砂岩油藏聚合物堵塞机理及解堵方法研究

针对砂岩油藏聚合物驱过程中聚合物堵塞严重的问题,利用长填砂管多点测压驱替实验和油藏工程方法确定聚合物堵塞半径,利用电镜扫描、CT扫描、核磁共振等手段研究聚合物堵塞机理。结果表明:聚合物堵塞主要发生在靠近填砂管注入端0～1/4处;高渗岩心表面吸附有大量聚合物,聚合物堵塞主要是由吸附引起的,低渗岩心孔径小,孔喉处机械捕集量大,聚合物堵塞主要是由机械捕集引起的;相比于聚合物驱前,聚合物驱后的岩心孔喉平均半径和平均喉道配位数减少,平均孔喉半径由42.2 μm降至39.9 μm,平均喉道配位数由3.36降至3.19。基于堵塞半径和堵塞位置的研究结果,进行了解堵现场试验,解堵后的视吸水指数为解堵前的10.5倍,达到了配注要求。该研究结果可为砂岩油藏聚合物堵塞机理研究和聚合物驱现场试验提供一定的理论指导。

Study on Polymer Plugging Mechanism and Plug Removal Method in Sandstone Reservoirs

In order to solve the problem of severe polymer plugging in polymer flooding process in sandstone reservoirs, the polymer plugging radius was determined by the displacement experiment with multi-point pressure measurement of long sand-packed pipe and the reservoir engineering method, and the polymer plugging mechanism was studied by scanning electron microscopy, CT scanning, nuclear magnetic resonance and other methods. The results showed that, polymer plugging mainly occurred at 0-1/4 near the injection end of the sand-packed pipe; a large amount of polymer was adsorbed on the surface of the high-permeability cores, and polymer plugging was mainly caused by adsorption; the pore size of the low-permeability core was small and a great amount of polymer was mechanically captured at the pore throat, and polymer plugging was mainly caused by mechanical capture; compared with that before polymer flooding, the average pore throat radius and average throat coordination number of core after polymer flooding were reduced, with the average pore throat radius reduced from 42.2 μm to 39.9 μm and the average throat coordination number reduced from 3.36 to 3.19. Based on the study results of plugging radius and location, the field test of plug removal was implemented. The apparent water injectivity index after plug removal was 10.5 times that before plug removal, meeting the injection requirements. The results of the study provide theoretical guidance for studying the polymer plugging mechanism in sandstone reservoirs and the field test of polymer flooding.