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Research On AVO Forward Modeling Based On Rockphysics

Posted on:2008-09-22Degree:MasterType:Thesis
Country:ChinaCandidate:Y H ZhangFull Text:PDF
GTID:2120360218963734Subject:Earth Exploration and Information Technology
Abstract/Summary:PDF Full Text Request
Shear wave velocity is a parameter that geophysicists always want to obtain and is essential in AVO forward modelling. But at present there is no effective method to calculate shear velocity. For this, the method of calculating shear velocity based on rockphysics is developed. Firstly, using the relation between wave velocity and the moduli of rock constituents, rockphysics model is bulit. Then, the bulk and shear moduli of minerals are inversed by simulated annealing algorithm to calculate shear velocity. Model test and practical application both show that the algorithm is converging and the inversion result is reliable.Based on the calculated shear velocity, exact reflection coefficients are calculated and AVO forward modelling is carried out by using integrated Zoeppritz'equations. And the effects of various factors on AVO are analyzed through some typical models, especially the rockphysics parameters, such as porosity, shale friction and water saturation. Above achievements offer some basic data to predict the properties of rock and fluid, which can efficiently reduce the uncertainty and ambiguity of seismic interpretation.With consideration of generalized planar wave, the Zeoppritz'equations in viscoelastic medium is deduced by using the boundary conditions of stress continuity and displacement continuity. Then four kinds of gas-sands are designed to develop AVO forward modelling. And the differences between elastic and viscoelastic cases are analyzed. In addition, the effect of anisotropy is discussed using simplified anisotropic reflection coefficient equations. In this paper, some typical models are employeed to show that the algorithm is correct and feasible.Practical application in certain areas shows that S-wave velocity estimation based on rockphysics improves the accuracy of AVO forward modelling, and the analysis of rockphysics parameters effect on AVO can reduce the uncertainty of fluid prediction. The approved conclusion is valuable.
Keywords/Search Tags:Rockphysics, Shear velocity, AVO, Viscoelasticity, Anisotropy
PDF Full Text Request
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