低渗透油藏自发生成中相微乳液洗油体系*

Spontaneous Formation of Middle-phase Microemulsion Oil Washing System in Low Permeability Reservoir

梁玉凯 于晓聪 袁 辉 阚长宾 陶世林 马 丁

LIANG Yukai YU Xiaocong YUAN Hui KAN Changbin TAO Shilin MA Ding

针对低渗透油藏作业、洗井过程中，储层流体返吐至井筒易导致启注压力升高的难题，通过室内实验优选 出一种快速自发生成的中相微乳液。考察了中相微乳液体系受地层水混入的影响及自发生成中相微乳液的洗 油效率和降压增注效果，并基于注水参数及微乳液“鱼状”相图特征，设计了自发生成中相微乳液的注入工艺。 结果表明，中相微乳液的组成为：1%～8%复配表面活性剂（非离子型表面活性剂、阴离子型表面活性剂质量比 为3∶1）、1.5%～3.5% C5醇和3.5% KCl水溶液。该体系形成中相微乳液的时间为15～30 min。当地层水混入量低 于50%时，中相微乳液增溶能力及中相微乳液中油和水的低界面张力性能不受影响。自发生成中相微乳液的洗油 效率大于99%。岩心驱替实验中，自发生成中相微乳液可使水驱驱替压差降低50.0%，降压效果显著。按设计的自发 生成中相微乳液的最小注入参数计算，可使半径为3.0 m的储层均得到清洗，达到降压增注的目的。

Injection pressure rises abruptly after well washing in low permeability reservoirs，due to back flow of fluids from formation to wellbore. Aiming at this problem，a novel system of middle-phase microemulsion generated spontaneously was developed. The influence of formation water on middle-phase microemulsion system was investigated. The efficiency of displacement efficiency and the effect of decreasing pressure and increasing injection by middle-phase microemulsion generated spontaneously were also studied. Based on the parameters of water injection and the fishlike phase diagram of microemulsion，the injection process of the middle-phase microemulsion was designed. The results showed that the formula of middle-phase microemulsion was obtained as follows：1%—8% compound surfactant（3∶1 mass ratio of nonionic surfactant to anionic surfactant）， 1.5%—3.5% C5 alcohol and 3.5% KCl aqueous solution. The middle-phase microemulsion could generate in 15—30 min. When the proportion of formation water was less than 50% in the mixture of formation water and injected agent，the effect of formation water on the solubilizing ability and low interfacial tension of oil and water in meddle-phase microemulsion was negligible. The displacement efficiency of middle-phase microemulsion was more than 99%. In the core displacement experiment，the system could reduce the water injection pressure difference by 50% ，and the effect was remarkable. According to the minimum injection parameters of middle-phase microemulsion by calculation，the near-well region as far as 3.0 m in radial direction could be cleaned. The purpose of decreasing pressure and increasing injection would be achieved.

10.19346/j.cnki.1000-4092.2021.04.020