大庆油田三类油层弱碱三元复合驱表面活性剂浓度优化

Surfactant concentration optimization of weak alkali ASP flooding system for ClassⅢreservoirs in Daqing Oilfield

大庆油田三类油层储层发育差,具有渗透率低、孔喉尺寸小、黏土含量高等特征,目前处于化学驱现场试验阶段。为了明确储层对注入化学剂吸附损耗的影响,保证化学驱开发效果,通过开展天然油砂条件下弱碱三元复合体系静态吸附实验,对比表面活性剂、碱、聚合物在三类油层与二类油层条件下的吸附损耗,利用室内物理模拟实验与数值模拟技术评价不同表面活性剂浓度对弱碱三元复合驱技术经济效果的影响,优化体系浓度并应用于现场。结果表明:三类油层对于表面活性剂的3次吸附损失为52.1%,比二类油层高17百分点;对于碱和聚合物的吸附量与二类油层相近;优化出三类油层弱碱复合驱体系中主段塞表面活性剂质量分数为0.35%、碱质量分数为1.2%,副段塞表面活性剂质量分数为0.20%~0.25%、碱质量分数为1.0%;NW区弱碱复合驱现场试验应用优化结果取得明显增油降水效果。研究成果对大庆油田三类油层推广化学驱具有指导意义。

ClassⅢreservoirs in Daqing Oilfield are poorly developed,with characteristics of low permeability,small pore throat size and high clay content.At present,they are in field test stage of chemical flooding development.In order to understand influence of reservoir on adsorption loss of injected chemical agents and ensure development effect of chemical flooding,static adsorption experiment of weak alkali ASP system in condition of natural oil sandstone is carried out to compare adsorption loss of surfactant,alkali and polymer in ClassⅢand ClassⅡreservoirs.Lab physical simulation experiment and numerical simulation technology are used to evaluate influence of different surfactant concentrations on economic effect of weak alkali ASP flooding technology,and the system concentration is optimized and applied in the field.The results show that adsorption loss of surfactant after 3 times of adsorption in ClassⅢreservoirs is 52.1%,which is 17 percentage points higher than that in ClassⅡreservoirs.The adsorption amount of alkali and polymer in ClassⅢis similar to that in ClassⅡreservoirs.Optimized weak alkali ASP flooding system for ClassⅢreservoirs has surfactant mass fraction of 0.35%and alkali mass fraction of 1.2%in main slug,and surfactant mass fraction of 0.20%~0.25%and alkali mass fraction of 1.0%in auxiliary slug.Field test application of the optimization result of weak alkali ASP flooding in NW block achieves obvious oil production increasing and water cut reducing effect.The research has guiding significance for promotion of chemical flooding for ClassⅢreservoirs in Daqing Oilfield.