摘要
Fracture-cave reservoirs in carbonate rocks are characterized by a large difference in fracture and cavity size,and a sharp variation in lithology and velocity,thereby resulting in complex diffraction responses.Some small-scale fractures and caves cause weak diffraction energy and would be obscured by the continuous reflection layer in the imaging section,thereby making them difficult to identify.This paper develops a diffraction wave imaging method in the dip domain,which can improve the resolution of small-scale diffractors in the imaging section.Common imaging gathers(CIGs)in the dip domain are extracted by Gaussian beam migration.In accordance with the geometric differences of the diffraction being quasilinear and the reflection being quasiparabolic in the dip-domain CIGs,we use slope analysis technique to filter waves and use Hanning window function to improve the diffraction wave separation level.The diffraction dip-domain CIGs are stacked horizontally to obtain diffraction imaging results.Wavefield separation analysis and numerical modeling results show that the slope analysis method,together with Hanning window filtering,can better suppress noise to obtain the diffraction dip-domain CIGs,thereby improving the clarity of the diffractors in the diffraction imaging section.
碳酸盐岩缝洞型储层所含缝、洞尺度差异大、岩性和速度变化剧烈,造成复杂的绕射响应特征。部分缝洞体尺度小产生的绕射能量较弱,在成像剖面上被连续反射层掩盖,而难以识别。基于此,本文发展了一种倾角域道集的绕射波成像方法,提高对成像剖面上小尺度绕射构造的分辨能力。借助高斯束偏移技术抽取倾角域成像点道集,根据在倾角域道集上绕射同相轴拟线性、反射能量拟抛物的几何形态差异,基于斜率分析方法实现波场分离,并采用汉宁窗函数提高绕射波分离效果,将分离后的绕射波倾角域道集水平叠加得到绕射波成像结果。理论分析和数值模型测试结果表明:在窗函数的基础上,应用基于斜率分析的波场分离方法得到的绕射波倾角域道集能够更好的压制噪声,叠加后的绕射波成像剖面中绕射构造更加清晰。
基金
funded jointly by the National Natural Science Foundation of China(No.41104069)
Shandong Province Higher Educational Science and Technology Program(No.J17KA197)
Open Foundation of Shandong Provincial Key Laboratory of Depositional Mineralization&Sedimentary Minerals of Shandong University of Science and Technology(No.DMSM2018018)
Chunhui Research Foundation of Shengli College,China University of Petroleum(No.KY2017007)。
