Research Of Seismic Response In Fluid-filled EDA Media

Different fractured media has different seismic response which is just a representation in the fields of vision. How to catch the essence of fractured media with the representation is always an importance work of geophysicists, which is also the emphases of our research.A needed analysis is done to Hudson theory and Thomsen theory, and then a numerical simulation of P- and S-wave velocity of EDA media is also done. As a result, we bring forward a geometrical-mean method to calculate the velocities in this paper. On this basis, the analysis has two aspects: one is to analysize the essential relationship between pore-fluid and seismic response, and the other is the relationship between fracture orientation, crack density and seismic response.The former is mainly to find out the most sensitive seismic properties and identify the fluid anomalies. We analyze the sensitivity of some attributes to pore-fluid on macro- and seismic-scale through numerical simulation, and show the power of identification of the attributes, also the limitations given.The latter has two schemes on the basis of transformation of the equation of azimuthal P-wave reflection coefficient in EDA media. One is, in view of multi-azimuthal data, to give the numerical expression of fracture orientation directly using seismic applitude. With solving out the fracture orientation, we can analyze the relationship between the residual terms and the crack density, so the approximately linear equation between 1/A and crack density. The other is, from the point of AVO, to give the numerical expression of fracture orientation using the gradient on the basis of new idea of macroscopical fracture term C and microcosmic fracture term D, and the approximately linear equation between C and crack density.We put forward a new method to identify the pore-fluid and its type directly using seismic applitude given multi-azimuth data, which finds that the distribution of numerical value on the plot of normalized applitude varying with different incidence and azimuth of target zone can ascertain the fluid type. Moreover, a new crossplot C-D is also used to identify pore-fluid, which is not affected by azimuth and can disjoin the three types of pore-fluid easier than traditional P-G crossplot.The research in the paper, especially the experiment of numerical simulation in this domain provides wider vision and new methods for the identification of pore-fluid using seismic data, the determination of fracture properties and oil field exploration and exploitation.