致密油储层岩石复杂孔隙结构定量表征及含油性评价

Tight oil is considered as a new type of feasible replace resources, and tight oil exploration and development has become another hot spot beside shale gas all over the world. Studying on methods of evaluating microscopic pore structure and evaluating oiliness in tight oil reservoirs, is of great importance in planning the exploration direction, and improving development efficiency. The Triassic Chang 6 to Chang 7 Formation of Ordos basin, which is rich in tight oil, is chosen as a case to be studied in this project. After tight oil reservoir types are analyzed, the core laboratory experiments and numerical simulation method based on random walk theory are combined to study the nuclear magnetic resonance (NMR) response mechanism of different types of reservoir rocks. Combining with NMR, atomic force microscope (AFM) and constant-rate mercury injection experiments, the nanoscale and micro-nanoscale microscopic pore structure and pore-throat configuration relationship of tight oil sands are researched, and the critical pore radius lower limit is acquired. Based on the core experimental measurements of NMR and mercury injection, the hydrocarbon calibration method for NMR T2 distribution is proposed and the model of constructing capillary pressure curve from NMR logging is established to quantitatively evaluate formation pore structure. Combining with the nanoscale and micro-nanoscale pore throat theory and core experimental measurements, total oil saturation, movable oil saturation and immobile oil saturation are estimated from NMR capillary pressure curves. With the experimental measurements and numerical simulation method, rock electric conductivity that affected by the pore structure and wettability is studied, and the oil saturation estimation model under complicated formation condition is optimized. These research results can offer technical support in evaluating the validity of tight oil reservoirs and predicting resource potentiality, and these are also usable in calculating dependable tight oil reservoirs evaluation parameters.

致密油作为非常现实的石油接替资源，是继页岩气之后全球非常规油气勘探开发的新热点。开展微观孔隙结构定量表征和含油性评价研究，对指导致密油勘探方向，提高开发效率具有决定作用。本项目拟以鄂尔多斯盆地三叠系长6-长7致密油层为对象，在对致密油储层类型进行分析的基础上，采用岩心实验和数值模拟相结合的方法，研究不同类型储层的核磁共振响应机理；结合核磁共振、原子力显微镜和恒速压汞实验，研究致密油储层岩石纳米、微纳米尺度的孔隙微观结构和孔-喉配置关系，确定油层临界孔隙半径下限；基于岩心压汞和核磁共振实验，确定含烃岩石核磁T2谱形态校正方法，在此基础上，建立核磁毛管压力曲线构造模型以定量评价储层孔隙结构；结合纳米级、微纳米级孔喉理论和岩心实验，确定储层的含油（总含油、可动油和束缚油）饱和度；结合岩心实验和数值模拟结果，研究孔隙结构和润湿性双重影响下岩石的导电特性，优化复杂地层条件下的含油饱和度评价模型。本项研究成果即为致密油储层有效性评价和潜力预测提供技术支撑，同时也可为计算致密油储层关键参数提供可靠的基础资料。

致密油作为非常现实的石油接替资源，是继页岩气之后全球非常规油气勘探开发的新热点。开展微观孔隙结构定量表征和含油性评价研究，对指导致密油勘探方向，提高开发效率具有决定作用。本项目自2013年8月获得立项以来，以国内鄂尔多斯盆地、四川盆地和松辽盆地岔路河断陷等典型致密储层为研究对象，采用岩石物理实验和数值模拟相结合的方法，研究了致密储层核磁共振测井响应机理，分析了孔隙含烃对核磁共振T2谱形态特征的影响，在此基础上，建立了致密含烃储层核磁共振T2谱形态校正方法。基于岩心高压压汞和核磁共振实验数据，建立了利用核磁共振测井构造毛管压力曲线，并确定储层孔喉半径分布，以评价致密储层孔隙结构的方法和模型。在此基础上，研究了核磁共振测井在致密裂缝型储层孔隙结构评价中的局限性，并提出了利用从微电阻率扫描成像测井（FMI）中获取的孔隙度频率谱构造伪毛管压力曲线，并用以评价裂缝型储层孔隙结构的方法和模型，在此基础上，建立了储层总渗透率评价模型。通过对岩心核磁共振、高压压汞、铸体薄片以及电阻率实验的综合分析，研究了致密储层孔隙结构、孔喉配位数与岩电参数m和n之间的相关关系，提出孔隙结构越好的岩石，相应的胶结指数m越高，饱和度指数n越低，反之，孔隙结构越差的岩石，相应的胶结指数m越低，饱和度指数n越高。在此基础上，利用最优的T2截止值将核磁共振T2谱划分为两个孔隙组分，采用大孔隙组分和小孔隙组分百分含量的比值来表征岩石孔隙结构，并利用其优化饱和度指数n的模型。同时，基于理论分析的基础上，建立了致密储层胶结指数m与孔隙度之间的理论关系，以从孔隙度中计算可变的胶结指数m。利用变化的胶结指数m和饱和度指数n，优化了致密储层含油饱和度计算模型，大大提高了致密储层饱和度评价精度。相关研究成果共发表国际SCI论文7篇、申请国家发明专利3项、参加国际会议并宣读论文3项，荣获刘光鼎地球物理青年科学技术奖等奖励3次，圆满完成了项目立项时设定的各项指标。