Influential Factors and Forecast of Microcrack Development Degree of Longmaxi Formation Shales in Nanchuan Region,Chongqing
Received date: 2015-04-20
Revised date: 2015-05-22
Online published: 2015-08-10
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,ROvalue,porosity and tectonic deformation,and so on.The relation between both of the indexes “>100nm 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 100nm 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 100μm 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.
Key words： Shale; Microcrack; Influential factor; Development degree; BP Neural Network(BPNN)
WANG Ji-lin，ZHU Yan-ming，GONG Yun-peng，FANG Hui-huang . Influential Factors and Forecast of Microcrack Development Degree of Longmaxi Formation Shales in Nanchuan Region,Chongqing[J]. Natural Gas Geoscience, 2015 , 26(8) : 1579 -1586 . DOI: 10.11764/j.issn.1672-1926.2015.08.1579
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