压裂返排液化学分析及预处理工艺优化研究

Study on Chemical Analysis and Pretreatment Process Optimization of Fracturing Flowback Fluid

针对油田压裂开发中产生大量胍胶返排液难以处理、安全环保压力大的问题,对压裂返排液成分进行了研究,指出油田压裂返排液为中性或弱碱性,具有含油量较高且油水不易分离的特点。由于返排液的高矿化度,离子成分复杂,无机离子中以高价阳离子影响较大,故需对返排液预处理工艺和加药方案进行优化。实验结果表明:根据返排液中各类离子含量,添加适量的NaOH和Na_(2)CO_(3)复合体系,Na_(2)CO_(3)+NaOH添加量在2050~2400 mg·L^(-1)和500~600 mg·L^(-1)时处理效果最优,可以有效地去除钙、镁、铁离子,其中Ca^(2+)和总铁离子有较好的去除率,可达90%以上,Mg^(2+)去除率为73%,但Mg^(2+)去除后含量已符合标准要求,处理后满足现场使用要求。确定其处理工艺为“气浮除油-氧化破胶和阳离子去除-混凝脱稳-板框压滤-水质净化”联合工艺,SS去除率高达99.5%,COD去除率超过90%,处理后的水对再配压裂液性能影响降至最小,表明工艺效果较为突出。

Aiming at the problem that a large amount of guanidine gum backflow produced in oilfield fracturing development was difficult to treat and had great pressure on safety and environmental protection,the composition of fracturing flowback fluid was studied,and it was pointed out that fracturing flowback fluid was neutral or weakly alkaline,which had the characteristics of high oil content and difficult separation of oil and water.Due to the high salinity of the flowback liquid,the ion composition was complex,and high-valent cations had a greater impact on the inorganic ions,so it was necessary to pretreat the flowback liquid.The experimental results showed that according to the content of various ions in the flowback liquid,an appropriate amount of NaOH and Na_(2)CO_(3)composite system was added,and when the amount of Na_(2)CO_(3)+NaOH was 2050~2400 mg·L^(-1) and 500~600 mg·L^(-1),the best treatment effect was obtained,and calcium,magnesium,and iron ions were effectively removed.Among them,Ca^(2+)and total iron ions had a good removal rate,which was more than 90%,and the removal rate of Mg^(2+)was 73%,but after Mg^(2+)removal,the content met the standard requirements,and it met the requirements for on-site use after treatment.The treatment process was determined as follows:the combined process of"air flotation degreasing-oxidation gel breaking and cation removal-coagulation destabilization-plate and frame filter press-water purification",the SS removal rate was as high as 99.5%,and the COD removal rate exceeded 90%.The effect of the treated water on the performance of the reconstituted fracturing fluid was minimized,indicating that the process effect was more prominent.