Multiphase Medium MultiWaves AVO Forward Modeling Comparison Research

This paper is supported by the program of National Natural Science Foundation of China(No.40474043), in which the technique of multiphase medium multi-waves AVO forward modeling issystemically compared and studied. On the basis of the comprehending and understanding of seismicwaves' propagation properties in models and their interface, the paper mainly studied the relationshipsof the velocities of constituent porous medium defined by Dr Niu and the velocities of P-wave andS-wave of Biot-Gassmann equations with the porosity and saturation of the medium, and therelationships of the reflection coefficient of the P-Waves and SV-waves with the porosity and saturationof the medium, which provide a referential theory basis for forward application of the multiphasemedium AVO technique. The correlative studied results can also be expanded to the field of the seismicexploration for the petroleum, gas, hydrates and water resources which are related to multiphasemedium.AVO technique analyzes the characteristic and regular of the amplitude of the pre-stack seismicwaves varied with the offset, from which the properties and lithology of the oil and gas reservoirs can bepredicted and judged. The former most AVO researches are based on single-phase solid medium,however the real gas and oil reservoirs are multiphase medium, that is the unification of multi-mediumcomponent of the gas, oil, water, and rock matrix. For improving the seismic exploration work, thispaper based on the former works systemically studied the multiphase medium P-P and P-SV wavesAVO forward modeling. Mainly include the several aspects below:First, this paper introduced the developing brief and main questions of the AVO technique andseismic waves propagation in multiphase medium and the interfaces.Secondly, this paper generally summarized the fundamental and basic techniques of the AVOtechniques. Especially I picked out several representative and common equations from AVOapproximate equations of the P-P and P-SV waves to compared with the precision solutions of theZoeppritz equations, from which high precision AVO approximate equations suitable to theory researchare acquired and provided for the next step of AVO forward modeling.And then the comprehensive comparisons and researches are carried out between the Niu1equations of constituent porous medium velocities models, quadratic interpolation speed Niu2 equationsand classical Biot-Gassmann equations.Finally, combined the former works and familiar reservoirs in the oil and gas hydrates to designmultiphase reservoirs medium models, I used the approximate AVO equations to calculate, plot andanalyze, including the AVO researches of the top and bottom of the aiming reservoir. At the same I alsoutilized the radial tracing method to simulate the CDP record at different angle, and combined with thereflection coefficient curve to comprehensive studied the several multi-component medium models.Generally, the AVO research of multiphase medium is concerned more factors than those of thesingle-phase solid medium,by rationally choosing and deducing the component base functions with theBiot-Gassmann equations we can acquire more accurate results, furthermore component mediumequations have more applicability and agility, which provide the theory basement of multiphase mediumAVO backward, fluid type prediction and lithology and properties prediction of the reservoirs.