History and Evolution of the Product Selection Criteria for Selecting Kinetic Hydrate Inhibitors

Abstract

ABSTRACT Gas hydrate formation and control is a critical flow challenge that many offshore oil and gas production operations encounter. Formation of hydrates can cause blockage of production flowlines, chokes and valves, which can result in catastrophic failures. Compared to other production problems, hydrate formation is a relatively new phenomenon that is becoming more and more significant with increasing subsea and deepwater developments as well as huge gas projects in the Middle East. The use of low dosage hydrate inhibitors (LDHIs), such as kinetic hydrate inhibitors (KHIs), offer an alternate technical solution to thermodynamic hydrate inhibitors by offering better economics, improved Health, Safety and Environmental (HS&E) performance and less demand on product transportation and storage. This paper summarizes the history, evolution and current state of KHI laboratory testing requirements. Improvements in laboratory techniques to evaluate the performance of KHI in sweet and sour environments will be discussed. The results of the evaluation are based on laboratory conditions and the ability of a KHI to successfully inhibit hydrate formation in sweet and sour rocking cells. Recent testing has shown significant differences between sweet and sour environments and the ability of the KHI to successfully inhibit hydrate formation under laboratory conditions. The secondary properties of a selected KHI are becoming more important so are advances in evaluating these properties, in particular the stability and applicability of a KHI under proposed system conditions. Hydrates may form different structures depending on the gas composition of the produced fluids. The nature of the KHI used needs to take into consideration. Recent product developments in this area show that these challenges can be met with appropriate lab testing. INTRODUCTION Flow assurance is critical during the efficient production of hydrocarbons from offshore and subsea assets. Gas hydrate formation and control is a critical flow assurance challenge that many offshore oil and gas production operations encounter. The interaction of low-molecular weight gases such as small chain hydrocarbon, and acidic gases like carbon dioxide and hydrogen sulfide, with water under "high" pressure and "low" temperature within a pipeline can form gas hydrates. Gas hydrates are essentially a gas molecule encapsulated by water molecules which have an ice like appearance. Two types of hydrate structure form in gas pipelines, type II being the most common and associated with larger gas molecules such as ethane and propane and type I mainly associated with lean gas and/or carbon dioxide or hydrogen sulfide production. Gas hydrate crystals may agglomerate and/or anneal to form plugs that results in lost production and may incrase (HS&E) risks. Formation of hydrates can cause blockage of production flowlines, chokes and valves, which can result in potentially catastrophic failures.