Fracture detection with three dual-scanning shear-wave splitting methods
Zhang Jianli1,2, Wang Yun3, Liu Zhibin1, Li Xuxuan1
1. CNOOC Research Institute, Beijing 100027, China;
2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;
3. School of Geophysics and Information Technology, China University of Geosciences(Beijing), Beijing 100083, China
Abstract：Shear-wave splitting (SWS) plays a key role in fracture detection.Recently,the splitting inversion methods of dual-scanning type,which have been merely used in deep geophysical prospecting,now are used in converted wave for oil and gas reservoir detection.In this paper,we firstly summarize the processing flow of dual-scanning methods,then test the performance of three dual-scanning (transverse energy,rotation correlation,and covariance matrix) with different azimuths and different offsets in a fracture model.Finally we apply these three methods to a tight sandstone gas reservoir exploration in West China,and compare inversion parameters with those calculated by energy ratio method.Based on our work,the following conclusions are obtained:1.All the three dual-scanning methods show a reliable performance when the radial direction keeps away from fracture azimuth; 2.The transverse energy method is the most reliable method among these three,which can work well even the radial direction closes to fracture azimuth; 3.The inversion precision of dual-scanning methods can be affected by offsets.
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