Thermal well service conditions have presented a significant challenge to the sealability of casing connections. Over the years, industry has established various standards, protocols and guidelines for assessing the sealability performance of casing connections to be used in thermal well applications. The use of Finite Element Analysis (FEA) has been increasingly incorporated into the connection performance evaluation process. FEA evaluation requires the use of an appropriate criterion that relates the connection seepage rates to the applied internal pressure differential, contact stress profile on the radial seal surface, surface roughness, thread compounds and various other factors such as environmental impacts.
This paper presents experimental work that has been undertaken to investigate the metal-to-metal seal behavior in premium casing connections. The physical tests simulated a series of metal-to-metal seals under various levels of gas pressure and seal contact stress. The impacts of seal length, tubular diameter, surface roughness, thread compound and corrosive medium were investigated. The experimental results were used to validate the sealability criterion which is proposed for use in evaluating thermal well casing connections.