注聚驱防砂井挡砂介质物理化学复合堵塞机制试验

针对孤东油田注聚驱防砂井液量降低严重并且绕丝筛管砾石充填防砂井的提液效果普遍低于树脂滤砂管独立筛管防砂的反常现象,首先通过砾石层特性评价试验研究地层砂对砾石层侵入及机械物理堵塞机制,得到砾石层堵塞与砾砂中值比、泥质含量、流体黏度、产量、生产时间以及聚合物的定性和定量关系。针对物理堵塞机制难以解释砾石充填和树脂滤砂管防砂堵塞现象的问题,开展普通石英砂与树脂涂敷砂的润湿性、沥青质吸附、聚合物及其衍生物吸附机制与规律试验对比,提出注聚驱防砂井的物理化学复合堵塞机制。研究表明:物理堵塞主要发生在投产早期,堵塞程度随着流体黏度、泥质含量、产量、聚合物含量、砾砂比(GSR)增加而趋于严重;与树脂涂敷砂相比,石英砂充填层表面强亲水,其对聚合物及其衍生物和胶质沥青质的表面吸附量远高于高渗滤涂敷砂,吸附量随着聚合物浓度增加以及石英砂粒径的减小而增大。在注聚驱条件下,原本高孔高渗的石英砂充填层复合堵塞后的渗透率反而远低于高渗滤砂管。

Experimental study on mechanical and chemical combined plugging mechanism of sand control media in heavy oil reservoirs with polymer flooding

During polymer flooding of heavy oil reservoirs in Gudong Oilfield, the well productivity decreased greatly in the early production stage after sand control measures were applied. It was observed that it is much more difficult for wells with wire-wrapped screen gravel-pack for sand control to achieve better performance than wells with resin-coated screen stand-alone method, which is inconsistent to the usual practice. In this study, series of experiments were firstly conducted to reveal the mechanisms of sand invading and plugging in the gravel packs. The influence of gravel-sand ratio (GSR), clay content, fluid viscosity, flow rate and production time on plugging rate in the presence of heavy oil and polymer were investigated. In order to investigate the chemical plugging mechanisms, the effects of wettability, asphaltene adsorption, polymer adsorption on clean quartz gravel and resin-coated gravel were then tested and analyzed. Based on the experiment results, a combined mechanical and chemical plugging mechanism was proposed to explain to the cumulated plugging phenomenon during polymer flooding. The experimental results indicated that, for the gravel packs with clean sands, mechanical plugging of the sand retention media takes place in the early stage of the production, and high GSR, fluid viscosity, clay content, production rate and polymer content tend to increase the plugging rate. In comparison with the resin-coated gravels, the clean quartz sand gravel is of higher water wettability and has high capacity to adsorb asphaltene and polymers, which was also verified by adsorption testing at different conditions. The polymer adsorption on the gravel surface increases with the polymer concentration and small gravel size. It is concluded that, during polymer flooding of heavy oil reservoirs, the reason for the permeability reduction of the clean sand packed gravel can be attributed the chemical plugging induced by polymer and heavy oil components.