Diamond-Like Carbon Coating for Drill Collars: Test Experiences

摘要

Failure of drill collars due to corrosion of non-magnetic collar materials is a challenging problem due to corrosion. Corrosion damages of the drill collars are usually on their internal surfaces due to aggressive mud chemistry (high content of H_2S, CO_2, dissolved oxygen, pH < 9, etc.) flowing through their annular side. To increase the corrosion resistance of non-magnetic drill collars, diamond-like carbon (DLC) coating was applied on long internal surfaces of collars and tested. Roll-bending, fatigue, erosion and microstruclural examinations were performed. Based on encouraging results of laboratory-based studies, field tests were performed. During field test, in HC1 acid (used to release the collar) condition, challenges were faced. This paper deals with the laboratory test results and challenges faced during field tests. Possible causes of damages of the DLC coating in HC1 acid conditions during field tests are also discussed.