Modelling sea gas hydrates
Large reservoirs of methane, an important greenhouse gas, have been discovered on the seafloor. The cold temperatures and high pressure of the deep sea promote the formation of gas hydrates, which lock molecules of methane inside water cages. Little is known about the processes driving the formation of these sea gas hydrates, yet there is concern about the global warming potential of the methane should it be released to the atmosphere. They might also be exploited as an energy source. The Technical University of Clausthal participated in an important FP5 project dedicated to improving our knowledge of gas hydrates. Their aim was to develop a model to describe the behaviour of the gas hydrates. A three-dimensional model was put together based on data collected at the Anaximander measurement site as well as from the relevant literature. Various modules address the initial conditions for gas hydrate nuclei, mechanisms for growth and decay, reaction kinetics that release methane to the water column, etc. The model addresses phenomena down to the millimetre scale, such as the effects of pore geometry and gas hydrate content on transmissibility. Once constructed, the model was then subjected to sensitivity studies in order to broaden its applicability and to identify possible weaknesses. The German scientists concluded that model output is extremely sensitive to the input data, especially in the case of the vertical flux of methane. In order to improve model performance, additional information must be acquired, including sediment permeability, the concentration and size distribution of gas hydrate nuclei and so on.
