Application of gradient structure tensor method in CBM fracture identification and sweet spot prediction
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ORIGINAL PAPER
Application of gradient structure tensor method in CBM fracture identification and sweet spot prediction Chengqiang Zhao 1 & Yubang Zhou 2,3 & Yong Li 2,4 & Ping Zhao 3 & Lingling Huang 5 Received: 23 April 2019 / Accepted: 5 September 2019 # Saudi Society for Geosciences 2019
Abstract In view of the technical difficulties of the fine identification of micro-fractures and the prediction of sweet spot in coalbed methane (CBM) reservoirs in unconventional oil and gas reservoir exploration, this paper carries out the extraction and comparison of fractures on the basis of the gradient structure tensor (GST) method, combining with the real geological conditions of the Yanchuannan (YCN) work area. Based on the above, the Euler curvature at different angles is further extracted. Meanwhile, according to the data of five gas production wells in this work area, fracture networks at the top of the M2 target layer are displayed in 3D space. The frequency responses of the fracture networks are characterized by threshold filter histogram and fracture stress rose diagrams are also analyzed. The results show that the NE-trending micro-fractures are well developed and the interlaced fracture networks are dense in the study area, which is an ideal sweet spot for CBM. Therefore, this study verifies the efficiency and practicability of the GST detection method, and provides an innovative way for identifying CBM fracture networks and predicting sweet spot. Key words CBM . GST method . Euler curvature . Fracture identification
Introduction As the rapid development of unconventional hydrocarbon reservoir exploration, how to finely detect and identify the fractures in the heterogeneous hydrocarbon reservoirs such as CBM has become the key problem. At the same time, the
Responsible Editor: Santanu Banerjee * Yubang Zhou [email protected] 1
College of Nuclear Technology and Automation Engineering, Chengdu University of Technology, Chengdu, People’s Republic of China
2
College of Geophysics, Chengdu University of Technology, Chengdu, People’s Republic of China
3
Qinghai Prospecting Institute of Coal Geology, China National Administration of Coal Geology, Beijing, People’s Republic of China
4
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, People’s Republic of China
5
College of Foreign Languages & Cultures, Chengdu University of Technology, Chengdu, People’s Republic of China
accurate evaluation of the development of fractures is one of the main factors of the fine characterization and prediction of CBM and others. Seismic attributes, like coherence and curvature, have played a crucial role in the interpretation and processing of data in conventional energy exploration. Therefore, this study will proceed from seismic attributes, combining with the strong heterogeneity of unconventional reservoirs such as CBM and the constraint of real gas production wells in the study area, and carry out an initial study on innovative application. Additionally,
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