Characterization of Gas Hydrate Formation and Deposition using Dielectric Measurements
Joint conference paper with Statoil held at the 9th International Conference on Gas Hydrates
A shift in hydrate control strategies from avoidance to management, implies a need for assessment of the risk of hydrate deposition in oil and gas pipelines and production systems. There is thus an increased need for knowledge on hydrate deposit mechanisms and properties. In order to investigate the fundamental aspects of deposition mechanisms in hydrate experiments, sensor technologies that are able to detect hydrate formation and characterize hydrate deposition layers of varying thicknesses are required.
The dielectric properties of gas hydrates differ significantly from those of water, oil, gas and oil/water mixtures. Dielectric spectroscopy is therefore considered to be an viable technology for monitoring hydrate formation and growth. Christian Michelsen Research (CMR) has developed a dielectric spectroscopy measurement system for characterization of gas hydrates, based on broad-band permittivity measurements with open-ended coaxial probes. The technique is sensitive for early deposition close to the pipe wall, and onset and growth of thin hydrate layers can be monitored. Further on, experiments show that hydrate wetness can be estimated from the measured dielectric spectra due to the large contrast between water permittivity and hydrate permittivity. This system is applicable for both laboratory scale characterization of gas hydrates and on-line monitoring in pipelines. The aim of this paper is to present research results from both bench-scale tests and high pressure flow loops.
Tests on ice and atmospheric pressure model systems (using cyclopentane and tetrahydrofuran as hydrate former) have been used to characterize the sensor systems, and measurements on high pressure crude oil (using live crude oils and associated process waters) and gas systems (using a mix of methane and propane as the hydrate former) were used to verify the ability of the sensor systems for real gas hydrate systems under controlled conditions. Measurements in a high pressure flow loop were conducted to test the system under realistic multiphase flow conditions