ3 to SQ4 (containing lower hydrodynamic force compared to SQ3), it was obvious that groundwater extraction from SQ4 was restrained by SQ3, by showing obvious interlayer interference and restrained CBM production during commingled drainage across the different hydrogeological units. Reservoirs within each single hydrogeological unit tend to obtain higher CBM yield, thus take priority for commingled drainage. © 2016 Springer-Verlag Berlin Heidelberg


Zou M.,China University of Mining and Technology | Zou M.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | Wei C.,China University of Mining and Technology | Wei C.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | And 3 more authors.
Energy Exploration and Exploitation | Year: 2013

Based on the geological data and drainage parameters of QN01 coalbed methane (CBM) well which is located at the southern Qinshui Basin, by using CBM reservoir numerical modeling technology, 15 years' gas recoverability is predicted and the dynamic variation of reservoir pressure is studied for both QN01 well and an assumed 300 x 300m well net group by using the same parameters as QN01 well. The results show that for single well, within the first 300 days, gas recoverability is similar everywhere in the gas supply area and the dropping rates of reservoir pressure are all below 1 KPa/d. Further more, the region more than 120 m away from the well bore hole is not beneficial for gas recoverability. For well net group, dropping rates of reservoir pressure are higher than 1 KPa/d. With the increase of the distance to the well bore hole, gas outcomes more and more in the gas supply area. Similarly, the "secondary reservoir pressure dropping" caused by the well interference in the well net group has a positive correlation with the distance to the well bore hole, and the dropping rates of reservoir pressure of the well net group are approximately twice as large as those of the single well. © 2008 IOS Press and the authors. All rights reserved.


Li W.,China University of Mining and Technology | Li W.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | Li W.,University of Queensland | Zhu Y.,China University of Mining and Technology | And 4 more authors.
Energy and Fuels | Year: 2014

An energy barrier mechanism exists in the hydrocarbon generation of vitrinite. Traditional coal geochemistry is unable to explain the mechanism of the macromolecular structure evolution in the process of hydrocarbon generation. This paper studies the hydrocarbon generation characteristics by thermal simulation experiments to obtain the control mechanism of the vitrinite macromolecular structure evolution control on hydrocarbon generation. The vitrinite structure characteristics were studied by Fourier transform infrared spectroscopy (FTIR) and carbon-13 nuclear magnetic resonance (13C NMR), and the structural parameters of vitrinite were calculated. On the basis of building the model of the macromolecular structure in a vitrinte sample, the coupling mechanism between hydrocarbon generation and the evolution of the vitrinite structure was determined through quantum chemistry. These results are important and practical for the coalification theory and coalbed methane (CBM), shale gas, and other unconventional gases. The results showed that the hydrocarbon production rate increased along with increasing maturity. Gaseous hydrocarbon consists of methane and heavy hydrocarbon alkanes and alkenes. The C2-5/C1-5 ratio decreases linearly with increasing maturity. The intensity of the vitrinite functional group absorption peak decreases. Aliphatic hydrocarbons have an absorption peak before 430 C, which then declines to periodic variation characteristics. The intensity of the absorption peak because of the Cî - O moiety of aromatic hydrocarbons (1600 cm-1) decreases. The response of the intensity of substituted aromatic hydrocarbons is weak. A polyester reaction occurs at 450 C. The aromatic carbon rate change is divided into three stages. The average molecular potential energy decreases with the pyrolysis process. Vitrinite removed the methyl macromolecular structure first and then the aliphatic hydrocarbons, aliphatic chain rings, and other bonds. © 2013 American Chemical Society.


Zou M.,China University of Mining and Technology | Zou M.,Key Laboratory of Coalbed methane Resource and Reservoir formation Process | Wei C.,China University of Mining and Technology | Wei C.,Key Laboratory of Coalbed methane Resource and Reservoir formation Process | And 5 more authors.
Arabian Journal of Geosciences | Year: 2014

Drainage of formation water controls pressure dropping behavior of coalbed methane wells. Different behaviors indicate that formation water can be classified into two types. The first type is ineffective water, representing the water from aquifers of strong, extremely strong water yield property, or phreatic water. It is difficult to generate pressure dropping when this type of water is pumped. The other type is effective water, representing the water from aquifers of middle or weak water yield property. Pressure decline will occur if this type of water is pumped. Based on the modified Duipt equation, the production of effective water and the production percentage of ineffective water for well QNPN01 are calculated considering the variations of influence radius, absolute permeability, and relative water permeability. The results show that in the single water flow stage, the production of effective water and the production percentage of ineffective water drop in the zigzag way at first and then keep stable roughly. In the water-gas flow stage, the production of effective water decreases firstly and then keeps stable, while the production percentage of ineffective water increases firstly and then keeps stable. Furthermore, the production of effective water in unit pressure decline indicates that the process of pressure dropping can be divided into four stages. The first one is a single water flow stage in which pressure dropping completely depends on effective water. The second one refers to the beginning of a water-gas flow stage. In the stage, pressure dropping strongly depends on effective water. Pressure dropping caused by effective water drainage starts to be replaced by gas desorbing in the third stage, and completely replaced in the fourth stage. © 2013 Saudi Society for Geosciences.


Wang H.,China University of Mining and Technology | Wang H.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | Fu X.,China University of Mining and Technology | Fu X.,Key Laboratory of Coalbed Methane Resource and Reservoir Formation Process | And 6 more authors.
Journal of Natural Gas Science and Engineering | Year: 2015

Previous studies on N2-ECBM (N2-enhanced coalbed methane) have focused on experimental investigation or numerical simulation of coalbed methane recovery processes using pure N2 or binary gas (CO2/N2) injection. Experimental studies on the changes in pore structure and permeability during N2 injection have been limited. In this study, N2 injection experiments, mercury intrusion porosimetry and permeability measurements were conducted to investigate the changes in pore structure and permeability caused by N2 injection of semi-anthracite coal from the Lu'an mining area in the Qinshui basin, Shanxi Province, China. The results show that the total pore volume markedly increases during N2 injection, with increases in transition pores, mesopores and macropores of 8.0%, 50.0% and 138.3%, respectively. Nitrogen injection improves the pore size distribution: the incremental pore volume variances of transition pores, mesopores and macropores after treatment are 2.1%, 47.8% and 141.0%, respectively. Porosity and permeability markedly rise during N2 injection, by 22.6% and 29.9%, respectively. These results demonstrate that N2 injection mainly affects macropores, followed by mesopores and transition pores, and reformation of the micropores is limited. Nitrogen injection alters the pore structure of coal, which leads to an increase in the pore volume and improvement of the pore size distribution and connectivity: these changes facilitate the diffusion and transfusion of coalbed methane. The permeability of the coal sample was improved as a result of N2 injection, indicating that N2 injection could be used to enhance the permeability of CBM reservoirs. These findings will lead to a better understanding of the interactions between pores and N2 during N2 injection and hence can be applied to improve CBM recovery for non-productive or low-productivity CBM wells. © 2015.

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