Did melting glaciers cause volcanic eruptions in eastern California? Probing the mechanics of dike formation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94661/1/jgrb14086.pd

Synchrotron-based pore-network modeling of two-phase flow in Nubian Sandstone and implications for capillary trapping of carbon dioxide

Depleted oil fields in the Gulf of Suez (Egypt) can serve as geothermal reservoirs for power generation using a CO2-Plume Geothermal (CPG) system, while geologically sequestering CO2. This entails the injection of a substantial amount of CO2 into the highly permeable brine-saturated Nubian Sandstone. Numerical models of two-phase flow processes are indispensable for predicting the CO2-plume migration at a representative geological scale. Such models require reliable constitutive relationships, including relative permeability and capillary pressure curves. In this study, quasi-static pore-network modelling has been used to simulate the equilibrium positions of fluid-fluid interfaces, and thus determine the capillary pressure and relative permeability curves. Three-dimensional images with a voxel size of 0.65 micro m3 of a Nubian Sandstone rock sample have been obtained using Synchrotron Radiation X-ray Tomographic Microscopy. From the images, topological properties of pores/throats were constructed. Using a pore-network model, we performed a sequential primary drainage-main imbibition cycle of quasi-static invasion in order to quantify (1) the CO2 and brine relative permeability curves, (2) the effect of initial wetting-phase saturation (i.e. the saturation at the point of reversal from drainage to imbibition) on the residual-trapping potential, and (3) study the relative permeability-saturation hysteresis. The results improve our understanding of the potential magnitude of capillary trapping in Nubian Sandstone, essential for future field-scale simulations. Further, an initial basin-scale assessment of CO2 storage capacity, which incorporates capillary trapping, yields a range of 14-49 GtCO2 in Nubian Sandstone, Gulf of Suez Basin

CO2-Plume Geothermal (CPG) Heat Extraction in Multi-layered Geologic Reservoirs

AbstractCO2-Plume Geothermal (CPG) technology involves injecting CO2 into natural, highly permeable geologic units to extract energy. The subsurface CO2 absorbs heat from the reservoir, buoyantly rises to the surface, and drives a power generation system. The CO2 is then cooled and reinjected underground. Here, we analyze the effects of multi-layered geologic reservoirs on CPG system performance by examining the CO2 mass fraction in the produced fluid, pore-fluid pressure buildup during operation, and heat energy extraction rates. The produced CO2 mass fraction depends on the stratigraphic positions of highly permeable layers which also affect the pore-fluid pressure drop across the reservoir

COUPLING AND DECOUPLING OF HEAT AND HELIUM TRANSPORT IN A GEOTHERMAL RESERVOIR

ABSTRACT We present two-and three-dimensional simulations of heat and helium transport for a generalized graben system to systematically investigate how various interacting parameters influence coupling and decoupling of magmatic or mantle heat and helium signals in the Earth's crust. We confirm findings of previous studies by other authors including the occurrence of spatial decoupling of heat and helium due to variations in their respective diffusivities, entrapment of helium by low permeability layers, and the preference of helium for fracture flow. We continue by assessing the impact of radiogenic heat and helium production and buoyancy-driven convection within a fracture system and within a crystalline basement layer on the distribution of temperature, helium, and isotopic helium ratios. We find that processes deep within the subsurface can have a large effect on near-surface mantle/magmatic heat and helium signatures even though such near-surface measurements are typically used to infer deep groundwater and heat flow vector fields. Additionally, we show the significance of distinguishing between heat and helium signal decoupling due to transport phenomena and due to other subsurface processes. The results of our investigation have applications to geothermal reservoir analyses, mantle heat versus mantle helium estimations, and studies using heat and/or helium as natural tracers of groundwater flow