Study On High-resolution Velocity Analysis In VTI Medium

Because of the generally existence of seismic anisotropy in earth’s crustsedimentary strata, especially the transversely isotropic with a vertical symmetryaxis (VTI) media, study on seismic anisotropy is irreplaceable in order to increasethe precision of seismic data processing and interpretation. It is of great importancein the expanding of exploration target, time-depth conversion processing, velocityanalysis and NMO in long offset acquisition. Velocity analysis is a key step inseismic data processes and interpretation. Traditional velocity analysis technologiesare based on the assumption of an isotropic media, and are common applied inproduction. In practice, the results of traditional velocity analysis methods based onassumption of isotropic can not meet people’s increasing requirement on theprecision when anisotropy exists in sedimentary strata. Development of velocityanalysis in anisotropic media is important to the evolution of seismic dataprocessing and interpretation in deep earth.In this paper, firstly we review the theory of the seismic anisotropy, such as thecauses and classification of anisotropy, anisotropic parameters, phase velocity andgroup velocity of anisotropic media. Taking the VTI (transversely isotropic with avertical symmetry axis) media which is common exist in sedimentary rocks as themain object of study, we briefly introduce anisotropic normal moveout velocityequation and one-step, two-step velocity analysis methods for VTI media. WeCompare non-hyperbolic traveltime curves provided by Alkhalifha&Tsvankin(1995), Siliqi&Bousquie(2000), Fomel(2007) and Aleixo&Schleicher (2009)with the actual traveltime curve.On the basis of further study about basic theory of developed anisotropy,anisotropic velocity analysis and high-resolution velocity analysis, we implementand enhance selective-correlation, phase correlation statistics and automaticnon-hyperbolic high-resolution velocity analysis methods with programme, andcompare the results of these new methods with traditional methods. The resultscertify the effectiveness of the new methods. We test on synthetic data and calculateerror to verify the accuracy of new methods. Then we introduce selective-correlation method into VTI media velocity analysis, and test on synthetic data using one-stepmethod. We compare the result of selective-correlation method with traditionalmethod to certify that it can increase the resolution in anisotropic velocity analysis.At last, we apply phase correlation statistical methods and automatic non-hyperbolicvelocity analysis method in VTI media, and test on synthetic and field data. Theresults show that these methods can obtain a high accuracy, and can be used inactual production.