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" Fractal and Anomalous Diffusion Models for Analyzing Well Test Data from Liquid Dominated and Vapor Dominated Geothermal Reservoirs "
Ozkan, Yasin
Onur, Mustafa
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1058695
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| Doc. No
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TL57812
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| Main Entry
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Ozkan, Yasin
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| Title & Author
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Fractal and Anomalous Diffusion Models for Analyzing Well Test Data from Liquid Dominated and Vapor Dominated Geothermal Reservoirs\ Ozkan, YasinOnur, Mustafa
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| College
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The University of Tulsa
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| Date
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2020
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| Degree
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M.Eng.
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| student score
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2020
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| Note
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182 p.
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| Abstract
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The importance of geothermal reservoirs is rising day by day because of the world’s enormous energy demand. Now, governments give special emphasis to renewable energy sources like geothermal energy more than fossil fuels since these renewable energy sources are considered environmentally friendly and sustainable. On the other hand, one of the most challenging tasks of geothermal reservoirs is to model these reservoirs for resource evaluation and performance analysis because geothermal reservoirs are quite heterogeneous and include complex network of fractures and faults. Appropriate modeling of geothermal reservoirs is crucial for determining appropriate production strategies. For instance, the effects of production and/or injection wells, and the locations of those wells on reservoir performance are assessed by the reservoir model. In addition to these, enhanced recovery production, injection wells operations, production rate prediction, and feasibility analysis of given field are determined by considering reservoir models. Hence, reservoir models are extremely important for companies. Well testing is applied to reservoirs to investigate the efficiency of the wells by companies. They characterize well performance and reservoirs by utilizing well-test data. The objective of this study is to apply fractal and anomalous diffusion models to geothermal reservoirs to analyze the well-test pressure data acquired from such reservoirs. These models are applied to well-test data to find reservoir parameters governing the resource potential and production rate performance, such as porosity and permeability. In this study, the diffusivity equations based on the fractal and anomalous diffusion concepts were solved by considering three different production boundary conditions; specified constant rate production, specified constant bottomhole pressure production, and variable rate/variable bottomhole pressure conditions. For all cases, the reservoir is assumed to be infinite acting. For each production boundary condition, the initial value problem (IBVP) was solved by using the Laplace transformation method and the Laplace space solutions were converted to the real time domain by numerical inversion using Stehfest’s inversion algorithm. Both dimensional and dimensionless solutions were presented for each condition and model. These solutions are compared, and the differences were determined and presented for each condition. Then, the solutions based on the fractal and anomalous diffusion models were applied to analyze well-test data from the Kizildere geothermal field in Turkey and the Kamojang geothermal field from Indonesia. Each geothermal field is examined to estimate the reservoir parameters by applying automated history matching based on the ensemble smoother with multiple data assimilation (ES-MDA) method. The main conclusion is that fractal parameters have a remarkable effect on the reservoir characteristics. Changing fractal parameters results in different reservoir characteristics. Fractal parameters cannot be interpreted from well test data, so the box-counting method is extremely important. Furthermore, fractal model achieves very good results for both the liquid-dominated and vapor-dominated reservoirs. On the other side of the coin, the Raghavan anomalous model’s performance should not be ignored for vapor-dominated reservoirs.
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| Descriptor
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Petroleum engineering
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Onur, Mustafa
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The University of Tulsa
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