Analysis of Oil Well Blockage in K Oilfield in Kazakhstan and Blockage Removal Techniques
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摘要: K油田井下油管、套管出现了较为严重的作业后堵塞问题,严重影响了油井正常生产。针对这一问题,鉴定了堵塞物类型并研制了一种螯合型高效解堵剂。首先,对K油田的储层特征进行了全面的分析,了解其潜在的油井堵塞可能,得出结垢和CO2腐蚀剥落铁锈的可能堵塞原因。然后,根据XRF和XRD等大型仪器分析结果,确定了堵塞物的主体为氧化铁并含有少量石盐。最后,通过多种酸液体系的溶解实验,进一步确认了堵塞物类型,并优选出螯合剂与氢氟酸组合的解堵液配方体系和与之适应的缓蚀剂体系,同时使用现场井筒堵塞物样品对其进行了溶解验证实验。结果表明,该螯合型解堵液体系能够耐受120℃的高温,对油套管的N80钢片无溶蚀作用,而2 h内对堵塞物锈块样品有着高达82%的溶蚀率,达到既能保护油套管而又能溶蚀堵塞物的目的,显示出良好的解堵效率。该解堵液体系,加入KMS-Z缓蚀剂后,腐蚀速率大幅降低,低至8.91 g/(m2×h),可超过行业一级标准。与之相比,土酸体系虽然具有良好的溶解能力,但腐蚀速率始终无法得到有效控制,这可能与铁锈溶解后三价铁的高氧化性有关。Abstract: Blockage of tubing and casing was found in thedown hole of K oilfield, which seriously affected the production job. The type of the blockage was identified and a high efficiency chelating blockage removing agent was developed to addressthe problem. After identifying the composition of the blockage, the reservoir characteristics of the K oilfield were first analyzed toascertain the potential reasons of well blocking. It was found that scales and the peeling iron rust by CO2 corrosion were the possiblereasons of well blocking. Then, using XRF and XRD instrument, the main components of the blockage was determined, and they are ferricoxide and small amount of rock salts. Finally, by dissolving the blockage in various acid solutions, the type of the blockage wasfurther confirmed. A blockage removing fluid, made up of an optimized chelating agent, hydrofluoric acid and a corrosion inhibitorfluid, were then developed. It was found that theblockage removing fluid works well at 120℃ and has no harm to the N80 coupon. The dissolved ratio of the blockageis 82% in 2 h.This blockage fluid cannot only protect tubing/casing strings but also dissolve the blockage, and it show excellent blockage removing abilities. After adding a corrosion inhibitor KMS-Z, its corrosion rate reduces to 8.91 g/(m2·s), which exceeding the Class 1 of corrosionindustrial standard requirement. On the other hand, although mud acid have good dissolving ability to the blockage, it is unable to control corrosion rate. Failure of corrosion protection in mud acid maybe come from the strong oxidizing ability of the ferric ions.
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Key words:
- K Oilfield /
- Blockage /
- Blockage removing agent /
- Chelating agent Iron rust /
- Kazakhstan
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