二氧化碳驱采出井缓蚀剂筛选与评价流程研究

Study on screening and evaluation process of inhibitors for carbon dioxide flooding wells

关键词:  CO₂驱  采出井  缓蚀剂  筛选  评价流程

Key words:  CO₂ flooding  producing well  corrosion inhibitor  screening  evaluation process

摘要:

添加缓蚀剂是油气田控制井筒腐蚀的主要手段,如何筛选出合适的缓蚀剂是预防井筒腐蚀的关键。以某油田CO₂驱采出井(井筒内温度60~120 ℃,CO₂分压为0.2 MPa)缓蚀剂筛选评价为例,首先利用配伍性试验初步评价缓蚀剂的理化性能,然后采用电化学方法进一步筛选出缓蚀率大于90%的缓蚀剂,最后利用高温高压釜模拟现场工况(90 ℃和120 ℃,CO₂分压为0.2 MPa),对拟选用的缓蚀剂进行腐蚀失重评价实验,并辅以SEM分析缓蚀剂的防腐效果。实验结果表明:7种待评价缓蚀剂中,4种缓蚀剂可与现场采出液良好配伍；缓蚀剂质量浓度为200 mg/L时,有两种缓蚀剂在常压下的缓蚀率大于90%；在加注浓度为1 mol/L、模拟实际生产工况下,筛选出的最优缓蚀剂可将D级杆和N80的腐蚀速率降至油田腐蚀控制指标0.076 mm/a以内。研究表明,先以配伍性评价,后通过电化学评价进一步筛选,最后采用高温高压釜模拟工况测试验证,可以快速筛选出适用于CO₂驱采油井的缓蚀剂。 

Abstract:

Adding inhibitors is the main method to control wellbore corrosion of oil and gas fields, and the key of prevent wellbore corrosion is how to screen suitable inhibitors. The screening and evaluating of inhibitors for CO₂ driving well of an oilfield were taken as an example in this paper, and the temperature of wellbore was 60-120 ℃ and CO₂ partial pressure was 0.2 MPa. Firstly, the physical and chemical properties of the inhibitors were evaluated by compatibility experiment. Secondly, the corrosion inhibitors with inhibition efficiency greater than 90% were screened out by electrochemical method. Finally, the working conditions was simulated by using HTHP autoclave (the temperature were 90 ℃ and 120 ℃, and CO₂ partial pressure was 0.2 MPa), then the inhibitors were evaluated by experiment of corrosion weight loss and by SEM analysis for the antiseptic effect. Experimental results show that there are four in seven inhibitors have the good compatibility of inhibitors and produced liquid, when the inhibitor concentration is 200 mg/L, the inhibition efficiencies of two inhibitors are more than 90% at atmospheric pressure. Under the filler concentration of 1 mol/L and simulating the actual production conditions, the optimum inhibitor can reduce the corrosion rate of D rod and N80 steel within 0.076 mm/a up to the corrosion control index of oilfield. The study shows that the inhibitors which are suitable for CO₂ driving wellbore can be screened and evaluated rapidly by the compatibility experiment, the screening of electrochemical test, and the verification of simulating wording conditions by using HTHP autoclave.