塔里木盆地沙漠地区近地表衰减介质对深层-超深层缝洞储集体成像影响OA

The loose structures and serious weathering and denudation of the near-surface layers in desert areas have a significant absorbing and attenuating effect on seismic wave,greatly reducing the imaging accuracy and identification reliability of deep to ultra-deep fractured-vuggy reservoirs in the Tarim Basin.Additionally,there is little research on the quantitative characterization of the comprehensive influence of this effect on reservoir imaging features.This paper carries out forward modeling of fractured-vuggy reservoirs under the condition of near-surface strong attenuation by means of the pseudo-spectral method based on the generalized viscoelastic wave equation,and then comparatively analyzes the reflection characteristics and imaging results of deep to ultra-deep fractured-vuggy reservoirs across varying near-surface attenuation intensities and thicknesses.The following results are obtained.First,under the condition of near-surface strong absorption and attenuation,two parallel reservoirs require a minimum separation of 1/2 wavelength,so that the seismic imaging can effectively tell the difference between different fractured-vuggy reservoirs.Second,under the condition of surface strong attenuation,low-velocity reservoirs exhibit higher resolution than high-velocity ones,and the reservoir combinations with different velocities will interfere each other,and thus reduce the seismic imaging resolution.Third,under the condition of surface strong absorption and attenuation,the displacement distance of reservoir imaging is proportional to the thickness of absorption and attenuation layer.Fourth,the near-surface absorption and attenuation effect can shift the correspondence between the"beadlike"imaging phase and the top and bottom interfaces of reservoir.In conclusion,this study further understands the impact of near-surface loose structures on seismic wave reflection characteristics and imaging accuracy of deep to ultra-deep fractured-vuggy reservoirs,and provides guidance and reference for understanding the imaging patterns of fractured-vuggy reservoirs.