塔中地区碳酸盐岩裂缝综合预测技术及其应用

塔中地区碳酸盐岩裂缝复杂多变,对储层的储渗性能、烃类运聚、产能起着至关重要的作用。针对塔中奥陶系裂缝发育的特点,形成了相干处理、应变量分析、数值模拟3种裂缝预测技术。高相干相表示较致密地层的反映;低相干相表示可能是岩溶或裂缝发育反映;极低值相干相表示各级断层的反映。应变量分析则是通过钻井标定,同时考虑地层厚度、岩性、裂缝发育方向等参数,对多期构造运动产生的裂缝的密度进行预测。数值模拟是利用应变量、曲率或其他地震属性做约束,应用随机模拟方法,确定裂缝的平面展布与发育程度。根据岩心观察裂缝的切割关系、充填成分以及充填序次,结合测井资料和以上3种技术的裂缝预测结果及区域构造应力场的分析,对塔里木盆地塔中16-塔中30井区奥陶系碳酸盐岩裂缝发育带进行了预测,这三项技术预测的结果与井区内实际钻井奥陶系碳酸盐岩岩心裂缝参数统计值基本吻合,证实了利用相干体、应变量分析和数值模拟技术综合预测塔中地区碳酸盐岩裂缝发育带是实用的,也是有效的。

Comprehensive fracture prediction technologies and their application to carbonate rocks in Tazhong area

Fractures of carbonate reservoirs are complex in Tazhong area and are critical to the poroperm characteristics of the reservoirs, hydrocarbon migration and accumulation, and productivity of wells. Taking into consideration the characteristics of fractures in the Ordovician carbonates in the Tazhong area, this paper presents three fracture prediction technologies, including coherence processing, strain analysis, and numerical simulation. High coherence facies indicates dense formation and low coherence facies may mean the existence of karst cavities or fractures, while extreme low coherence facies reflects faults of different grades. Strain analysis predicts the density of fractures caused by multi-phase tectonic movements, through drilling calibration and taking into consideration the parameters such as strata thickness,lithology, and fracture orientation. Constrained by strain magnitude, curvature, and other seismic attributes, the numerical simulation determines plane distribution and development of fractures through probabilistic simulation. According to the cutting relationship, filling components and filling orders of fractures observed in core samples, this paper predicted the fractured zones in the Ordovician carbonate reservoirs in Tazhong 16 -Tazhong 30 wellblock by combining logging data, fracture prediction results of the foregoing three technologies, and analysis of regional tectonic stress field. The prediction results are consistent with the statistics of fracture parameters of the cores taken from the Ordovician carbonate reservoirs in the field, showing that these technologies are practical and effective in predicting fractured zones in carbonates.