SEISMIC SIGNATURES OF PORE CONNECTIVITY

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2014-08

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Abstract

The goal of this dissertation is analyzing medium parameters’ influence on seismic signatures, especially pore connectivity. Firstly, I use the Zoeppritz equation to analyze reflection coefficient's sensitivity to eight medium parameters; results show they all have significantly different sensitivity.

Friability is an empirical parameter introduced in General Singular Approximation (GSA) to measure the extent of pore connectivity that has the numerical range from 0 to 1. In the second part, with other assumed medium parameters, calculation results show friability has observable seismic signatures. Most of them have very large, non-monotonic, and nonlinear variations to friability. Specifically, I observe: 1, as friability increases, most stiffness-tensor components decrease; 2, most extended Thomsen's parameters decrease as friability increases. ϵ2, γ2, δ2, and δ3 in gas-saturated medium and ϵ1, δ2, and δ3 in water-saturated medium are very sensitive to friability, while others are not; 3, there are sophisticated relationships between phase velocities and friability out of the symmetry plane, especially for S\textsubscript{2} wave; 4, friability equals zero corresponds to the largest critical angle, while friability equals 1 corresponds to the smallest. Critical angle mostly increases as azimuth angle increases; 5, normal incident PP reflection coefficient is enough to detect the friability variation in gas-saturated medium. On the other hand, azimuthal variation of PP reflection coefficient also depends strongly on friability in both media.

Lastly, as a comparison to GSA, poroviscoelasticity is introduced by synthesizing Biot theory and viscoelasticity because Biot theory assumes completely connected pore space. The influence of frame inelasticity on poroviscoelastic wave dispersions, attenuations, and reflection and transmission coefficients are computed and analyzed in detail. Results show frame inelasticity has considerable influence on reflection and transmission coefficients in certain frequencies and incidence angles.

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Keywords

Seismic, Pore connectivity, Zoeppritz, Anisotropy, Poroviscoelasticity, Reflection coefficient

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