中原油田注水水质改性技术

Injection Water Quality Adjustment for Reservoir Flooding at Zhongyuan Oil Fields

中原油田注入水水源以油田产出水为主,也使用洗井回水及清水。过去采用"除油—沉降—过滤"并加入杀菌剂、缓蚀剂、净水剂、阻垢剂的三段式水处理工艺,处理后水质不达标而且不稳定,沿注入系统流程不断恶化,特别是腐蚀性十分严重,其原因是该水富含游离CO2和HCO-3,形成了弱酸性缓冲溶液。据此提出了调整水中离子、改变水性的水处理方法:将油田产出污水和清水(或其他污水)混合,加入pH调节剂(石灰乳)和絮凝剂,经沉淀、过滤后加入水质稳定剂,得到水质合格并稳定的注入水。产生的污泥压榨脱水后制成含水50%的泥饼。该水处理工艺从1995年到1999年先后经过初步矿场试验和工业性试验,在中原油田9个污水站成功推广应用,处理后的注入水pH值8.0～8.5,腐蚀速率0.003～0.040mm/a,溶解氧、S-、悬浮物、含油、MF值、总铁、SRB、TGB、Fe细菌数等水质项目均达到注入水行业标准且稳定性良好,在地面系统和地层内不结垢。产生污泥量大及污泥利用问题正在解决中。图2表2参4。

The main water source for reservoir flooding at Zhongyuan oil fields is produced water with recycled well washing water and fresh water as supplementary ones. A threestage (deoiling-sedimentationfiltration) water treating technology with bactericide, corrosion and scale inhibitors, and water puring agent added was applied and the quality of the treated water was not satisfactory to the standard requirements and unstable, getting worse and worse along the injection system, and its corrosivity became severe particularly. This results from rich free CO2 and ion HCO-3 which make up the water into a weakly acidic buffer solution. A method of water treatment adjusting ions in the water and changing water behavior is suggested and developed: the oilfield produced water be mixed with fresh water (or other wastewater), pH value adjuster (lime cream), and a flocculant, sedimentated, filtraled and treated by a water quality stabilizer to give a qualified and stable injection water. The sludge formed is compressed to give cake of 50% water content. From 1995 to 1999 the water quality adjusting technology went through pilot and industrial field tests and put into field use successfully in 9 water treating plants of Zhongyan oil fields: for the treated injection waters pH value 8.0-8.5; corrosion rate 0.003-0.040 mm/a; water quality very stable and meets to trade standard in contents of O2, S-, SS, oil, ΣFe, MF value, and bacteria population of SRB, TGB, and Fe bacteria; the water is not scaling in surface systems and in substratal formations. The problems of sludge creation in large amount and its utilization are under study.