注水中悬浮颗粒堵塞储层的影响因素分析

 注入水中悬浮颗粒能够严重堵塞油藏储层, 造成渗透率下降, 导致注水难、采油难。开展悬浮颗粒对储层伤害规律的研究, 对提高油田注水效果有着重要的指导作用。以5 种不同粒径的悬浮颗粒分别在3 种不同浓度溶液条件下, 对天然岩心进行室内流动实验。将粒径与喉道直径之比定义为匹配度, 流出液浓度与注入液浓度之比定义为相对浓度。结果表明:在岩心平均喉道直径0.94 μm、水测渗透率0.137×10^-3～0.235×10^-3 μm²条件下, 注入悬浮颗粒溶液后, 渗透率变小, 产生了堵塞。其中当匹配度小于0.777 时, 相对浓度大于0, 即部分颗粒能够贯穿岩心, 发生贯穿性堵塞;当匹配度大于0.777 时, 相对浓度为0, 即颗粒无法贯穿岩心, 发生浅部堵塞;在匹配度接近0.777 时, 为由贯穿性堵塞向浅部堵塞过渡阶段, 堵塞最严重。注入量与堵塞程度有较好的线性关系。建议油田在达到配注量的同时, 尽量减小注入水悬浮颗粒浓度, 保证悬浮颗粒粒径范围集中且匹配度远离临界值。

Influencing Factors of Reservoir Plugging Caused by Suspended Particles in Injected Water

Suspended particles in injected water can seriously plug the reservoir, which makes it hard for the water to be injected and the oil to be produced. In order to solve this problem, the plugging of a reservoir caused by suspended particles should be studied. In this paper, a core plugging experiment is designed, where 3 sizes and 5 concentrations of suspended particles are considered. The ratio of the diameter of the suspended particle to the throat diameter is defined as the compatibility. The ratio of the effluent concentration to the injection concentration is defined as the relative concentration. It is shown that when the throat diameter of the core is 0.94 μm and the water permeability of the core is 0.137～0.235×10^-3 μm², the permeability decreases and the plugging occurs after suspended particles are injected. When the particle compatibility<0.777, the relative concentration>0, a part of suspended particles can go through the core, the form of plugging is penetrable; when the particle compatibility>0.777, the relative concentration is 0, the suspended particles can not go through the core, the form of plugging is a shallow plugging; The particle compatibility 0.777 is the critical value from penetrable plugging to shallow plugging. Under an appropriate particle compatibility value, the pore volume and the plugging degree have a good linear relationship. It is suggested that the concentration should be low, the particle size should be in a limited range and the particle compatibility should be far below the critical value.