Prestack Elastic Impedance Inversion Theory And Its Application

As poststack acoustic impedance inversion use the seismic data of full angle multiple stack, so it weakens the reflection sensitivity of reservoir character in some kind of degree; and poststack inversion only can provide very few parameters such as P-wave impedance, which restrict the research on the aspect of lithology and fluid. Aim at the insufficiency of poststack inversion, this paper studies the theory of prestack elastic impedance inversion that use the prestack angle gathers of different incident angles, and has conducted the applied research of this theory on different kinds of real seismic data.First, based on the elementary theory of longitudinal wave’s AVO response, this paper deeply analysized the relationship between elastic impedance and P-wave velocity, S-wave velocity, density and incident angle. Then in view of the shortcoming of the different angles elastic impedance change much along with the angle in the value, has processed normalization study on the elastic impedance formula, and gave elastic impedance inversion arithmetic using the normalized formula based on the basic flow and theory of poststack impedance inversion. In order to obtain more lithology information, this paper has studied prestack elastic parameters and made processing for the normalized elastic impedance formula, used the direct parameter regression technology and gave the quantitative extraction method of the P-wave velocity, the S-wave velocity and the density from the inversion data, then abundant lithological properties such as the ratio of P-wave and S-wave velocity, poisson’s ratio and elastic modulus and so on can be obtained indirectly. Therefore, this method provided a new tool for the lithological and fluid study of underground reservoir. Using above study results, this paper has mainly carried on application research on the delta, the rivers and the complex delta - rivers - littoral facies reservoir, and then carried on description and forecast to the real reservoir according to the obtained data.From the research on the prestack elastic impedance inversion theory and application on real project, it has shown that the elastic impedance inversion realized the quantitative extraction of many kinds of lothological parameters, which provide rich information of the reservoir identification and forecast.