聚合物驱油层吸水剖面变化规律

统计分析大庆油田聚合物驱工业区块油层吸水剖面资料发现，绝大多数井中、低渗透层在注入聚合物溶液体积达0．08～0．2PV时吸水剖面发生返转，低渗透层吸水剖面返转时机先于中渗透层，且在整个聚驱过程中高渗透层仍保持最高的吸水量，对改善油层开发效果不利。数值模拟研究表明：层间渗透率级差及有效厚度比越大、注入聚合物分子量越小，聚合物溶液对低渗透层吸水能力的调整效果越弱；地层产能系数级差是影响吸水剖面返转时机和返转周期的主要因素。根据研究结果，提出：在聚合物驱层系组合时，应避免层间产能系数级差过大，分层注聚合物、优化聚合物分子量及段塞组合方式、注聚合物前深度调剖等措施可改善聚合物驱油效果。图10表2参13

Water injection profile variation of oil layers under polymer flooding

Statistical analysis in Daqing Oilfield indicates that the water injection profiles of low-permeability reservoirs retrograde when the injected polymer volume amounts to 0.08-0.2PV in most wells, and the retrograde time is earlier than that of mid-permeability reservoirs, and high-permeability reservoirs remain highest injectivity during the whole polymer flooding, which is unfavorable for improving the development results. Simulation shows that the bigger the reservoir permeability contrast and the effective thickness ratio of reservoirs, and the smaller the molecular weight of injected polymers, the poorer the adjustment results of polymer solution to the water absorbing capacity of low-permeability reservoirs; the reservoir productivity factor contrast is the main factor affecting the retrograde time and retrograde period of the water injection profile. The following measures are proposed to improve the results of polymer flooding: avoiding big reservoir productivity factor contrast in the combination of strata; separate polymer injection; optimizing the molecular weight of injected polymers and the combination of injected polymer slugs; and depth profile control before injecting polymers etc.