疏松砂岩油藏进入高含水期后,由于注入水的冲刷和油层本身的非均质性,储层孔隙结构发生了变化,注入水主要沿各沉积单元的高渗透层突进,导致水洗厚度基本不变,出现了严重的“低效、无效循环”现象。针对大庆油田北二东西块地质特点和长期注水开发历程,分析了低效、无效循环在生产过程中所呈现出的特征,总结出高含水后期油藏极易形成低效、无效循环的三个部位,即:垂向高渗透层、厚油层底部和注入水主流线。在此基础上,运用数值模拟方法进行了研究,给出了相应的形成条件,为高含水后期制定出了切实可行的油田开发界限,并为同类油藏有效预防和治理注入水低效、无效循环提供了直接依据。
In unconsolidated sandstone reservoir with high water cut, pore structures have been changed due to the erosion of injected water and formation heterogeneity. The injected water flow along the high permeability zones which cause the water flushed thickness unchanged and the low and useless circling phenomena occurred. According to the geological characteristics and the long time of water injection development of Beierdongxi block in Daqing Ooilfield, the low and useless efficiency circling occurring during production was analyzed. Three places in the reservoir where the low and useless efficiency circling occurred at reservoirs with the high water cut, including formation with high vertical permeability, bottom layer of the formation with thick payzone and the main streamline of injected water, were summarized. Thereafter, the numerical simulation was used and the corresponding forming conditions were provided. The results can be used to construct the applicable development limits for reservoirs and can also provide the direct basis for similar reservoirs in preventing and controlling the low and useless circling.