Q Value Extraction Method And Analysis Of VSP Wave

When Seismic waves spread in the strata, as the rock strata are not totally elasticuneven medium, they make the part elastic energy of the seismic wave turn into heatenergy irreversible and the dissipation is happened, so it causes the energy and frequ-ency of the seismic wave attenuation and dispersion, reduces the resolution of seism-ic records. In the graph of the earthquake,the performances are the amplitude attenu-ation and phase aberration. The phenomenon of the amplitude decay what is caused ofthe media not totally elastic is known as absorption.Seismic wave attenuation of an important physical parameters is the medium ofthe absorption coefficient or the quality factor Q value, it describes the media not total-ly elastic characteristics. The laboratory and actual data measurement results indicatethat the quality factor and the rock property, fluid type and other factors. Therefore,th-e quality factor can be used as oil and gas reservoir recognition and hydrocarbon detec-tion a judgment sign. Therefore, the accurate inversion of the quality factor Q showof particularly important.The predecessors have put forward a lot of method that can estimate the qualityfactor Q. the method respectively realize in the time domain and the frequencydomain. The time domain method are the pulse amplitude attenuation method, pulserise time method and pulse to enhance the method; The representative of frequencydomain method are spectrum at analogy method, centroid frequency shift method andthe peak frequency offset method. Due to the time domain earthquake pulse amplitudeinformation is often influenced by the factors of scattering and geometric diffusion. Itis difficult to estimate the high precision Q value. Compared to frequency domain method, the impact factors are less, the inversion Q value is higher precision than inthe time domain.This paper expounds the reasons why the seismic wave which spreads in the visc-oelastic media will be frequency dispersion.The paper is also expounds the attenuate-ion mechanism and frequency dispersion model, Collectting predecessors’ material,in the based of them we summed up some kinds of the method of calculating the QThis paper selects two methods from them: Spectrum analogy method and CentroidFrequency Offset method. The paper describes the principle of the two methods, andon the basis of design simple model we establish the Q value estimation process, extra-ction Q value, complete is inversion, in the same time,we make the results of the twomethods compared with each other. The goal to estimate the Q value is to make comp-ensate of the seismic wave frequency dispersion, so this paper also make a simpledescription about the Q filtering.