Gas hydrates are crystalline solids consisting of cages of water molecules around a gas molecule such as methane. They are found in arctic regions and along the continental margins, and there are more hydrocarbons in gas hydrates than in all other sources of hydrocarbons together. Gas hydrates therefore represent a possible energy game-changer. In this project we address the underlying physical processes that limit to what degree gas hydrate production can be combined with CO2 storage. We have addressed processes across scales, from the atomic to the continuum. The long-term goal of this project has been to improve the production process and accelerate the rate at which CH4 can be replaced by CO2, thereby making production by replacement economically and technologically feasible.
Through this project we have developed new knowledge and insights into how fracture in materials that change their strength or volume through reactions, such as when methane is exchanged with CO2 in a gas hydrate, can accelerate the replacement process. On large scales, studies have been performed on analogue materials such as ultramafic rocks, because we have limited knowledge about the relevant material properties of gas hydrates. We have also developed new models for how we can couple fluid transport in fractures in gas hydrates and other materials to the fracturing of the material and the reaction between the fluid and the material. Based on these studies, we have mapped out what mechanisms are essential to accelerate the replacement process . These results may later be extended to allow us to determine when injection of CO2 in gas hydrates may accelerate the extraction of methane.
To improve our knowledge of the material properties of gas hydrates we have developed new models to study processes at the molecular level using molecular dynamics. These models allow us to understand and predict the mechanical properties of and transport of fluids in intact and disassociating gas hydrates. The models for gas hydrates demonstrate that the gas hydrates break down not due to unstable fractures, but due to slowly moving, thermally activated fracture processes. This has significant consequences for the strength of gas hydrates and at what temperature gas hydrates will disassociate due to temperature changes in the atmosphere or sea. We have also demonstrated how the strength of the hydrates depend on the grain configuration and how the strength changes when the hydrates are interlaced with minerals. The methods that have been developed have also been used to build a more general understanding of the formation of nanocrystals ? an important area in itself.
Through the project, we have developed international collaboration agreements with leading research groups at Columbia University and the University of Southern California in order to strengthen our competence in large-scale molecular simulations and in field-scale studies of relevant geological systems. We have also developed a new collaboration with Wuhan University in China on molecular modeling of gas hydrate processes. These collaborations will be important in the continued work to understand the behavior of gas hydrates and, in the longer term, to develop new methods for extraction of methane from gas hydrated through injection of CO2.
Gas hydrates are crystalline solids consisting of cages of water molecules around a gas molecule such as methane. They are stable at 0-10C at 300-600m and are found in arctic regions and along the continental margins. There are more hydrocarbons in gas hy drates than in all other sources of hydrocarbons together. Gas hydrates therefore represent a possible energy game-changer. However, it is currently not economically or technologically feasible or safe to produce hydrocarbons from gas hydrates at large sc ales. Gas hydrate production can be combined with CO2 storage by CO2 injection, but it is limited by slow exchange rates.
This project comprises fundamental research on how fracture and deformation of gas hydrates are related to the disassociation of the hydrates and to the possible replacement of methane by CO2. By understanding the underlying physical processes from atoms to the continuum, we aim to improve the production process and accelerate the conversion process. Our strategy involves three scient ifically coupled subprojects that combined will give new insights into the mechanisms of gas hydrate deformation and how it affects disassociation: Molecular dynamics simulations of fracturing during gas hydrate disassociation; Continuum scale simulation of coupled processes during gas hydrate disassociation; and Combining atomic and continuum results to improve production methods.
The project will be carried out at the Center for the Physics of Geological Processes, an established cross-disciplinary coll aboration between physics and geology lasting more than 15 years with a record of producing research of fundamental importance with practical applications. The center is therefore in a unique position to address the proposed cross-disciplinary project. Th rough strong international collaborations and extended international stays, we will build a local competence in atomic scale modeling, and open for networking, exchange of knowledge, and scientific visibility.