Attenuation anisotropy linked to velocity anisotropy: Theory and ultrasonic experiment

Abstract

We perform an ultrasonic experiment on anisotropy of wave propagation in the model constructed from plexiglas plates, with oil saturation and without any saturation. We determine the directional dependencies of P-and S-waves attenuations and velocities and estimate Thomsen-style parameters for attenuation Q ε , Q δ , and Q γ as well asThomsen's velocity parameters. We develop a theory that predicts certain relationship between anisotropies of P-, SH-and SV-wave attenuation and velocity in transversely isotropic (TI) media due to aligned fracture set. Taking into account the interplay of the velocity and attenuation anisotropies, we develop the effective TI model of the attenuative fractured medium fitted to the experimental data. We derive formulas for the parameters Q ε , Q δ , and Q γ in terms of complex-valued weaknesses that relates these parameters to fractured medium parameters. We found out that the ratio of the symmetry-axis P-and S-wave attenuations S P Q Q / and the parameter Q δ are interlinked and strongly dependent of the fluid type in cracks that is confirmed by the experiment. The value of Q δ is much greater for dry-crack medium than for wet-crack medium, that is correlated with the S P Q Q / -ratio, which is on the contrary larger in wet-crack medium and smaller in drycrack medium. This is in accordance with laboratory measurements at ultrasonic frequencies of P-and S-wave quality factors.

Generalization of Schoenberg's linear slip model to attenuative media: Physical modeling versus theory

“…, and (Chichinina et al, 2007a(Chichinina et al, , 2007b(Chichinina et al, , 2008. By the same manner, we obtain the approximations for the SV-and SH-wave attenuations:…”

“…The imaginary parts of the weaknesses are interpreted in the terms of the equant-porosity Hudson's model, in which attenuation is caused by the local fluid flows between aligned cracks and randomly distributed pores (Pointer et al, 2000). Now we continue the study of attenuation anisotropy (or the Q-anisotropy) in the LS model started in (Chichinina et al, 2007a(Chichinina et al, , 2007b(Chichinina et al, , 2008 with developing the theoretical formalism and testing its validity on the data of the laboratory ultrasonic experiment. Attention is given to justification of the replacement of the real-valued weaknesses by complex-valued and possible attenuation mechanisms.…”

Estimating applicability of the displacement-discontinuity model using experimental data on measurements of elastic-wave velocities

“…3. Его продолжением в сторону низких давлений можно считать график 13 ( ) c P Δ для модели из пласти-нок плексигласа с волнистыми поверхностями, по-строенный нами по данным экспериментальной рабо-ты [Гик, Бобров, 1996], представленным в публикаци-ях [Chichinina et al, 2007[Chichinina et al, , 2009a в терминах модели Шонберга LS. В эксперименте Л.Д.…”

Estimation of fracture-strike azimuth by QVOA analysis validated by simulated seismic data of physical modeling

“…QVOA analysis for fractured reservoirs is based on the use of the generalized Linear Slip model predicting P-wave attenuation as a function of the fracture-strike direction, i.e., Q -1 (θ, φ-φ0)-function, where θ is the wave-incidence angle, φ is the azimuth angle of the source-receiver line, and φ0 is the azimuth of the fracture strike (as shown in Fig. 2), e.g., Chichinina et al (2006aChichinina et al ( , 2006bChichinina et al ( , 2007aChichinina et al ( , 2007bChichinina et al ( , 2009aChichinina et al ( , 2009bChichinina et al ( , 2009c. QVOA method is based on the fitting of the Q -1 (θ, φ-φ0)-function to the seismic data on attenuation.…”