Based On Gassmann Equation Elastic Parameters Numerical Simulation

With the deepening of oil and gas exploration and development, oil and gas reservoirs become more complex, the exploration focus transfer from the structural reservoir to lithology reservoirs and subtle reservoirs. On the one hand, the exploration targets gradually becomes deeper, smaller and complex, more difficult exploration, the prediction accuracy requirements are also increasing. On the other hand, the ultimate goal of reservoir prediction in addition to determine the existence of the reservoir, forecast level of reservoir development is good or bad, also need to determine the quantitative nature of the fluid contained in reservoir, fluid reservoir characteristics of the wave field. The quantitative determination mainly rely on seismic rock physics to set up the "bridge" between the relationship of seismic data (properties parameter) and oil reservoir characteristics (elastic parameters). Seismic rock Physics main use the intrinsic relations that the nature of reservoir rock and its pore fluid versus the seismic property parameter.Based on the systematic theory and media models of rock physics property such as elastic, viscoelasticity and anisotropy in rocks, the empirical relations between seismic attribute versus reservior property parameter are established. By uses of the techniques such as fliud substitution and so on, the reference fundamentals on lithologic reservoirs and subtle reservoir exploration. The core of fluid substitution is the Gassmann effective medium theory, Based on this, using Gassmann equation numerical simulation of elastic parameters is meaningful.After determining this Gassmann effective medium is the theory of the core content, describes some applications of rock physics basis,such as the assumptions and application conditions of Hashin-Shtrikman bounds, V-R-H average model,Wood fluid modulus formula, K-T theory, Effective Self-Consistent Theory and The Differential Effective Medium theory model, the geometry description to different shape inclusion, and the mathematic expression. And some of the classic formula for a summary of equivalent experience.A comprehensive exposition the theory assumptions of the Gassmann equation of fluid substitution,simplify derived the fluid substitution equation, gives Gassmann equation commonly used the mathematical expression form; summary description the effctive parameter selection methods of fluid substitution, summary based on the Gassmann equation 3 sets of detailed process of fluid substitution, giving some substitution examples. According to different lithology rocks, using Gassmann equation different forms of fluid substitution,to quantitative analysis. Through quantitative analysis found that the reverse phenomenon of the porosity substitution and fluid substitution, which inconsistencies with the actual laboratory tests, then giving the detail graphic quantitative analysis of the phenomenon, found that the density difference is too large causes leading to reverse. Therefore emphasizes on the importance of fluid substitution forword modeling, the actual value of fluid substitutions only under certain physical meaning.In the real data applications, Because based on single-well information seismic response of reservoir simulation and fluid identification are more based on deconvolution model, However,the kinetic characteristics of the wave field of deconvolution simulation results was not obvious for the complexity model of the geological. For this problems,proposed base on Gassmann equation fluid substitution wave equation simulation technology, from the point of wave equation to describe the seismic response of complexity reservoir model with different fluid states and different porosity, analyzed under different substitution of the wave field characteristics, prediction from the known to unknown. Also on the purpose of the reservoir log data (100% saturated water, 20% saturated gas, 40% saturated gas, 60% saturated gas, 80% saturated gas, 100% saturated gas)fluid substitution, (0.00,0.02,0.05,0.08,0.12,0.16) proposity substitution, for the use seismic data conduct gas - water identification to provide rock physical foundation.