Using Stainless Steel Coiled Tubing in a Novel Application

Abstract Stainless steel coiled tubing (CT) was used for the first time in Spain in 1997, to convey a burner as part of an underground Coal Gasification feasibility project by Underground Gasification Europe (UGE). Minimizing the risk of combustion associated with contact between pure oxygen and carbon steel dictated the requirement of stainless steel coiled tubing for this project. Additionally, stainless steel CT was required to minimize the corrosive aggressiveness of pure oxygen. The 1.75" 316 L stainless steel coiled tubing used for this project, was milled in a continuous length in Switzerland and tested for its low cycle fatigue properties in Houston. Two stainless steel control lines were installed inside the coiled tubing to initiate the burning process, together with a thermocouple to monitor the down hole temperature during the gasification. This paper discusses the role that stainless steel coiled tubing played in this underground coal gasification project as well as the development and testing of all the components.