Tailoring Chemicals for Continuous Injection Downhole via Capillary Line and 'Sensitive' Jewelry

摘要

As offshore operators explore deeper waters and develop more mature oil and gas fields with complex well structural designs, new and different challenges are encountered that can impact production. Continuous downhole injection of chemicals is increasingly required to manage challenges, such as scale formation and corrosion within the wellbore completion components. Many challenges are met when designing and qualifying chemicals for continuous downhole injection via capillary line for such systems. Discussed herein are the physical properties production chemicals injected via capillaries should possess, including temperature stability, gunking, compatibility with process fluids, and efficiency. However, the main challenge and focus addresses the compatibility of neat chemicals with downhole jewelry materials. Two chemical qualification processes are discussed - a corrosion inhibitor and a combined corrosion- and scale inhibitor. The corrosion inhibitor is a synergistic blend of imidazoline salt and other surfactants, while the combined inhibitor is a synergistic blend of amine, terpolymer, and various additives. Both chemicals are tailored to reduce corrosion, while the combined inhibitor also inhibits mineral crystal growth. The products had to be tailored and qualified for capillary line injection with downhole parts made of UNS S41000, UNS N04405, and cemented tungsten carbide (91.6 HRA, 6% - 9% Co) as chemically wetted components at elevated temperatures. The chemicals have shown good performance and have satisfied defined requirements for safe deployment downhole.