In-situ H2 Generation from Hydrocarbons and CO2 Storage in the Reservoir

Hydrogen has a great potential as an environmentally clean energy fuel. The drawback, however, is that the modern methods of hydrogen production require significant amounts of energy and generate large volumes of CO2. The most common way of producing hydrogen today is a staged process including natural hydrocarbon gas production, its transport and processing, steam reforming and storage, followed by further transport and management of by-products such as CO2. A process allowing for generating hydrogen from hydrocarbons in situ could open a new immense source of clean hydrogen energy for commercial use. In the proposed novel concept the hydrogen generation process is carried out directly in the hydrocarbon reservoir. The reservoir is then converted into a ready to produce high pressure hydrogen storage cell. Hydrocarbon processing and transportation stages on the surface are therefore abated. The energy required for hydrogen production is significantly reduced with CO2 being captured and stored in-situ. In the "conventional" process capturing and storing CO2 from a power plant alone can increase the energy cost by up to 60%. In addition to energy saving the emissions of green house gases is wed out. In order to validate the concept of in situ hydrogen generation process several laboratory experiments were performed. The CO2 flooding experiments in the sandstone core at reservoir conditions indicated gravitational segregation of CO2 in the methane-carbon dioxide system. The hydrogen conversion experiment demonstrated feasibility of the suggested process. Catalytic experiments without optimising reaction conditions showed that resulted gas compositions can contain up to 55% of hydrogen. Thermodynamic calculations using experimental data allowed to evaluate relative importance of the reactions that may take place at given conditions. For the in-situ process a water soluble precursor can be placed in the reservoir using dedicated injection wells. Steam reforming temperatures may be reached with either steam injection or in-situ combustion resulting in required increase of reservoir temperatures. High thermal energy generated in situ may be utilised later by temporally using the injection wells as geothermal ones. Circulating water into these wells will allow to bring this thermal energy to the surface and to reduce the temperature in the reservoir. Reduction of the reservoir temperature from steam-vapour condition at hydrogen generation stage to conditions corresponding to condensation of water will have positive effect for separation of hydrogen in situ and CO2 dissolution in water. CO2 solubility in water is almost 700 times higher than solubility of H2. At cooler temperatures gravity segregation will effectively contribute to hydrogen segregation and accumulation of it in the upper parts of the geological structure. The commercial application of in-situ generation of hydrogen from hydrocarbons may be particularly relevant to • tight gas and shale gas reservoirs, • depleted and waterflooded oil fields, • coal bed methane deposits, • heavy oil, bitumen and shale oil deposits (in the form of in-situ upgrading of oil).