大天池气田井下油管损伤分析

Damages of downhole tubing in Datianchi Gas Field

为针对性地解决大天池气田井下油管在服役过程中的损伤问题,通过腐蚀检测、修井起出油管观察,对生产过程中的油管损伤进行实时分析并提供对策。结果表明:(1)产出流体的强腐蚀性及流体中杂质极易导致油(套)管腐蚀,使其承压能力不足,进而变形挤压油管,是生产中后期气井井下油管损伤的因素之一;(2)腐蚀过程中产生的垢物附着在油管内外壁,将产生持续的垢下腐蚀,导致井下油管穿孔、断落。据此,提出4条井下防护措施:(1)选取合适的油套管材质和油管结构,提高管串的抗损伤能力;(2)尽量排完入井液,避免产生井下腐蚀条件;(3)合理配产,尽量降低冲蚀影响;(4)定期检测井下管串,及时调整防护方案或更换油管。

In order to prevent in-service downhole tubing from damages, the tubing damages in Datianchi Gas Field were analyzed by detecting the corrosion and observing the tubing tripped out during workover. Results show that（1） for gas wells, during their middle to late development stages, two factors leading to these damages are individually the strong corrosivity of produced fluid and the impurities in fluids easily causing tubing/casing corrosion, which may deteriorate tubing/casing bearing capacity and consequently lead to casing deformation enough to extrude the tubing; and（2） the scales generated from corrosion attaching to the inner and outer of tubing walls, result in cortinuous subscale corrosion, and the downhole tubing is perforated and broken due to continuous corrosion. In addition, four countermeasures against downhole damages are made, containing, to select suitable tubing and casing materials or tubing structures to improve an anti-damage capacity of pipe strings, to drain the fluid as much as possible to avoid creating downhole corrosion conditions, to arrange production proration rationally to minimize erosional impact, and to check downhole pipe strings regularly and adjust protective schemes or replace tubing in time.