早期注聚油田渗透率级差对剩余油分布规律影响研究

STUDY ON THE INFLUENCE OF PERMEABILITY DIFFERENCE ON REMAINING OIL DISTRI⁃BUTION IN EARLY POLYMER INJECTION FIELD

渤海X油田为早期注聚油藏,纵向厚度大,非均质性强,进入双高阶段后纵向各层剩余油分布异常复杂,稳油控水难度大。利用数值模拟方法,开展不同渗透率级差下早期注聚油田剩余油分布规律研究。结果表明:水驱阶段,随着渗透率级差增大,注入水会增加对模型中上部中高渗层的驱替程度,渗透率级差越大,增加幅度越大,模型顶部剩余油的富集程度越小,模型底部低渗层剩余油越富集;聚驱阶段,扩大在中高渗层的驱替程度,但对低渗层的驱替程度减弱。与水驱相比,模型上部剩余油的富集减小,模型下部剩余油的富集增加。渗透率级差主要影响模型下部低渗层剩余油富集,对于早期注聚油田,模型下部低渗层剩余油富集渗透率级差界限值为8。

Bohai X oilfield is an early polymer injection reservoir with large longitudinal thickness and strong heterogeneity.After entering the double-high stage,the water flooding situation of each vertical layer is complicated,and it is difficult to stabilize oil and control water.In this paper,numerical simulation method is used to study the influence of residual oil distri⁃bution in early polymer injection fields under different permeability levels.The results show that:in the water flooding stage,with the increase of permeability level difference,the injected water will increase the displacement degree of the middle and upper high permeability layer of the model.The larger the permeability level difference is,the greater the increase range is,the smaller the enrichment degree of the remaining oil at the top of the model,and the more concentrated the remaining oil in the low permeability layer at the bottom of the model.In polymer flooding stage,the degree of displacement in the middle and high permeability layer is enlarged,but the degree of displacement in the low permeability layer is weakened.Compared with water flooding,the enrichment of the remaining oil in the upper part of the model decreases,while the enrichment of the re⁃maining oil in the lower part of the model increases.Permeability grade difference mainly affects the enrichment of remaining oil in the lower low permeability layer of the model.For the early polymer injection oilfield,the threshold value of the enrich⁃ment permeability grade difference of remaining oil in the lower low permeability layer of the model is 8.