The Study On Seismic Absorption And Attenuation Characteristics In The Carbonate Rocks Outcrop

The stratum’s quality factor Q is an important parameter to describe rock elasticity, andit is also one of the vital symbols to indicate the hydrocarbon potential of stratum. This thesisdiscusses three theories of the seismic absorption and attenuation: the viscoelastic mediumtheory, the scattering theory and Biot theory and squirt flow theory. Besides, it analyzes andsummarizes the influential factors of seismic absorption and attenuation.In this paper, the existing Q value calculation formulas are compared and summarized,especially Li Qingzhong and other four empirical formulas. In all empirical formula, LiQingzhong Q-V empirical formula can reflect the general trend of scattered point data,therefore this research mainly adopts the Li Qingzhong formula to estimate the Q value forthe micro logging data of Sichuan Basin Zhenba area.This paper analyzes the seismic absorption and attenuation forward modeling based onthe constitutive equation of the generalized Maxwell element. Analysis shows that when notconsidering formation absorption effect on seismic waves, stratigraphic layering effect ismore obvious, and the seismic energy with the offset increasement attenuates slowly,meanwhile its amplitude attenuation is relatively slow; when considering formationabsorption effect on seismic waves, stratigraphic layering effect is relatively poor, and theseismic energy with the offset increasement attenuates fast, meanwhile its amplitudeattenuation is relatively fast.This paper, on the basis of the theoretical analysis for a detailedseismic absorption and attenuation and the quantitative estimation for quality factor, carriesout the study of seismic absorption and attenuation characteristics in the carbonate rocksoutcrop near-surface using the micro-logging data, and explores the causes of the low qualityof seismic data. The results show that: comparing with sandstone, mudstone and sand-mudinterbed outcrop area, the quality factor of the low-velocity layer in the limestone outcrop islower, meanwhile formation absorption and attenuation characteristics are stronger; but thequality factor of the reducing velocity layer and high-velocity layer are relatively high,meanwhile formation absorption and attenuation characteristics are weaker. Strongabsorption and attenuation in the limestone outcrop near-surface is probably one of thecauses of the low quality seismic data in the carbonate rock outcrop.