LAUSR

Abstract Natural gas hydrates are crystalline solids made up of water and guest molecules. The most common hydrate formers are usually low-molecular-weight hydrocarbons typically found in natural gas. Salts, such as NaCl and CaBr2, can depress the water melting point temperature as well as hydrate formation conditions. Glycols, such as MEG, and alcohols, such as MeOH, have similar inhibitive effects to salts. Hydrate phase equilibria are of interest because hydrate solids in the pipes can jeopardize normal operation. However, the data for hydrate formation are limited under typical wellbore conditions, i.e., high pressure and high concentration of salts with organic inhibitors. Commonly used commercial software for hydrate phase equilibria shows unreliable predictions at these conditions. To improve the predictions, we have developed a simple but robust correlation, named Hu-Lee-Sum (HLS) correlation, to predict the hydrate suppression temperature with typical salts and organic inhibitors. To benchmark the predictions for hydrate dissociation, we herein report the experimental measurements for hydrate phase equilibria for brines and brine blends with MEG or MeOH, over a wide range of pressure. The measured data are compared to the predictions of three prediction tools (HLS correlation, PVTsim®, Multiflash®). For the systems and conditions tested, the HLS correlation shows robustness and accuracy, while PVTsim® and Multiflash® can be unreliable and in some cases give predictions with large deviations.