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Presenter: Dr. Matthew Clarke - Department of Mechanical and Manufacturing Engineering, University of Calgary
Supervisor:

Date: Thu, March 6, 2003
Time: 11:00:00 - 00:00:00
Place: EOW 430

ABSTRACT

Abstract:

The forward beam reflectance method (FBRM) provides online and in-situ information about the chord length distribution of a population of particles in a solid-liquid slurry. This is a significant advantage over conventional instruments that require sampling and dilution. Because it is capable of operating at high pressures, the FBRM is useful for studying the kinetics of gas hydrate crystal growth.

Gas hydrates constitute a class of solids in which small molecules occupy almost spherical holes in ice-like lattices made up of hydrogen-bonded water molecules. This class of solids is known as clathrates. Gas hydrates are crystalline compounds and can exist in one of four structures; structure I (sI) and structure II (sII), structure H and a new, as of yet unnamed structure.

Gas hydrates have significant importance in the petroleum industry. Traditionally, for the transportation of oil and gas, the industry has designed pipelines to operate outside hydrate forming conditions. This has been accomplished by either adding traditional inhibitors such as glycols and methanol or by dehydration of the gas/condensate fluids. One major task encountered by the petroleum industry is to decompose a hydrate plug formed accidentally or otherwise. Having reliable data on the intrinsic kinetics of gas hydrate decomposition could allow for better predictions of the rates of decomposition in hydrate plugs.

On the other hand, in-situ hydrates found in permafrost regions and under the ocean floor represent a vast, untapped natural resource. In order to predict gas production rates from hydrate reservoirs, it is necessary to be able to account for the rate at which hydrates are decomposing.

Experiments were conducted with methane at pressures ranging from 32 bar up to 60 bar and over a temperature range of 274.15 K to 281.15 K and the results were analysed using the model of Clarke and Bishnoi (1999). The forward beam reflectance method made it possible to continuously observe the chord length distribution during the experiment. It was found that both the formation and decomposition kinetics followed an Arrhenius relationship.