Development of hydrate inhibition monitoring and initial formation detection techniques

Abstract

Prevention of gas hydrate blockages is a major challenge posed to the petroleum industry because uncontrolled formation of hydrate may result in plugging of transport pipelines, causing considerable production loss and personnel safety hazard. Injection of hydrate inhibitors is the most common option to prevent hydrate formation. In current industrial practice the dosage of hydrate inhibitor is estimated and injected upstream without much downstream measurements. Therefore, hydrate blockages are still encountered in the oil and gas industry due to lack of any hydrate monitoring measures against unexpected changes. In this thesis, novel techniques have been developed for monitoring hydrate inhibition and detecting early signs of hydrate formation based on downstream sample analysis and online measurements. The main achievements of this study can be categorised as follow: 1. Hydrate Inhibition Monitoring Techniques: Three techniques, i.e. conductivity-velocity (C-V) technique, water activity technique and water content technique, have been developed for determining optimising inhibitor injection rates 2. Initial Hydrate Formation Detection Techniques: The main objective of detecting early signs of hydrate formation is to give the operators adequate time to prevent hydrate formation and start remediation actions. Two techniques including the onset of hydrate formation and compositional change have been developed for detecting initial hydrate formation 3. Development of prototypes: Following the above fundamental studies, prototypes of the CV and water activity methods have been developed The development of hydrate inhibition monitoring and early hydrate formation detection techniques opens a novel flow assurance approach for the oil and gas industry. The developed hydrate monitoring techniques like the C-V technique, water activity and content techniques can be used to optimise hydrate inhibitor injection. In the near future, further development of the investigated early hydrate formation detection techniques like gas compositional change technique could provide an effective measure to minimise the risk of hydrate blockage.