In order to eliminate the effect of ocean bottom topography on seismic wave field,we transformed curved(x,z)coordinate system grids into rectangular(ξ,η)coordinate system grids and derived a 2-D scalar acoustic ...
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In order to eliminate the effect of ocean bottom topography on seismic wave field,we transformed curved(x,z)coordinate system grids into rectangular(ξ,η)coordinate system grids and derived a 2-D scalar acoustic wave equation in theξ,η*** seismic wave field collected at the sea surface was downward continued to the ocean bottom by the inverse finite difference method with the water velocity and then was reversely continued to the ocean surface by the finite difference method using the layer velocity from just below the ocean bottom in the(ξ,η)*** calculations and practical application show that this method can not only remove the reflection travel time distortion but also correct the dynamic parameter changes caused by the ocean bottom *** inverted velocity after wave field continuation is much more accurate than before continuation and the image section was greatly improved compared to the original wave field.
Ultrasonic velocities of a set of saturated sandstone samples were measured at simulated in-situ pressures in the *** samples were obtained from the W formation of the WXS Depression and covered low to nearly high por...
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Ultrasonic velocities of a set of saturated sandstone samples were measured at simulated in-situ pressures in the *** samples were obtained from the W formation of the WXS Depression and covered low to nearly high porosity and permeability *** brine and four different density oils were used as pore fluids,which provided a good chance to investigate fluid viscosity-induced velocity *** analysis of experimental observations of velocity dispersion indicates that(1)the Biot model can explain most of the small discrepancy(about 2–3%)between ultrasonic measurements and zero frequency Gassmann predictions for high porosity and permeability samples saturated by all the fluids used in this experiment and is also valid for medium porosity and permeability samples saturated with low viscosity fluids(less than approximately 3 mP·S)and(2)the squirt flow mechanism dominates the low to medium porosity and permeability samples when fluid viscosity increases and produces large velocity dispersions as high as about 8%. The microfracture aspect ratios were also estimated for the reservoir sandstones and applied to calculate the characteristic frequency of the squirt flow model,above which the Gassmann’ s assumptions are violated and the measured high frequency velocities cannot be directly used for Gassmann’s fluid replacement at the exploration seismic frequency band for W formation sandstones.
In this article,based on the acoustic measurements of core samples obtained from the low to medium porosity and permeability reservoirs in the WXS Depression,the densities and P and S wave velocities of these core sam...
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In this article,based on the acoustic measurements of core samples obtained from the low to medium porosity and permeability reservoirs in the WXS Depression,the densities and P and S wave velocities of these core samples were *** based on these data,a series of elastic parameters were *** the basic theory and previous pore fluid research results,we derived a new fluid identification factor(F).Using the relative variations,Ag/w and Ao/w,of the elastic parameters between gas and water saturated samples and between oil and water saturated samples,λρ,σHSFIF,Kρ,λρ-2μρ,and F as quantitative indicators,we evaluate the sensitivity of the different fluid identification factors to identify reservoir fluids and validate the effects by *** confirm that the new fluid identification factor(F) is more sensitive for distinguishing oil and water than the traditional method and is more favorable for fliud identification in low to medium porosity and permeability reservoirs.
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