Wang J.-L.,Key Laboratory of CBM Resources and Reservoir Formation Process |
Wang J.-L.,China University of Mining and Technology |
Zhu Y.-M.,Key Laboratory of CBM Resources and Reservoir Formation Process |
Zhu Y.-M.,China University of Mining and Technology |
And 2 more authors.
Natural Gas Geoscience | Year: 2015
By field inspection, laboratory test and observation under microscope, the following characteristics of Longmaxi Formation shales in Nanchuan region, Chongqing were summed up: The scope of microcrack width, the dominant orientation of microcrack and the manifestation in the graph of the amount of mercury injected by stages in experiment. It was analyzed that the effects upon the microcrack development of shale were caused by mineral composition, TOC, RO value, porosity and tectonic deformation, and so on. The relation between both of the indexes “>100 nm pore volume”, “total amount of mercury injection” and microcrack development degree was studied. By using the experimental data such as mineral composition content, TOC, RO value and porosity, combined with the structure factor, quantitative indexes of the influential factors about microcrack development of shale were built. The quantitative relationship between the influential factors of microcrack and the degree of microcrack development was researched by using BP Neural Network (BPNN) model. The forecast for the degree of microcrack development was studied by using BPNN at the same time. It is concluded that the microcracks with width between 100 nm to 100μm are developed in Longmaxi Formation shales in the research area. These microcracks constitute a network in different ranks. The graph of the amount of mercury injected by stages indicate the development degree of ultra-microcrack of shale to a certain degree. The width of microcracks in micron-level focuses the range of under 100 μm and the microcrack in micron-level is related to tectonic deformation tightly. The weight matrix in BPNN model indicates the quantitative relationship between the influential factors of microcrack and the degree of microcrack development. Therefore, the degree of microcrack development can be forecasted quantitatively by using BPNN model. ©, 2015, Science Press. All right reserved.
Liu J.,China University of Mining and Technology |
Liu J.,Key Laboratory of CBM Resources and Reservoir Formation Process |
Jiang B.,China University of Mining and Technology |
Jiang B.,Key Laboratory of CBM Resources and Reservoir Formation Process |
And 8 more authors.
Arabian Journal of Geosciences | Year: 2015
Deformation characteristics and pore structure of coals from Xinjing coal mine have been studied, as well as the control mechanism of structural deformation on coal structure characteristics, based on observation in coal mine and deformation analysis of typical coal samples, combined with microscopic observation and mercury intrusion porosimetry (MIP). The research has revealed that coals of Xinjing coal mine mainly suffered from brittle deformation and consisted of primary and cataclastic structural coal, and a small part of intensively deformed coals develop locally in no. 3 coal seam. With the structural deformation enhanced, the coal strength becomes worse, the mortar textures and fracture density increase, and the scale and aperture of fractures increase at first and then decrease. The pores of coal, with high total pore volumes and porosity, are mainly composed of micropores and transitional pores, and the pore volumes of macro- and mesopores vary over a large range. The number of macropores greatly correlates with the density and aperture of joints and fractures, and the number of mesopores is determined by the enrichment of mortar textures. Three pore structures are proposed according to the shapes of intrusive mercury curves, of which the parallel type has good pore connectivity and improved permeability, the angular type has both good pore connectivity and permeability induced by the structural modification, and the double S type has poor porous connectivity which is unfavorable for coalbed methane exploitation and most possible for coal and gas outburst during mining. © 2014, Saudi Society for Geosciences.
Jiang W.,China University of Mining and Technology |
Jiang W.,Key Laboratory of CBM Resources and Reservoir Formation Process |
Wu C.F.,China University of Mining and Technology |
Wu C.F.,Key Laboratory of CBM Resources and Reservoir Formation Process |
And 4 more authors.
Energy Sources, Part A: Recovery, Utilization and Environmental Effects | Year: 2013
To the gas system of multi-coalbeds overlay in Zhina coalfield, the initial proposals about coalbed methane (CBM) exploitation, based on a large number of coalfield geological exploration data and the results obtained in coalbed methane exploration recently, was proposed through the analysis of coal reservoir's flexibility energy on horizontal and that of different gas systems on vertical, respectively. The study revealed that Zhongzhai exploration area is the independent gas system of multi-coalbeds overlay. The relation of methane flexibility energy and burial depth of a coalbed show intense fluctuations among the four gas systems, however, methane flexibility energy is increasing with burial depth of coalbed in every different gas system. Adopting subsection fracturing and drainage pattern, the first gas system was the best fit for CBM exploitation. Zhi-2 well, a unified gas system of multi-coalbeds overlay, is located in Zhuzang syncline, of which coal reservoir's flexibility energy is increasing with the burial depth. According to the coal seam spacing and flexibility energy, No. 16 and No. 23 coal seams should be exploited first between two sets and adopt the pattern of subsection hydraulic fracturing and multiple layer drainage. Copyright © Taylor & Francis Group, LLC.