Vinsamlegast notið þetta auðkenni þegar þið vitnið til verksins eða tengið í það: https://hdl.handle.net/1946/26598
Geothermal reservoir engineering provides various methods to study, analyse and predict the behaviour of a geothermal system. In this thesis, we use two, cost and time effective methods to study a low temperature geothermal system located in Munadarnes situated in west Iceland. By using these two models, we derive important properties of a geothermal reservoir in Munadanes. Reinjection is studied and used to improve the production potential of the reservoir. Injection of
cold fluid into hot geothermal reservoirs is formulated as conservation laws. The cold front velocity induced during injection has been computed from the literature from conservation of energy and the method of characteristics applied to an initial boundary value problem. This computed thermal front velocity is expressed as the ratio of the integral of the product of the internal energy and the energy flux to
the integral of the internal energy. In this thesis we present a new and innovative method for computing the thermal front velocity by solving a Riemann problem.
We show that the unique solution of the Riemann problem moves at the speed equal to the thermal front velocity. The thermal front velocity computed in this thesis is only expressed as the integral of the energy flux. Our result is computed from the Rankine-Hugoniot shock condition from the theory of hyperbolic conservation laws and is much easier to evaluate. It depends on the flux function of the conservation laws, the injected fluid temperature and the reservoir temperature. A relative
error of magnitude 10^-3 was observed between the result obtained in this thesis and the one from the literature. This shows that the two results are in good agreement.
By Applying lumped parameter modelling to well MN08 in Munadanes in west
Iceland, the size of the reservoir, base on an estimated 900 m reservoir depth, the permeability and the storage mechanism of the reservoir intersecting well MN08 are evaluated. Diverse injection scenarios are used to determine the optimum distance separating injection well and production well in Munadanes, in order to mitigate temperature drop due to cold water injection. The models used to compute the thermal front velocity assume that 100% of the injected fluid reaches the production
well. In reality only a fraction of the injected fluid reaches the production well.
For practical reinjection field study, a tracer test is recommended. In addition, the models are one dimension and could be extended to 2 or 3 dimensions.
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