1. 1.中国石油化工股份有限公司石油物探技术研究院,江苏 南京 211103
2.华润（南京）市政设计有限公司,江苏 南京 210000
• 收稿日期:2015-03-02 修回日期:2015-07-30 出版日期:2015-09-20

### A New Ray Tracing Method for VTI Medium Based on Separated P-SV Waves

Kai Guo 1( ), Pengyan Wang 1, Tingting Lou 2

1. 1 Sinopec Geophysical Research Institute, Nanjing 211103, China
2 China resource(Nanjing) Municipal Design Co.Ltd, Nanjing 210000, China
• Received:2015-03-02 Revised:2015-07-30 Online:2015-09-20 Published:2015-09-20

In recent years, modeling and imaging techniques for VTI medium have developed rapidly. Ray tracing in VTI medium is the key issue, whose precision and stability directly affect the results of modeling and imaging. Ray tracing in VTI medium is usually based on the eikonal equation and ray equation derived from the dispersion relation of Alkhalifah (2000). The assumption is that the P wave and S wave are independence, and the velocity of S wave is zero. Thus, in some particular cases, this method is lack of accuracy and stability. In this paper, a new ray tracing method was proposed to overcome this problem. We separated P-SV waves to get the phase velocity of the qP wave, and then to get the eikonal equation and ray equation of qP wave, through which the precision and stability were improved. At the end, numerical tests were made to prove the effectiveness of this method.

Fig.1 Traveltime contours using new ray equation

Fig.2 The curves of phase velocity for isotropic medium Black expresses the exact phase velocity curve;Red expresses the phase velocity curve when VSO=0;Green expresses the phase velocity curve of separated P-SV waves

Fig.3 The curve of phase velocity for Mesa clay Shale VTI medium Black expresses the exact phase velocity curve;Red expresses the phase velocity curve when VSO=0;Green expresses the phase velocity curve of separated P-SV waves

Fig.4 The curve of phase velocity for Taylor Sand VTI medium Black expresses the exact phase velocity curve,red expresses the phase velocity curve when VS0=0,green expresses the phase velocity curve of separated P=SV waves

Fig.5 Analysis on VTI medium velocity isoline in constant gradient model and composite （a）Travel time isoline of Alkhalifah ray function;（b）travel time isoline of new ray function;（c）composite of two functions

Fig.6 Analysis on VTI medium velocity isoline in constant gradient model and composite （a）Travel time isoline of Alkhalifah ray function;（b）Travel time isoline of new ray function;（c）Composite of two functions
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