缝洞型碳酸盐岩油藏多相流体流动规律与剩余油形成机理研究

The annually increasing proved reserves and production promote that fractured-vuggy carbonate reservoirs serve as a significant substitution of hydrocarbon resources in West China. The features of fractured-vuggy carbonate reservoir include the ultra-low permeability of carbonate rocks, the co-existence of large fractures and vugs, and the fluid pipe flow. Most of previous emphases were placed on fluid flow characterization using the systemic theory of clastic reservoirs. The pipe flow characteristics were considered in some studies, while the model assumption was too ideal, which causes that the field application is limited and the studies do not work well for the evaluation of well productivity. Based on the fractures and vugs distribution of typical fractured-vuggy carbonate reservoirs in China, fracture system models and fractured-vuggy system models will be fabricated with a consideration of the size, connected mode and conjunction of fractures and vugs. Combining physical simulation with reservoir simulation executions, the governing factors of oil-water and oil-gas interfaces are discussed. And thus, the fluid pipe flow mechanisms are demonstrated in fractured-vuggy carbonate reservoir. The theory of multi-phase pipe flow is used to quantitatively characterize fluid flow, and the mathematical model is established. Based on the complex fractured-vuggy network models that are more in accordance with reservoir features, the distribution and formation mechanisms of remaining oil are illustrated through further laboratory experiments. This research work could provide a practical guide on the recovery of remaining oil and the implementation of EOR projects in fractured-vuggy carbonate reservoirs.

我国缝洞型碳酸盐岩油藏油气探明储量和产量逐年增加，已成为西部油气资源的重要接替。该类油藏存在基质渗流能力极弱、大裂缝和溶洞发育、流体管流特征明显等特点。目前研究大多借鉴碎屑岩的渗流理论，部分考虑了缝洞型介质流体管流特征，但模型假设较理想，生产应用中预测误差较大，难以有效指导油井产能评价。本课题拟根据我国典型缝洞型油藏裂缝和溶洞分布特征，制作不同缝洞尺度、缝-缝和缝-洞连通模式、缝-缝和缝-洞组合关系的裂缝系统和缝洞系统物理模型，通过室内实验和模拟计算，开展油水、油气流动两相界面影响因素分析，揭示缝洞型油藏流体管流流动规律；应用多相管流理论分析与描述裂缝和溶洞中流体流动特征，建立缝洞型油藏流体流动数学评价模型；基于上述研究成果，利用与实际储层相似的多缝多洞组合缝洞网络模型，通过室内实验明确多因素影响的剩余油分布特征，揭示剩余油形成机理，为缝洞型油藏剩余油挖潜和提高采收率技术应用提供科学依据。

缝洞型碳酸盐岩油藏地质特征复杂，主要体现在缝和洞的多尺度性、分布多样性、连通及组合复杂性。复杂的地质特征决定了该类介质中流体流动的复杂性，尤其是对于多相流动过程。开展缝洞型油藏多相流动规律研究，对于该类油藏的高效可持续开发具有重要指导意义。本项目主要开展了缝洞型油藏多相流动基础理论研究，涉及缝洞型介质油-水和油-气两相流理论、底水驱油规律、注气驱油规律与剩余油形成机理研究。取得的主要成果如下：.（1）形成了一套系统的缝洞型油藏两相流动实验技术和方法。设计和制作了缝洞型油藏系列物理模型，涉及裂缝介质、缝洞介质和离散缝洞模型，结合可视化技术、数据自动控制与采集技术和传感器测量技术，建立了缝洞型介质两相流、水驱油以及气驱油过程实验装置与实验系统。.（2）提出了裂缝介质两相流特征、流型，并采用Lockhart and Martinelli等方法，建立了基于流型的裂缝介质两相流均相预测模型；根据不同开度裂缝水驱油和气驱油实验特征，提出采用窜逸系数表征裂缝窜逸的严重程度，并建立了以裂缝开度与注入速度为自变量的裂缝介质水、气窜逸界限预测模型。.（3）明确了离散缝洞型介质水驱油、气驱油特征及其影响因素，基于修正的Dykstra-Parsons方法建立了底水驱替动态预测模型；考虑毛细管数、溶洞数量、流体粘度等因素，通过开展缝洞型介质油-气两相流实验，提出缝洞型介质两相流特征和流型，计算得到缝洞介质模型油-气两相流均相模型。.（4）以塔河油田实际井组地质模型为基础，建立了多缝多洞组合的缝洞型油藏二维剖面物理模型，明确了剩余油形成过程及赋存状态，并分析了溶洞充填、裂缝发育、注气速度、底水强度、注采层位等因素对剩余油形成的影响。.（5）项目开展以来，共发表期刊论文8篇和SPE会议论文1篇，其中SCI论文2篇，EI论文1篇，中文核心期刊论文6篇；授权发明专利2项，申请发明专利2项；获得校级科研奖励1项。