High-Fidelity Evaluation of Hybrid Gas Hydrate Inhibition Strategies

In subsea oil and gas production, a transition away from complete gas hydrate avoidance to risk-based hydrate management has the potential to offer cost savings and improved viability for new developments. Rigorous characterization of hydrate formation probability (via the measurement of statistically significant numbers of independent hydrate formation events) represents a crucial step toward accurate quantification of hydrate blockage risk. Such characterization is especially pertinent when deploying low-dosage kinetic hydrate inhibitors (KHIs), which, unlike thermodynamic hydrate inhibitors (THIs), affect hydrate formation kinetics rather than thermodynamic stability envelopes. Here, we demonstrate the use of a second-generation, Peltier-cooled, high-pressure, stirred, automated lag time apparatus (HPS-ALTA) to efficiently measure hydrate formation under conditions simulating a methane-dominant natural gas asset. Over 2500 hydrate formation events were measured using a low-salt-content brine, enabling the production of smooth, high-resolution hydrate probability distributions in the presence of three inhibitor chemical additives and combinations thereof (a corrosion inhibitor, a KHI, and a conventional THI). Beyond enabling rapid, high-fidelity testing of potential inhibitor interactions, the results explicitly demonstrate the ability to effectively manipulate formation probability boundaries via a combination of thermodynamic and kinetic inhibition effects. Such hybrid inhibition strategies can be used to achieve long induction times at operationally relevant formation temperatures (over 2 days at 2.5 °C in this study) and may be more beneficial and/or cost-effective than strategies focused on complete hydrate avoidance.