纳滤法处理富含SO_4^(2–)油田注入水的防垢阻垢作用

The Antiscale Effect of Nanofiltration Membrane Treatment Technology for Oilfield Injection Water Containing High Concentration of SO_4^(2-)

针对姬塬油田注入水富含SO_4^(2–),在注水过程中易与高矿化度地层水中的Ba^(2+)、Sr2+形成难溶性硫酸钡锶垢的问题,采用纳滤膜脱除SO_4^(2–)成垢离子防止垢的生成。研究了源水经纳滤处理前后与地层水的配伍性及其对岩心的损害,考察了该技术在姬塬油田的现场应用效果。研究结果表明,采用纳滤膜处理技术可有效降低注入水中的SO_4^(2–)含量,防止结垢产生的地层损害。经过纳滤处理后,源水中SO_4^(2–)含量由2499.88 mg/L降至428.03 mg/L,SO_4^(2–)脱除率达到82.9%。纳滤水与地层水以不同比例混合后的结垢量均小于源水与地层水混合的结垢量,纳滤水的阻垢率为70.4%数74.2%;纳滤处理前后,源水对岩心的伤害率分别为46.13%和1.47%,纳滤水可有效抑制对岩心的损害。现场试验表明,注入水经纳滤脱SO_4^(2–)工艺处理后,姬W注水站注入水中的硫酸根减少80%以上;试验区36口井注水压力平均降低1.41 MPa,11口吸水剖面测试井剖面厚度平均增加1.35 m,显示出良好的处理效果。

The injection water was rich in SO_4^（2-） in Jiyuan oilfield,which was easy to form insoluble BaSO_4 or SrSO_4 with Ba^（2＋）and Sr^（2＋）in high salinity formation water during injection process. So the nanofiltration membrane was used to remove SO_4^（2-） and prevent scale formation. The compatibility of source water and formation water as well as the damage to the core were analyzed before and after nanofiltration treatment,and the application effect of this technology was examined in Jiyuan oilfield. The results showed that nanofiltration membrane treatment technology could effectively reduce the content of SO_4^（2-） in injection water and prevent the formation damage caused by scale. After nanofiltration process,the content of SO_4^（2-）decreased from 2499.88 mg/L to 428.03 mg /L in source water,and the removal rate of SO_4^（2-） reached 82.9%. Scaling quantity of nanofiltration water and formation water with different mixing ratio was less than that of source water and formation water mixed,and the inhibition rate of nanofiltration water was 70.4% —74.2%. The core damage rate of source water before and after nanofiltration treatment was 46.13% and 1.47%respectively. Nanofiltration water could effectively suppress the damage to the core. Field test results showed that after nanofiltration treatment,the content of SO_4^（2-）in injection water at Ji W station reduced more than 80%,the average injection pressure of 36 wells in test area reduced 1.41 MPa,the profile thickness of 11 injection profile test wells increased by an average of 1.35 m,showing good effect.