优势渗流层段测井评价及应用

Logging Identification and Evaluation of Dominant Seepage Intervals

有效识别砂岩油藏长期注水开发形成的优势渗流通道,是现阶段老油田提高采收率急需解决的难点之一。已有研究中有关优势渗流通道的识别方法,多是基于井间或井组间的动态监测,或者利用动态与静态资料相结合,通过复杂的算法模型来评价和预测。本文针对目标砂体本身较强的非均质性以及长期注水开发的改造,储层的渗透性与孔隙度相关性差,而主要受控于孔隙结构的储层特征,通过分析优势渗流层段形成的微观机理和主导因素,将储层微观孔隙结构变化及宏观非均质程度作为两大评定因素,构建优势渗流层段综合评价指数,进而建立两大因素的测井表征方法,逐步实现基于核磁共振测井与常规测井资料的优势渗流层段识别与评价。将研究区39口井分别进行优势渗流指数处理计算,通过与实际实施井的对比,发现冲刷较强,水淹程度较高的砂体部位,S d指数都达到20以上,因此确定S d≥20即为优势渗流层段。该指标对区域优势渗流层段的识别精度可达73%。

How to effectively identify the dominant seepage channels formed by long-term waterflooding in sandstone reservoirs is one of the difficult problems to be solved urgently at present.The identification methods of the dominant seepage channels in the existing researches are mostly based on the dynamic monitoring between wells or between well groups,or the combination of dynamic and static data to evaluate and predict through complex algorithm models.In view of the strong heterogeneity of the target sand body and the reconstruction of long-term waterflood development,the permeability of the reservoir is poorly correlated with the porosity,which is mainly controlled by the characteristics of the pore structure of the reservoir.By analyzing the microscopic mechanism and leading factors of the formation of the dominant seepage intervals,the change of the microscopic pore structure and the degree of macroscopic heterogeneity of the reservoir are taken as the two major assessment factors.The comprehensive evaluation index of the dominant seepage interval was established,and then the logging characterization method of the two factors was established,and the identification and evaluation of the dominant seepage interval based on NMR and conventional logging data was gradually realized.Through the comparison with the actual wells,it is found that the S d index of sand body parts with strong erosion and high flooding degree is above 20,so S d≥20 is determined as the dominant seepage interval.The identification accuracy of this index for regional dominant seepage interval can reach 73%.