The Study On Blockage Reason And Treatment Methods Of Water Injection Well In Changbei Gas Field

With the deepening of the development of ChangBei gas field, it has been into stable period, the gas production increased while the water production increased, the water back to reservior directly through treatment of gas treatment plant of ChangBei. Beause the quality of rejection water is complex, the contents of Condensate oil and suspended solids is very high, which resulted in reinjection wells blockage and poorer formation permeability, injection pressure increased rapidly and small amount of injection even can not be injected. Therefore, the execution of HC1Acidizing has been done on-site many times, the effect is good in the beginning, the amount of injection has been increased, but with the execution times increasing, the effect has been worse, which impacted the reinjection process severely.In the paper, based on the many researches on-site, through various laboratory Analysis and Evaluation, Firstly, the Characteristics of the composition properties of water was analyzed and Effect of the water treatment process was evaluated; Secondly, the Characteristics of the composition properties of water and sediments was analyzed, the main reason of reinjection wells blockage wa founded; Thirdly, through various kind of acid soluble experiments, Acidizing system suitable for water reinjection wells of ChangBei was determined; At last, according to the quality of water reinjection, modification scheme of water treatment technique was proposed, which reduced harm of reinjection water to wells.The result shows that:(1) the Composition properties of reinjected water and water contain oil of ChangBei gas field are the same, are all subacidity (average pH is6.5), Ion content are stable relatively, but the contents of emulsible oil and Suspended solids in the water are high with large range of variation, which increased the difficulty of pretreatment of water;(2) The water treatment techniques currently used in ChangBei gas field are not suitable for the quality of water contain oil, which results in the effect of equipment is not good, the contents of emulsible oil (M=1013.54mg/L)and Suspended solids(M=248mg/L) in the water after treatment in the high position with poor injection quality. If the water are reinjected, it would be result in blockage.(3) Through the Characteristics of the composition properties of water and sediments was analyzed comprehensively, the main factors of blockage are: emulsible oil, various solutionable organ and Suspended solids(main constitution is quartz sand)(4) The main factor of blockage is not HCl acidizing in ChangBei gas field.(5) Appropriate Well-off time and compounding of acidizing blockage remove is determined: ahead fluid:8%HCl, treatment fluid:3%ClO2+1.5%CI+0.15%WD-8+0.5%CF-5B+0.1%BE-2+0.3%KS-1, treatment fluid:10%HCl+4%HF+1.5%CI+0.15%WD-80.5%CF-5B+0.1%BE-2+0.3%KS-1, close the well for4hours (6) The proposal suitable for water treatment techniques is proposed, it is reduced the contents of emulsible oil and Suspended solids in the reinjected water, the harm they caused for.