Effect of Sediment Composition on the Uniformity of Experimentally-Formed Methane Hydrate

• Main Author: Ryan, Terrence R.
• Format: Text
• Language: unknown
• Published: The Research Repository @ WVU 2012
• Subjects: Chemical engineering; Geology; Petroleum engineering; Methane hydrate
• Online Access: https://researchrepository.wvu.edu/etd/184; https://researchrepository.wvu.edu/cgi/viewcontent.cgi?article=1187&context=etd

Experimentalists that try to duplicate the methane hydrate found in natural systems have regularly made non-uniform hydrate in packed sediments. Some element of the natural system is missing from the experimental procedure. The goal of this research was to discover what role sediment composition and grain size play in the uniformity of experimentally-formed methane hydrate. The discoveries were quite surprising.;The motivation for this research lies in the analysis of sediment samples and well-log data from the 2010 Mount Elbert, AK Stratigraphic Test Well. Sedimentological analysis of core samples from this well indicated that a thin section within the methane hydrate formation lacked the kaolinite clay that was found throughout the rest of test well. This section also corresponded to a void in the methane hydrate saturation. Thus, a hypothesis was developed which states that a critical amount of clay (such as kaolinite) is needed in a sediment matrix for a uniform methane hydrate formation to occur.;To test the hypothesis, a three-part experiment was performed. First, a method of manufacturing artificial sediments was developed. This produced material which was appeared very similar to natural sediments using Scanning Electron Microscopy. Secondly, in order to achieve packing characteristics similar to a natural environment, a centrifuge-based sediment packing system was constructed, and a sediment packing procedure was developed. Lastly, the packed artificial sediment was used in a methane hydrate formation experiment conducted in a Computed Tomography (CT) Scanner. Use of the CT scanner would allow imaging of the resultant methane hydrate formation.;A total of three experiments were conducted. Two experiments were conducted on sediments containing quartz grains mixed with kaolinite clay. The third experiment was conducted on sediment containing only quartz. In the two experiments involving kaolinite-quartz sediments, the resulting methane hydrate formation was highly uniform. The methane hydrate formed in the quartz-only sediment was highly non-uniform.;The positive effect of the kaolinite clay on the uniformity of a methane hydrate formation is therefore taken to be true. The presence of clay in sediment allows water to be distributed uniformly. If the water is distributed uniformly, the resultant methane hydrate should be uniformly distributed, as well. The water is not subject to rapid movement during the methane hydrate formation from gravity or concentration gradients.;To the knowledge of those involved in this work, this is the first time uniform methane hydrate has been formed in artificial packed sediment. Other experimentalists can apply these techniques to their own work and broaden the knowledge base of the hydrate community. This discovery may also help explain why hydrate does not form properly in what may be an otherwise perfect environment. This work is just the beginning.