Reactivation of abandoned oil fields for cleaner energy generation

Given the global effort towards net zero carbon emissions, and specifically the UK government’s target to achieve this by 2050, it has never been more important to find sources of clean energy that are alterna-tives to the conventional use of fossil fuels. Clean energy can be defined as a zero-carbon emission source that does not release further polluting gases into the atmosphere. Use of enhanced geothermal systems is a promising method of clean energy production that can help to fill the gap in the energy supply; these sys-tems can be artificially created with the reactivation of abandoned oil fields. There are tens of thousands of abandoned oil fields that are no longer considered economically viable through conventional production methods yet still contain considerable resources. Abandoned oil fields can be reactivated using air-injection to produce clean energy via the direct use of heat generated in-situ. The new energy is a result of in-situ combustion as part of an enhanced geothermal system within a closed loop system. Historically conventional applications of in-situ combustion have experienced high failure rates in field applications, due mainly to a lack of understanding of how the subsurface geology of the pe-troleum system impacts the process. This thesis progresses through one-dimensional, two-dimensional, and then to three-dimensional models, building in complexity to ascertain the key variables that control the degree of success and potential ener-gy production of the application of in-situ combustion for enhanced geothermal systems. The models pre-sented in this research assess key input variables (porosity, permeability, heterogeneity distribution, and reservoir geometry) on the outputs including temperature, fire front velocity, propagation stability, and enthalpy generation. This work has revealed the end member controls on the success and potential energy generation of the reactivation of abandoned oil fields. The work has highlighted the importance of traditional reservoir quali-ty metrics such as porosity and permeability, and the importance of the properties of the oil in place in conjunction with the petrophysical properties, on the overall chances of success and the energy generat-ed. The research highlights the importance of understanding the type and distribution of heterogeneity and the geometry of the reservoir with regards to injection and production well positioning, with more homogenous reservoirs with less complicated geometry offering a preferable target. The models present-ed in this thesis reveal the first order interpretations on reservoir selection of fields that can be high-graded for further detailed modelling and laboratory experiments of the process of energy generation from in-situ combustion. This important screening step will allow for better selection of candidate reser-voirs based on an understanding of how basic reservoir quality parameters control the process, decreasing the number of complex fields models that need to be produced. Overall, high porosity, low permeability variation, and a low degree of heterogeneity presents the most ideal target, the Mariner field represents the most ideal candidate.