Assessing Natural Gas Versus CO2 Potential Underground Storage Sites in Greece: A Pragmatic Approach †

Although subsurface traps have been regularly explored for hydrocarbon exploration, natural gas and CO2 storage has drawn industrial attention over the past few decades, thanks to the increasing demand for energy resources and the need for greenhouse gas mitigation. With only one depleted hydrocarbon field in Greece, saline aquifers, salt caverns and sedimentary basins ought to be evaluated in furtherance of the latter. Within this study the potential of the Greek subsurface for underground storage is discussed. An overview and re-evaluation of the so-far studied areas is implemented based on the available data. Lastly, a pragmatic approach for the storage potential in Greece was created, delineating gaps and risks in the already proposed sites. Based on the above details, a case study for CO2 storage is presented, which is relevant to the West Katakolo field saline aquifer.

Geobiological features of storage hydrogen-methane mixtures in underground reservoirs

Taking into account the world and domestic experience of studying the ontogenesis of lithospheric hydrogen a combination of coupled hydrochemical, geochemical and microbiological factors of the accumulation of this natural gas together with methane in the terrigenous formations of the sedimentary cover is justified. It is predicted that various hydrochemical and microbiological processes that cause the development of carbon dioxide and sulfate corrosion of engineering structures, as well as cement of reservoir rocks and tires, can occur together with methane at industrial facilities of underground storage of hydrogen. The risks of reducing the volume of injected hydrogen in underground storage in addition to diffusion losses can be associated with geobiological factors, including the conversion of hydrogen into CH4 and H2S due to microbial activity, chemical interaction of hydrogen with minerals of reservoirs and tires, accompanied by changes in filtration-capacity and geomechanical properties, hydrogen embrittlement of metal structures of ground and underground well equipment. Keywords: geobiology; hydrogen; methane; underground storage; methanogenesis; acetogenesis; sulfate reduction.

Investigating the Effective Resistivity of Reinforced Concrete Waste Storage Tanks at the Hanford Site

Industrialized sites pose challenges for conducting electrical resistivity geophysical surveys, as the sites typically contain metallic infrastructure that can mask electrolytic-based soil and groundwater contamination. The Hanford site in eastern Washington State, USA, is an industrialized site with underground storage tanks, piping networks, steel fencing, and other potentially interfering infrastructure that could inhibit the effectiveness of electrical resistivity tomography (ERT) to map historical and monitor current waste releases. The underground storage tanks are the largest contributor by volume to subsurface infrastructure and can be classified as reinforced concrete structures with an internal steel liner. Directly measuring the effective value for the electrical resistivity of the tank, i.e., the combination of individual components that comprise the tank’s shell, is not reasonably possible because they are buried and dangerously radioactive. Therefore, we indirectly assess the general resistivity of the tanks and surrounding infrastructure by developing synthetic ERT models with a parametric forward modeling study using a wide range of resistivity values from 1×10−6 to 1×104 ohm-m, which are equivalent to steel and dry rock, respectively. The synthetic models used the long-electrode ERT method (LE-ERT), whereby steel cased metallic wells surrounding the tanks are used as electrodes. The patterns and values of the synthetic tomographic models were then compared to LE-ERT field data from the AX tank farm at the Hanford site. This indirect method of assessing the effective resistivity revealed that the reinforced concrete tanks are electrically resistive and the accompanying piping infrastructure has little influence on the overall resistivity distribution when using electrically based geophysical methods for characterizing or monitoring waste releases. Our findings are consistent with nondestructive testing literature that also shows reinforced concrete to be generally resistive.