GOALI: Structure and Stability of Gas Hydrates - Probing the Mechanism of Binary Gas Hydrate Decomposition

Colorado School Of Mines, Golden CO

Investigators

Abstract

Sloan, E. Dendy et al / Jefferson L. Creek Colorado School of Mines / ChevronTexaco "GOALI: Structure and Stability of Gas Hydrates - Probing the Mechanism of Binary Gas Hydrate Decomposition." Methane, ethane and carbon dioxide are three of the most important natural gas hydrates. These are potential rich energy sources. Double hydrates of methane + ethane and methane + carbon dioxide span a size range suitable to provide detailed experimental and theoretical investigations of Structure I and Structure II hydrates at equilibrium and during decomposition. The experimental techniques to be used in the proposed work are NMR spectroscopy and neutron diffraction. This project proposes to measure pressure-temperature-composition relations in the methane + ethane and methane + carbon dioxide double hydrate systems. The proposed work will study hydrate decomposition as well as equilibrium properties of these double hydrates as a function of three variables: . The gas phase composition for methane mole fractions of 0 to 1. . The temperature range of 233 to 283 K. . The pressure range of about 450 to 4000 kPa. The proposed work will develop quantitative models based on the molecular size -- cavity size ratio concept to be used to predict the structure and stability of natural gas hydrates. These models will be developed from theoretical Langmuir adsorption coefficient calculations. At equilibrium the double hydrates methane + ethane and methane + carbon dioxide are particularly appropriate for these types of studies because methane + carbon dioxide should only form Structure I hydrate while the methane + ethane and theoretical studies in the proposed work provide for a molecular level understanding of gas hydrate. The broader impacts including educational and technical are as follows: The proposed work will help foster both graduate and undergraduate education and research in the chemical sciences at the Colorado School of Mines. Both graduate and undergraduate students who participate in the proposed work are expected to publish the results of their work in peer-reviewed journals and to attend scientific conferences in order to present results based on their work. The students and project in general will benefit from the intellectual collaboration with Dr. J. Creek (co-PI) of ChevronTexaco Energy Technology Company. Dr. Creek will help guide the project team on the industrial relevance of the work. Strategies for energy resource recovery and hydrate plug remediation in the gas and oil energy industries will also benefit from the knowledge generated in the proposed work. The amount of gas contained in hydrate formations depends on the hydrate structure and guest fractional occupancy. Hydrate plug structure and formation conditions will also be better understood based on information developed in the project.