Aliyu, Musa Dahiru (2018) Hot dry rock reservoir modelling. PhD thesis, University of Greenwich.

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Abstract

Geothermal energy reserves are significantly underdeveloped resources, and field experiments have shown the energy produced from this resource is clean and sustainable. Deep geothermal resources represent one form of geothermal energy, and the most widely used, in terms of commercial viability, are the hot dry rock (HDR) geothermal reservoirs. The field investigation of HDR systems is costly. The interaction between key rock properties during reservoir operation requires clear understanding to predict long-term performance. Therefore, there is a need for a numerical modelling tool to capture the coupled interactions between the thermal, hydraulic, mechanical and chemical processes operating during exploration-exploitation.

A multitude of computational models have been developed over the past two decades, based on different modelling approaches; however, there are still some limitations associated with their conceptual models concerning their ability to capture the structures present in deep subsurface media. To address some of these shortcomings, a fully coupled transient thermohydraulic (TH)model of an HDR geothermal reservoir is developed using the finite element method. The model is developed based on the open outlooks of HDR geothermal reservoir concepts established in the US, UK and France and is carried out following an intense review, with the identification of research limitations and shortcomings. Before that, the governing equations are derived based on the conservation laws of mass, energy and momentum from modifying the existing equations used.

Moreover, extensive verifications and validations are conducted to evaluate the efficiency and reliability of the developed model based on well-established analytical solutions and experimental field measurements available in the related literature, and the results obtained are in good agreement. Subsequently, additional extensions are examined based on the limitations of the previous techniques identified. The aforementioned additions include simulation of a field case study, modelling of heterogeneous HDR systems, and the effect of multiple pore media in probing the productivity of reservoirs during long-term performance. Thus, these three contributions represent a more realistic model of reservoir concepts that account for the faults, fractures and rock matrix concurrently. The different sets of the results obtained from these models are analysed in-depth, and several breakthroughs are identified that advance the knowledge in the field of geotechnical engineering and particularly HDR geothermal systems.

This present work has shown the modelling of geothermal systems can be improved by using field data selectively with existing methods. The key outcome from this research is new insight into the way geothermal energy reserves can be exploited, and modelled. This work shows that a computational modelling approach can increase our understanding of complex subsurface interactions in geothermal reservoirs, and how they can be simulated effectively.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	Geothermal energy; HDR geothermal energy; HDR simulation methods; HDR energy mining; numerical modelling;
Subjects:	H Social Sciences > HD Industries. Land use. Labor T Technology > TJ Mechanical engineering and machinery
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > School of Engineering (ENG)
Last Modified:	17 Apr 2019 16:18
URI:	http://gala.gre.ac.uk/id/eprint/23637

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