碳酸盐岩台内颗粒滩致密储层特征及体积压裂适应性研究

The study of tight intra-platform shoal reservoirs provides insights for future exploration and exploitation directed towards this type of petroleum play. Stimulated reservoir volume (SRV) is a new reconstruction method of tight sandstone reservoir. It is very important to apply the SRV technology for the exploitation of the tight carbonate shoal reservoir in theory and practical exploration. Based on the reservoir structural characterization, the changes of different shoal reservoir structures before and after the reconstruction will be presented, and 3D geological reservoir models will be established by the analysis methods of multi-scale pore structure. In order to clarify the distributions of fractures generated by volume fracturing and the conductivity within the fractures of different shoal reservoirs, the triaxial fracture test system and the fracture-conductivity experiments will be carried out. Then, the key influencing factors of the fracture distributions will be analyzed, and the experimental model of volume fracturing also will be proposed. Through the numerical simulation which incorporates the experimental results and geological models, the adaptability of a vertical well or multi-stage horizontal well stimulated by volume fracturing in tight intra-platform shoal reservoir will be discussed.The applicable conditions of volume fracturing in tight intra-platform shoal reservoir will be identified. At last, the results of the experiments and the numerical models will be verified by the complex fracture systems after the volume fracturing which has been monitored by the micro-seismic technology in the field. Meanwhile, the key factors influencing the large-scale fracturing will be recognized. A reconstruction method of tight carbonate shoal reservoir, which integrates geological research, laboratory experiment, theoretical prediction and field application, will be established.

碳酸盐岩台内颗粒滩致密储层蕴藏着丰富的油气资源，是油气勘探开发的新领域；体积压裂是致密砂岩储层改造新方法；探索将体积压裂技术应用到碳酸盐岩颗粒滩致密储层改造中，具有重要理论和现实意义。项目从储层结构表征入手，利用多尺度孔隙结构分析技术，立体呈现不同类型颗粒滩储层结构压前、压后变化规律，建立储层三维地质模型。同时，开展真三轴水力压裂裂缝延展模拟实验和清水压裂裂缝导流能力实验，分析不同类型颗粒滩储层压裂裂缝展布特征及导流能力，确定影响水力压裂的关键因素，建立体积压裂实验模型。利用实验模型和储层地质模型，通过数值模拟方法，开展直井体积压裂和水平井多段多簇体积压裂适应性研究，确定台内颗粒滩致密储层体积压裂的适用条件。最后，采用微地震技术监测现场井压后缝网形态，验证体积压裂实验结果和评价模型，明确影响大规模现场压裂的关键因素，为碳酸盐岩颗粒滩致密储层高效开发，提供理论和实验基础。

碳酸盐岩台内颗粒滩致密储层蕴藏着丰富的油气资源，是油气勘探开发的新领域，将体积压裂技术应用到碳酸盐岩颗粒滩致密储层改造中，具有重要理论和现实意义。本项目建立了基于扫描电镜-恒压压汞-核磁共振的颗粒滩储层微观特征多方法表征技术，对深埋藏碳酸盐岩储集空间发育特征进行了直观定量表征，研究发现台内滩致密储层的孔渗相关性较差，但是rapex与进汞压力、最大及平均孔喉半径之间相关性良好。分析了碳酸盐岩物性与沉积组构之间的关系，发现具有藻黏结结构的深埋藏微孔碳酸盐岩较不具有黏结结构的碳酸盐岩有更好的孔渗性。改进了基于核磁共振的渗透率计算方法，在计算渗透率的Coates模型中引入受控于样品沉积组构且可以直接获取的调节参数，提高了渗透率计算精度。 建立了针对碳酸盐岩微孔的孔隙综合分类方案，将深埋藏微孔碳酸盐岩中的孔隙划分为赋存于具有较大孔渗的藻灰（白云）岩半自形-他形微晶之间的孔隙、赋存于碎屑灰岩多面体微晶之间的孔隙以及赋存于菱形白云石微晶之间的孔隙。研究证实体积压裂技术在碳酸盐岩颗粒滩储层中具有较好的应用效果，压裂之后有新的微裂缝产生，裂缝之间相互连接可形成新的缝网。台内颗粒滩类型、地应力和天然裂缝共同对体积压裂效果产生影响。缝合线和方解石脉被证明是水力压裂过程中的优势破裂面。清水压裂裂缝导流能力实验发现裂缝粗糙程度会影响自支撑裂缝的初始导流能力，自支撑裂缝在低闭合压力下导流效果优于支撑剂裂缝。随着闭合压力的增大，自支撑裂缝导流能力指数型下降，而支撑剂裂缝导流能力平稳下降并逐渐优于自支撑裂缝。通过数值模拟，建立了复杂裂缝的数学描述方法并形成快速算法，分析了Z型裂缝的不稳态压力和流量分布，探讨了不同裂缝参数对压力的影响。