乌石东区成岩演化数值模拟与孔隙度预测

Numerical simulation of diagenetic evolution and porosity prediction in eastern area of Wushi Sag

乌石东区已发现的商业性油田主要形成于复杂陆相沉积环境,受构造、沉积和成岩作用综合影响,储层非均质性强,油藏渗流特征复杂,直接影响着油田的开发方案制定。因此,有必要开展储层物性主控因素分析,从理论上和技术上实现甜点区预测。研究采用成岩数值模拟的方法,基于成岩环境参数,应用化学动力学模型,通过对镜质组反射率、古地温、伊/蒙混层中蒙皂石层含量和石英自生加大的模拟,加权平均得到成岩指数。根据成岩指数的变化对储层成岩阶段及孔隙度横向展布规律进行预测。模拟结果表明,乌石东区成岩阶段主要为中成岩A1-A2期,凹陷中心成岩作用较强,向北逐渐减弱。综合沉积、成岩等认识,建立孔隙度预测模型,对孔隙度进行平面预测,预测结果表明:顺物源方向,随埋深增大,储层物性变差,同成岩作用变化趋势一致。

The commercial oil fields discovered in the eastern area of Wushi Sag in recent years are mainly formed in a complex continental sedimentary environment,which was influenced by the tectonic movement,sedimentation and diagenesis.The reservoir in the oilfields of the study is characterized by a strong heterogeneity,complex reservoir seepage mechanism,which affects the development program Therefore,the analysis of the main controlling factors of the reservoir physical properties is extremely necessary,which can help the decision-makers to predict the sweet spot area theoretically and technically.In this paper,the method of numerical simulation of diagenetic evolution was adopted,in which the diagenesis index was obtained by the simulation of vitrinite reflectance,paleotemperature,smectite content in illite/smectite mixed layer,and quartz autogenesis increase based on the diagenetic environment parameter and chemical kinetic model.Moreover,the diagenetic stage and the lateral distribution of porosity were predicted based on the change of the diagenetic index.The results show that the diagenesis stage in the eastern area of Wushi Sag is the middle diagenesis stage A1-A2,and the diagenesis in the central sag is strong and gradually weaken.Combining the understanding of sedimentary and diagenesis,establishing the porosity prediction model and predicting it in horizon,the results indicate that:Following the source of sedimentary,the reservoir physical properties worsen with increasing burial depth,which is consistent with the change trend of diagenesis.