绕射信息提取技术及其在致密砂岩断裂系统识别中的应用

Diffraction information extraction and its application to the identification of tight sandstone fracture systems

致密砂岩储层的断裂系统和裂缝发育的准确描述是油气勘探开发过程中的关键问题之一,其中发育的小尺度断裂、裂缝等地质异常体通常会在地震波场传播中产生绕射,这些绕射信息在保幅偏移后能够得到较好地保留。中值滤波技术能够利用反射波与绕射波的空间相关性差异,进行绕射信息提取。在利用中值滤波技术提取的绕射波信息基础上,进一步利用绕射波的空间相关性,采用绕射特征增强处理技术压制部分噪声,突出边缘绕射信息,从而得到更加直观的裂缝发育系统。将该技术用于鄂尔多斯盆地某实际地震资料的处理,结果表明,该技术能够有效提取断裂信息,绕射信息增强结果能够识别出研究区存在的丰富小尺度断裂,较好地刻画了断裂系统的空间展布,对致密气储层研究具有重要意义。

The characterization of faults and fractures in tight sand gas reservoirs is an important issue in the development of oil and gas exploration.Small-scale faults,fractures,and other minor geological anomalies usually produce diffraction waves,which can be retained almost completely after amplitude-preserved migration.The median filtering method is effective in extracting the diffraction information by calculating the spatial correlation difference between the reflections and diffractions.A workflow for diffraction information separation based on the median filtering method was proposed,which was subsequently tested on tight sand gas reservoirs data in the Ordos Basin,China.In this work,we first illustrated the workflow s ability in reflection prediction and diffraction extraction.We then employed the spatial correlation of the diffraction waves to enhance the diffraction features.This procedure was found to suppress noise and highlight the edge diffraction information;this provided a more intuitive fracture development system than the traditional diffraction profiles.The results of the application showed that the proposed method can extract the fracture information effectively;further,it can intuitively depict the spatial display of fracture systems,which are of great significance in tight sand gas reservoirs.