基于全方位地震成像与叠前反演裂缝预测技术及应用

Full Azimuth Imaging and Pre-stack Inversion for Fractured Reservoirs Prediction and the Application

利用宽方位地震反演预测裂缝储层,传统方法是采用分扇区或分方位进行地震数据处理,但其无法得到地下真实角度域信息,精度和分辨率较低。应用全方位角度域分解与成像,将地震成像转移到地下,得到共倾角道集和共反射角道集。将共倾角道集,进行镜像成像和离散成像,不仅提高了地震资料的信噪比和成像精度,而且对断层、裂缝和溶洞等地质现象也能较清楚的识别。将共反射道集进行反演,通过计算截距、斜率和各向异性梯度等的参数,完成对裂缝密度和方向分布的预测,进而实现裂缝储层的识别和有利区预测。在塔里木盆地YB1井区碳酸盐岩裂缝储层的预测中,取得了较好的应用效果,成功预测出该区裂缝主要在构造高部位和断层附近发育。在构造隆起的东北部,裂缝和构造叠合关系好,是油气成藏的有利地区,也是该区油气进一步勘探开发的重点目标区。

During the application of wide azimuth seismic data to forecast the fractured reservoirs, the ordinary processing procedure is sectoring with different azimuth. However, the precision and resolution of this processing method are low because of its disability to get the real subsurface angel information which can result in the lack of geological information. In order to improve the signal to noise ratio and the imaging precision, the seismic data can be decomposed in the full azimuth angle domain and two type angle gathers can be generated which are directional angle gathers and reflection angle gathers. For directional angle gathers based on the application of mirror and dis- crete imaging, the final seismic data can reflect geologic phenomena including faults, fractures and caves. On an- other aspect, reflection angle gathers can be inverted and the reflecting anisotropy and fluid parameters, such as in- tercept, slope and gradient, can be calculated, then the fractures distribution density and direction can be forecasted. This new technique has been successfully applied in carbonate fractured reservoirs prediction of YB1 well block in Tarim Basin. The research results show that the north-eastern part of the study area with abundant frac- tured reservoirs development and favorable structure condition is the important aim for next exploration and development.