ABSTRACT:

In deep and cold waters, the formation of gas hydrates can create serious safety and operational problems, including plugging of the BOP, choke and kill lines. The use of thermodynamic inhibitors to suppress the formation of hydrates when the drilling fluid is static has been well documented in the literature. Unfortunately, these widely used inhibitors have a number of temperature and pressure limitations that significantly restrict their effectiveness, particularly in the ultra-deep and colder waters. To be effective under these conditions, the concentration of thermodynamic inhibitors must be above 40% of total fluid volume. Thus, the mud is transformed from a drilling fluid system to one functioning solely as an inhibitor. Additionally, in many parts of the world, environmental regulations restrict the use of some thermodynamic inhibitors. There also are operational restrictions, where high concentrations of thermodynamic inhibitors can hinder the testing and logging of a wellbore. This paper describes the development of kinetic inhibitors that supplement thermodynamic inhibition to effectively delay the formation of gas hydrates for more then 12 hours. The combination of the two inhibition agents not only represses the development of gas hydrates in extremely cold and pressured environments, but also can be used effectively in concentrations as low as 1% of total fluid volume. The dramatically lower concentrations thereby mitigate the environmental and operational limitations. The authors will discuss the development of the new kinetic inhibitors, which included laboratory testing equipment. Analysis of extensive laboratory test data and sample fluid formulations will be discussed in detail.

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