海上油田水质处理及其对驱油剂性能影响研究

OFFSHORE OILFIELD WATER TREATMENT AND ITS IMPACT ON THE PERFORMANCE OF OIL DISPLACEMENT AGENT

渤海LD5-2油田注入水中Ca2+和Mg2+浓度较高,致使聚合物溶液增黏性变差,进而影响驱油剂的调驱性能。针对海上油田特征和注入水水质特点,笔者开展了水处理方法筛选及其水处理效果评价,在此基础上进行了水质对驱油剂增黏性、流动特性、分子线团尺寸、分子构型影响研究。结果表明,LD5-2油田注入水中Ca2+和Mg2+浓度含量超过900mg/L,对聚合物溶液和Cr3+聚合物凝胶性能造成严重不利影响。水处理结果表明,"氢氧化钠-碳酸钠"加药法技术效果和经济效益较好,适用于海上油田水处理。与注入水相比较,软化水聚合物溶液和Cr3+聚合物凝胶黏度较高,分子线团尺寸较大,分子构型趋向伸展,阻力系数和残余阻力系数较大。与钾钠离子相比较,钙镁离子使聚合物分子链更倾向于卷曲构象,黏度降低幅度更大。

Ca2+ and Mg2+ concentration of Bohai LD5-2 oilfield injection water was higher,this resulted in increased polymer solution viscosity variation,thereby affected the performance of displacement agent.In view of the features of offshore oil platform and the water quality of injection water,the screening water treatment method and evaluating treatment effect were carried out by using device detection and theoretical analysis method,and the impact of water quality on shear resistance,temperature resistance,flow characteristics,molecular coil size,molecular configuration of displacement agent was studied.The results showed that,when Ca2+ and Mg2+ concentrations in LD5-2 oilfield injection water were above 900mg/L,it had adverse effect on the properties of polymer solution and Cr3+ polymer gel.Water treatment results showed that dosing method 'sodium hydroxide-sodium carbonate' could make the content of calcium and magnesium lower in water treatment,and obtained better technical effectiveness and economic benefits for offshore oilfield water treatment.Compared with the injection water,viscosity of polymer solution and Cr3+ polymer gel prepared by softened water was higher,molecular coil size was larger,molecular structure tend to stretch,resistance coefficient and residual resistance coefficient were larger.Compared with K+ and Na+,calcium and magnesium ions made the polymer chains tend to coil conformation,the decrease of viscosity was speedier.