Experimental Study Of Inhibitors Of Gas Hydrate

In deep water drilling, Natural gas hydrate can be formed in wellbore, wellhead tubes and subsea pipelines, which is harmful for the safety of oil & gas production and transportation. The prevention of gas hydrate has been a challenge for the oil industry for many years. In this study, the conditions and mechanisms of natural gas hydrate formation in deep water operations have been analyzed. The inhibition performance of three gas hydrate inhibitors and their synergetic effects have been investigated using a stirrering type reactor at various conditions.Salts and organic solvents (like alcohols) are commonly used thermodynamic hydrate inhibitors, and NaCl and ethylene glycol (EG) were found to have a better inhibition effects, which have been used to mix with low dosage hydrate inhibitors, namely, the innovative kinetic and anti-agglomerant (AA) inhibitors for better effects.. Experimental study on the performance of a kinetic inhibitor (based on PVCap) has been conducted, and good results were obtained on different formulations of PVCap based solution with NaCl and EG.This study was also focused on design and experimental evaluation of a new AA inhibitor, based on quaternary ammonium salts. The influence of oil-water ratio, stirringspeed on the effect of the AA inhibitor was experimentally investigated. A best molecular formulation has been found and its effective concentration and capability are determined via experiments.The nucleation process and nucleation hypothesis of natural gas hydrate are analyzed in details in the last part of this dissertation in order to discuss the mechanism of the three types of hydrate inhibitors. Based on the mechanisms of hydrate formation and the inhibition effects of different types of inhibitors, a new formulation of hydrate inhibitor, which is a mixture based on a kinetic inhibitor while thermodynamic inhibitor and AA inhibitors as synergetic agents, was studied experimentally and obtained a good results. Finally, a molecular design of a new type hydrate inhibitor, which combine the effects both for kinetic and agglomeration control is proposed for future studies.