The Effect of Corrosion in Coiled Tubing and Its Prevention

摘要

Unpredictable coiled tubing(CT)service life is not acceptrnable in the CT industry and is not tolerated by the customer．rnExperience shows that service life becomes unpredictablernwithout adequate tubing maintenance programs that includerncorrosion prevention.Therefore，monitoring and maximizingrnC7 service life requires effective corrosion Control on bothrninside and outside C7 surfaces from the time the tubing stringrnis milled until it is retired．Corrosive degradation of CT canrnresult from contact with the atmospherice nvironment，pumpedrnfluids，and production fluids.Corrosion，especially localizedrncorrosion．Must be prevented because it can greatly affectrntubing life by initiating premature fatigue cracking and growthrnduring cycling.Additionally，corrosion can reduce usablerntubing strength and pressure integrity.rn This paper discusses effective preservation and inhibitionrnprograms instituted at the tubing mill,service centers,and inrnthe field.In addition，electrochemical corrosion-rate data forrnas-milled and cycled CT is presented．Linear-polarizationrnresistance and Tafel-curve generation were used to deriverngeneral corrosion-rate data for new and cycled CT-90 and C7-rn100 in various comlilon oilfield fluids,including a stimulationrnfluid.These tests suggest that CT corrosion tendency is notrnsignificantly accelerated as a result of cycling，except at highrntemperatures.Additionally，the paper presents high-pressurernfatigue data from testS performed on CT-90．Comparing fatiguernlifc in water and in inhibited 15％hydrOChloric acid(HCl).