应用分步射孔改善油层动用不均匀现象研究

Improvement of Inhomogeneous Producing Degree for Polymer-Flooding Layers Applying Step Perforation

针对油藏非均质性严重,聚驱后低渗透层动用程度仍较低,厚油层内部剩余油仍大量存在,纵向动用不均匀的问题,提出了一种应用分步射孔改善聚驱油效果的方法,即在水驱结束后,对厚油层选择性射孔并水驱挖潜后再转注聚。应用室内物理三管并联驱油实验和理论公式,分析分步射孔聚合物驱油机理,并结合数值模拟,以北北块二区为目标,研究了分步射孔后聚驱对开发效果的影响。结果表明,采用大前置段塞、高相对分子质量、梯次降浓段塞组合,聚驱效果最好;分步射孔后注聚相较于不经过分步射孔直接注聚,低渗透层动用程度更大,驱油效果更好,最终采收率提高了1.28%。

A method which applies step perforation to improve the effect of polymer flooding is presented against the problems of poor producing degree of low permeability, remaining oil in the inner thick oil layer abounds, and uneven vertical producing degree. After water flooding, the thick layers are perforated selectively followed by water flooding potential tapping, and the polymer flooding is performed ultimately. By carrying out laboratory physical oil displacement experiment of three-tube parallel cores and applying theoretical formulas, reasonable polymer injection parameters are determined and the impacts of polymer flooding after step perforation on development effectiveness are also studied. The results showed that the better effect of polymer flooding was obtained by using big pre-slug, high molecular weight polymer, and echelon descending concentration slug combinations. And projects which had adopted step perforation showed a bigger producing degree on low permeability layers and a better effectiveness on polymer flooding compared to the ones not adopted step perforation. The ultimate recovery was increased by 1.28%.