Currently,most rock physics models,used for evaluating the elastic properties of cracked or fractured media,take into account the crack properties,but not the background anisotropy.This creats the errors of in the ani...Currently,most rock physics models,used for evaluating the elastic properties of cracked or fractured media,take into account the crack properties,but not the background anisotropy.This creats the errors of in the anisotropy estimates by using fi eld logging data.In this work,based on the scattered wavefi eld theory,a sphere-equivalency method of elastic wave scattering was developed to accurately calculate the elastic properties of a vertical transversely isotropic solid containing aligned cracks.By setting the scattered wavefi eld due to a crack equal to that due to an equivalent sphere,an eff ective elastic stiff ness tensor was derived for the cracked medium.The stability and accuracy of the approach were determined for varying background anisotropy values.The results show that the anisotropy of the eff ective media is aff ected by cracks and background anisotropy for transversely isotropic background permeated by horizontally aligned cracks,especially for the elastic wave propagating along the horizontal direction.Meanwhile,the crack orientation has a signifi cant infl uence on the elastic wave velocity anisotropy.The theory was subsequently applied to model laboratory ultrasonic experimental data for artifi cially cracked samples and to model borehole acoustic anisotropy measurements.After considering the background anisotropy,the model shows an improvement in the agreement between theoretical predictions and measurement data,demonstrating that the present theory can adequately explain the anisotropic characteristics of cracked media.展开更多
基金supported by the National Natural Science Foundation of China (No. 41821002)the Fundamental Research Funds for the Central Universities (Nos. 18CX02065A,20CX06046A)+3 种基金the Young Elite Scientist Sponsorship Program by the China Association for Science and TechnologyMajor Scientifi c and Technological Projects of CNPC (No. ZD2019-183-004)Qingdao Postdoctoral Applied Research Project (No. qdyy20190079)China Postdoctoral Science Foundation (No. 2020M672171)。
文摘Currently,most rock physics models,used for evaluating the elastic properties of cracked or fractured media,take into account the crack properties,but not the background anisotropy.This creats the errors of in the anisotropy estimates by using fi eld logging data.In this work,based on the scattered wavefi eld theory,a sphere-equivalency method of elastic wave scattering was developed to accurately calculate the elastic properties of a vertical transversely isotropic solid containing aligned cracks.By setting the scattered wavefi eld due to a crack equal to that due to an equivalent sphere,an eff ective elastic stiff ness tensor was derived for the cracked medium.The stability and accuracy of the approach were determined for varying background anisotropy values.The results show that the anisotropy of the eff ective media is aff ected by cracks and background anisotropy for transversely isotropic background permeated by horizontally aligned cracks,especially for the elastic wave propagating along the horizontal direction.Meanwhile,the crack orientation has a signifi cant infl uence on the elastic wave velocity anisotropy.The theory was subsequently applied to model laboratory ultrasonic experimental data for artifi cially cracked samples and to model borehole acoustic anisotropy measurements.After considering the background anisotropy,the model shows an improvement in the agreement between theoretical predictions and measurement data,demonstrating that the present theory can adequately explain the anisotropic characteristics of cracked media.
