LAYER-BY-LAYER RECURSION INVERSION OF INTERVAL VELOCITY FROM VSP DATA
ZHOU Jun1, XIE Chun-hui2, YANG Peng3
1. School of Energy Resources, Chengdu University of Technology, Chengdu 610059, China;
2. Northwest Branch Institute, China Academy of Petroleum Exploration and Development, Lanzhou 730020, China;
3. No. 6 Oil Recovery Factory, PetroChina Changqing Oilfield, Yulin 718606, China
Abstract:This paper reports a method for inversing interval velocity layer by layer according to VSP data, whose main feature is that the path of spread rays will be divided into linear transmission and refraction transmission, and then the interval velocity is inversed from top to bottom with VSP data. 5 layers level medium model is designed on the basis of matlab, and then the ray tracing method is used to synthesize VSP records for three kinds of well-source distance (300 m, 1500 m, 3000 m). A comparison of the inversion results of the two methods with model data shows that the linear method is applicable to the small well-source distance, and refraction method is applicable to all kinds of well-source distance. In addition, the running time of the refraction method is longer than that of the linear method, but the refraction method could only be weakly influenced by the error of first arrive, and its capability against interference is strong.
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