The Study Of Seismic Inversion Method For Fracture Reservoir

This paper summarizes the anisotropic theory of crack reservoir. We get the equivalent elastic coefficients of crack media on the use of Hudson's model, and provide the method how to get wave propagation velocity and attenuation coefficient in the fractured media which has a horizon symmetry axis. We simulate the variation of phase velocity and attenuation coefficient while crack parameters change., and find that the attenuation coefficient is more reliable than wave velocity. So we do an actual application here.The data of the exploration area is a three-dimension data. We applied time-frequency analysis and frequency attenuation attribute to predict the distribution of reservoir physicality. During analysing the frequency spectrum attribute of well X-1 and well X-3 we found that the starting attenuate frequency and low-frequency energy dovetail well with the interpretation pore. We extracted this tow frequency properties from stack gather of this region, and obtained reservoir properties for the reservoir layers. By stacking the pre-stack gather in different azimuth, we got two azimuth gathers which have uniform coverage and high S/N Ratio. We detect the fracture development level using the difference of the frequency of 85% energy in the two azimuth gathers. Finally we provided the distribution planes of fracture presence in every reservoirs and cap rock.In this exploration area, there isn't S-velocity logging. But S-velocity log of the well is very important during some inversion works, such as impedance inversion and elastic impedance inversion. It can provide both low frequency model and high frequency model. We must use it during the extraction of angel wavelet too. Fluid replacement based on rock physics model of Gassmann equation can inversion the S-velocity using both logging data and the analysis of core sample. Logging data can provide reliable petrophysical parameters. Using the explanation of log datas and the inverted S-velocity to forward the AVO of the aim reservoir layer can provide some information about using reflection to detect fracture. We forwarded the AVO response and found that if only using wide-azimuth gather's large incident angel data can detect fracture effectively. But the data of this area can provide narrow azimuth only. So we don't use the AVO information of different azimuth to detect fracture. The data of this exploration has a high S/N Ratio. The max of incidence angel for the aim reservoir layers is 31 degree. It comes up to the conventional pre-stack elastic impedance inversion requirement. We extracted four angel gathers from the pre-stack data and did the elastic impedance inversion.