低渗油藏纳米聚合物微球与低矿化度水复合深部调驱机理研究

The existence of relatively high-permeability layers is the main reason for water channeling in low-permeability reservoirs, which leads to large amounts of remaining oil at the late stage of reservoir development. Polymer spheres and low-salinity water are both good candidates for in-depth profile control and oil displacement. The former focuses on in-depth profile control and the latter stresses oil displacement. Therefore, the integration of the two techniques is expected to achieve both goals of in-depth profile control and oil displacement. However, the micromechanisms of the synergistic interaction of polymer spheres and low-salinity water have yet to be explored. This project studies the mechanisms and applicability of nano-polymer spheres assisted low-salinity waterflooding in low-permeability sandstone reservoirs. The main content of this research includes: characterization of the effects of nano-polymer spheres and low-salinity water injection on reservoir wettability using physicochemical parameters; modeling of the stress state of clay particles in unsaturated systems, analysis of the effects of saturation and wettability on particle attachment and detachment, and verification of critical criteria for particle detachment by microfluidics; simulation of nano-polymer spheres assisted low-salinity waterflooding by coreflooding experiments and Lattice Boltzmann Method. This research aims to investigate the optimum matching condition of nano-polymer spheres and fissures & pores, probe into the micromechanisms of nano-polymer spheres assisted low-salinity waterflooding, and establish a theoretical foundation for the further exploitation of remaining oil in low-permeability reservoirs.

低渗油藏中相对高渗层的存在是引起注入水窜逸的主要原因，导致油藏在注水开发后期仍然存在大量剩余油未被波及。聚合物微球和低矿化度水驱是油藏深部调驱的两种有效手段，前者侧重调剖，后者侧重驱油。因此，聚合物微球和低矿化度水的结合有望达到兼具调剖和驱油的双重效果，而其二者协同增效的微观机制尚待探索。本项目拟以低渗砂岩油藏为研究对象，对纳米聚合物微球与低矿化度水复合深部调驱机理及其适应性进行研究。具体内容包括：通过表面物理化学参数表征纳米微球和低矿化度水对储层润湿性的影响；建立油水两相非饱和体系下黏土颗粒微观受力模型，分析饱和度和润湿性对颗粒吸附/脱附的影响，并通过可视化实验进行验证；利用岩心驱替实验和格子玻尔兹曼方法模拟纳米微球与低矿化度水复合深部调驱的作用效果。本项目旨在探讨纳米微球与缝、隙结构的匹配条件，探究其与低矿化度水复合深部调驱的微观机理，为低渗油藏剩余油的进一步开发奠定理论基础。

低渗油藏中相对高渗层的存在是引起注入水窜逸的主要原因，导致油藏在注水开发后期仍然存在大量剩余油未被波及。聚合物微球和低矿化度水驱是油藏深部调驱的两种有效手段，前者侧重调剖，后者侧重驱油。因此，聚合物微球和低矿化度水的结合有望达到兼具调剖和驱油的双重效果，而其二者协同增效的微观机制尚待探索。. 以低渗砂岩油藏为研究对象，对纳米聚合物微球与低矿化度水复合深部调驱机理及其适应性进行研究。具体研究内容包括：通过表面物理化学参数表征纳米微球和低矿化度水对储层润湿性的影响；应用原子力显微镜测量不同条件下粘附力，分析温度和矿化度对颗粒吸附/脱附的影响；通过岩心驱替实验对纳米聚合物微球与低矿化度水复合调驱效果进行评价，揭示岩心驱油过程中不同尺寸孔隙中原油动用程度和驱油机理；建立低矿度水驱微粒运移数学模型和纳米聚合物微球深部运移数学模型。. 结果表明，改性纳米聚合物微球可以使油湿性固体表面变为亲水性润湿；钠离子有利于纳米颗粒将油湿性固体表面改变为水湿性；温度对改变岩石表面润湿性影响不大。粘附力随着盐度增加或温度升高而减小；基于XDLVO理论计能够更准确地解释在高盐度下的粘附力测量结果。微球能够有效封堵水窜通道，改变注入流体流动方向，使低矿化度水进入中小孔隙，提高波及效率和驱油效率。低矿化度水驱微粒运移数学模型能够准确地表征水驱前缘对颗粒脱落的影响以及岩心出口颗粒浓度随时间的变化。将纳米聚合物微球深部运移数学模型和岩心各部位压降实验数据进行拟合，进一步验证了微球在多孔介质中的深部运移特性及封堵性能。本项目研究证实了低矿化度水与纳米聚合物微球协同增效驱油提高低渗油藏采收率的潜力，并明确了纳米聚合物微球与低矿化度水复合深部调驱机理，为低渗油藏剩余油的进一步开发奠定理论基础。