The Two-phase Media AVA Forward Analysis And Reservoir Parameter Sensitivity Analysis

Reservoir geophysics theory has played an important role in the current oil andgas prediction.It can be applied to study the physical properties of reservoir, spatialdistribution, fluid distribution law by making use of seismic technolgy,theexperimental theory of rock-physics, and other methods.It also helps us to descriptand evaluate reservoir qualitatively or quantitatively. A large number of rock physicsresearch results have confirmed that the use of two-phase medium model as areservoir medium model assumptions will be more in line with the objective law ofthe reservoir, is expected to improve the accuracy of reservoir prediction, fluididentification. Multi-wave prestack inversion is based on the multi-wave amplitudeinformation and has provided intuitive lithology parameters for the reservoirprediction. On the basis of the amplitude characteristic equation of two-phaseisotropic medium this thesis analyzes AVA features which are produced by fourgas-bearing sandstone interface and analyzes the factors that affect stack AVAinversion accuracy, the parameter sensitivity analysis. The research of this thesis ismainly divided into the following aspects:1) After refer to many related documents which studies AVA technology, thisthesis has compiled the exact formula of the amplitude characteristic equation in thefour kinds of two-phase medium interface case. Having built a conversion relationshipbetween the conventional lithology parameters (such as P-wave velocity, shearvelocity, density, porosity and fluid properties) and the formula of the elasticparameters in the theory of two-phase medium, so that the practical application of thetwo-phase media model become possible. 2) Author wrote a program,designed a theory two-phase media model, forwardthe AVA characteristic curve of the top and bottom reservoir interface which comparedwith amplitude characteristics of the single-phase isotropic medium under theconditions of equation (Zoeppritz equation).It can be found the difference on bothcharacteristics. Through forward analysis, the results show that distribution of theseismic waves energy at the interface is obviously different from in the single-phasemedium, for the presence of fluid and slow longitudinal wave.3) Two-phase media theory forward modeling of the AVA characteristic curvesof minimal porosity of tight sandstone interface. Verified the correctness of theforward algorithm for two-phase media AVA,which AVA characteristics curve bycomparing the single-phase isotropic medium. It also explains the single-phasemedium is just the special circumstances of two-phase medium.4) Based on two-phase media with amplitude characteristic equation, four kindsof water-bearing and gas-bearing sandstone interface of the AVA curve have beenforwarded and their characteristics have been analyzed.5) Fixed lithology parameters, only changing a parameter of the forward testmethod to analyze the sensitivity of the various lithological parameters and reservoirparameters on the characteristics of AVA. It can scientifically help optimizinginversion parameters and designing reasonable inversion. Testing the sensitivity ofparameters, AVA occupies a very important position in the back as a whole.