1 Office of Fossil Energy Detection and Production of Methane Hydrate

Disclaimer This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. The abundance and distribution of gas hydrate in marine sediment sequences depend on inputs and outputs of carbon over time. The primary input is solid organic carbon, which is converted to methane. The primary outputs for many systems are anaerobic oxidation of methane and gas burial. The primary scope of this task is to generate chemical constraints on carbon inputs and outputs, which can be incorporated into numerical models. We have generated almost all data and are beginning to incorporate into models. Accumulation of gas hydrate and free gas is modeled in heterogeneous marine sediments over geologic time scales. The two-dimensional numerical model incorporates deposition and compaction of heterogeneous sediments, methane generation, and migration of water with dissolved gas. Fracture network systems and dipping sand layers are common examples of lithologic heterogeneities in natural gas hydrate systems, and are simulated using the current 2-D model. Increased fluid flux within these high permeability conduits results in concentrated hydrate deposits. The upward flux of methane is an important determinant for the amount of hydrate that may potentially be present in the sediments. One approach to measure methane flux is to relate sulfate methane transition (SMT) depth to the methane flux via anaerobic oxidation of methane (AOM). Dickens suggests that AOM is the most dominant reaction in natural gas hydrate systems. However, numerous prominent authors such as Kastner et al. argue that consumption of pore water sulfate in shallow sediments is a result of oxidation of particulate organic carbon (POC) and not methane (Kastner et al., 2008). The articles in Fire in the Ice by Kastner et al., 2008 and Dickens …