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ABSTRACT:Creation of a fracture network in a hydraulic fracturing process is essential for subsurface energy extraction and CO2 sequestration. It is facilitated by reactivation of pre-existing intersecting weak layers and cemented cracks in the rock. In this study, a poromechanical model is developed for the hydraulic fracturing process in rocks containing such pre-existing weak layers. Based on the mixture theory, the crack band model is used to simulate the growth of a crack system. The governing equations with the parameters for hydromechanical coupling are derived, to describe the evolution of the opening and branching of cracks caused by water injection. Microplane model M7 is adopted to characterize the deformation and fracturing of the solid skeleton of the rock, and the Poiseuille law is used to characterize fluid flow through the hydraulic fractures. Numerical simulations are performed to reproduce and interpret recently published laboratory-scale hydraulic fracturing experiments conducted at Los Alamos National Laboratory (LANL). In these experiments, the rock was represented by confined plaster slabs containing orthogonal intersecting weak layers of higher porosity. Numerical simulations reveal how poromechanical characteristics such as the Biot coefficient and the fluid injection rate lead to various typical fracture modes observed in the experiments. These modes include formation of one dominant planar crack or various orthogonal fracture networks.
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Probabilistic Estimation of Levelized Cost of Electricity from Using Geologically Stored CO2 for Geothermal Energy Production
The use of geologically stored CO2 as a geothermal heat extraction fluid can take advantage of the beneficial thermophysical characteristics of CO2 that can render it a more effective heat extraction fluid than the brine that exists in the aquifers. Some of these characteristics include a higher mobility (inverse kinematic viscosity) in reservoir conditions and a highly temperature-dependent density that can result in a naturally self-convecting thermosiphon between injection and production wells. This thermosiphon may reduce or eliminate the need for subsurface pumps—and the associated parasitic pumping power—for fluid circulation. Part of the utility of such a CO2 capture, utilization, and storage (CCUS) system is the possibility to generate baseload or dispatchable electricity with levelized costs of electricity (LCOEs) that are on par with the LCOEs of other energy technologies of regional electricity systems.
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- PAR ID:
- 10350881
- Date Published:
- Journal Name:
- Proceedings of the 15th International Conference on Greenhouse Gas Control Technologies, GHGT-15
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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