低矿化度水与表面活性剂混注提高稠油采收率机理

Hybrid low salinity water and surfactant process for enhancing heavy oil recovery

针对低矿化度水与表面活性剂混注工艺提高原油采收率机理不清的问题,采用墨西哥东南部砂岩油藏储集层岩心和稠油样品,开展了加入表面活性剂和未加入表面活性剂条件下的低矿化度水岩心驱替实验,并结合层析分析方法,研究驱替过程中岩心内部的变化。结果显示,低矿化度水和表面活性剂混注工艺能够提高采收率,实验中低矿化度水驱与混注工艺提高岩心采收率11.4个百分点。低矿化度水驱使得岩心中产生多种现象,例如润湿性改变、pH值变化、离子交换、矿物溶解、微粒运移和原油组分变化等。在表面活性剂驱替过程中,界面张力降低和润湿性改变是提高采收率的主要机理。以往研究认为低矿化度水驱提高原油采收率需要储集层中存在高岭石或原油为高酸值原油,但驱替实验结果表明这两点并非必要条件。

Combining low salinity water(LSW)with surfactants has an enormous potential for enhancing oil recovery processes.However,there is no consensus about the mechanisms involved,in addition to the fact that several studies have been conducted in model systems,while experiments with rocks and reservoir fluids are scarce.This study presents a core-flooding experiment of LSW injection,with and without surfactant,using the core and heavy oil samples obtained from a sandstone reservoir in southeastern Mexico.The effluents and the crude oil obtained at each stage were analyzed.The study was complemented by tomographic analysis.The results revealed that LSW injection and hybrid process with surfactants obtained an increase of 11.4 percentage points in recovery factor.Various phenomena were caused by LSW flooding,such as changes in wettability and pH,ion exchange,mineral dissolution,detachment of fines and modification of the hydrocarbon profile.In the surfactant flooding,the reduction of interfacial tension and alteration of wettability were the main mechanisms involved.The findings of this work also showed that the conditions believed to be necessary for enhanced oil recovery with LSW,such as the presence of kaolinite or high acid number oil,are not relevant.