An Experimental Study on the Plugging Mechanisms of Sand-Preventing Medium in the Near-Well Zone of Sand Control Wells in Heterogeneous Polymer-Flooding Reservoirs

In light of the plugging problem in oilfield development using the heterogeneous polymer flooding, a simulation experiment to evaluate the plugging due to polymer plug in the sand-preventing medium in the near-well zone was carried out. It used a experimental simulation device of medium plugging of heterogeneous composite flooding. In the experiment, formation sand with grain sized averaging a diameter of 0.15 mm and gravel with a diameter range of 0.6–1.2 mm were used. In conjunction, three types of fluids, including clear water, a tackifying base fluid and a compound fluid contained PPG and polymer material were used. Further, the polymer plug samples in the sand control wells were used, respectively. The results showed that while it was in the gravel packing layer, the plug tended to migrate along the high permeability zone. Carried by fluid shear, the small viscous balls would be peeled off from the plug and then squeezed into the pores and throats in the deep gravel layer. These small, viscous balls impeded the migration of formation sand and intensified the degree of plugging degree in the gravel layer, which was positively related to the plug content. The outcome was a decrease in overall permeability. The results showed that the plugging in the near-well zone of gravel packed sand control wells treated by heterogeneous polymer flooding was a result of physical and chemical compound plugging of polymer dope, plug and solid particles. Early de-plugging measures should be taken to prevent plugging degree aggravation.