Waterflood optimization via rate control is receiving increased interest because of rapid developments in the smart well completions and I-field technology. The use of inflow control valves (ICV) allows us to optimize the production/injection rates of various segments along the wellbore, thereby maximizing sweep efficiency and delaying water breakthrough. It is well recognized that field scale rate optimization problems are difficult because they often involve highly complex reservoir models, production and facilities related constraints and a large number of unknowns. Some aspects of the optimization problem have been studied before using mainly optimal control theory. However, the applications to-date have been limited to rather small problems because of the computation time and the complexities associated with the formulation and solution of adjoint equations. Field-scale rate optimization for maximizing waterflood sweep efficiency under realistic field conditions has still remained largely unexplored. We propose a practical and efficient approach for computing optimal injection and production rates and thereby manage the waterflood front to maximize sweep efficiency and delay the arrival time to minimize water cycling. Our work relies on equalizing the arrival times of the waterfront at all producers within selected sub-regions of a water flood project. The arrival time optimization has favorable quasi-linear properties and the optimization proceeds smoothly even if our initial conditions are far from the solution. We account for geologic uncertainty using two optimization schemes. The first one is to formulate the objective function in a stochastic form which relies on a combination of expected value and standard deviation combined with a risk attitude coefficient. The second one is to minimize the worst case scenario using a min-max problem formulation. The optimization is performed under operational and facility constraints using a sequential quadratic programming approach. A major advantage of our approach is the analytical computation of the gradient and Hessian of the objective which makes it computationally efficient and suitable for large field cases. Multiple examples are presented to support the robustness and efficiency of the proposed optimization scheme. These include several 2D synthetic examples for validation purposes and 3D field applications.

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We investigate systems with a mixed phase space, where regular and chaotic dynamics coexist. Classically, regions with regular motion, the regular islands, are dynamically not connected to regions with chaotic motion, the chaotic sea. Typically, this is also reflected in the quantum properties, where eigenstates either concentrate on the regular or the chaotic regions. However, it was shown that quantum mechanically, due to the tunneling process, a coupling is induced and flooding of regular islands may occur. This happens when the Heisenberg time, the time needed to resolve the discrete spectrum, is larger than the tunneling time from the regular region to the chaotic sea. In this case the regular eigenstates disappear. We study this effect by the time evolution of wave packets initially started in the chaotic sea and find increasing probability in the regular island. Using random matrix models a quantitative prediction is derived. We find excellent agreement with numerical data obtained for quantum maps and billiards systems. For open systems we investigate the phenomenon of flooding and disappearance of regular states, where the escape time occurs as an additional time scale. We discuss the reappearance of regular states in the case of strongly opened systems. This is demonstrated numerically for quantum maps and experimentally for a mushroom shaped microwave resonator. The reappearance of regular states is explained qualitatively by a matrix model. / Untersucht werden Systeme mit gemischtem Phasenraum, in denen sowohl reguläre als auch chaotische Dynamik auftritt. In der klassischen Mechanik sind Gebiete regulärer Bewegung, die sogenannten regulären Inseln, dynamisch nicht mit den Gebieten chaotischer Bewegung, der chaotischen See, verbunden. Dieses Verhalten spiegelt sich typischerweise auch in den quantenmechanischen Eigenschaften wider, so dass Eigenfunktionen entweder auf chaotischen oder regulären Gebieten konzentriert sind. Es wurde jedoch gezeigt, dass aufgrund des Tunneleffektes eine Kopplung auftritt und reguläre Inseln geflutet werden können. Dies geschieht wenn die Heisenbergzeit, das heißt die Zeit die das System benötigt, um das diskrete Spektrum aufzulösen, größer als die Tunnelzeit vom Regulären ins Chaotische ist, wobei reguläre Eigenzustände verschwinden. Dieser Effekt wird über eine Zeitentwicklung von Wellenpaketen, die in der chaotischen See gestartet werden, untersucht. Es kommt zu einer ansteigenden Wahrscheinlichkeit in der regulären Insel. Mithilfe von Zufallsmatrixmodellen wird eine quantitative Vorhersage abgeleitet, welche die numerischen Daten von Quantenabbildungen und Billardsystemen hervorragend beschreibt. Der Effekt des Flutens und das Verschwinden regulärer Zustände wird ebenfalls mit offenen Systemen untersucht. Hier tritt die Fluchtzeit als zusätzliche Zeitskala auf. Das Wiederkehren regulärer Zustände im Falle stark geöffneter Systeme wird qualitativ mithilfe eines Matrixmodells erklärt und numerisch für Quantenabbildungen sowie experimentell für einen pilzförmigen Mikrowellenresonator belegt.

This work investigates the performance of CO₂ soluble surfactants used for CO₂ foam flooding in fractured carbonate reservoirs. Oil recovery associated with the reduction of CO₂ mobility in fractures is assessed by monitoring oil saturation and pressure drops during injection of CO₂ with aqueous surfactant solution in artificially fractured carbonate cores. Distinct novel CO₂ soluble surfactants are evaluated as well as a conventional surfactant. Water flooding and pure CO₂ injection are conducted as baseline. Characterization of fluids and rock are also reported which include Amott test, oil phase behavior and slim tube test. Transport and thermodynamic properties of surfactant and supercritical CO₂ are used to evaluate the process on a core scale using a commercial reservoir simulator. / text

Minimum miscibility pressure (MMP) is a key parameter in the design of gas flooding. There are experimental and computational methods to determine MMP. Computational methods are fast and convenient alternatives to otherwise slow and expensive experimental procedures. This research focuses on the computational aspects of MMP estimation. It investigates the shortcomings of the current computational models and offers ways to improve the robustness of MMP estimation. First, we develop a new mixing cell method of estimating MMP that, unlike previous "mixing cell" methods, uses a variable number of cells and is independent of gas-oil ratio, volume of the cells, excess oil volumes, and the amount of gas injected. The new method relies entirely on robust P-T flash calculations using any cubic equation-of-state (EOS). We show that mixing cell MMPs are comparable with those of other analytical and experimental methods, and that our mixing cell method finds all the key tie lines predicted by MOC; however, the method proved to be more robust and reliable than current analytical methods. Second, we identify a number of problems with analytical methods of MMP estimation, and demonstrate them using real oil characterization examples. We show that the current MOC results, which assume that shocks exist from one key tie line to the next may not be reliable and may lead to large errors in MMP estimation. In such cases, the key tie lines determined using the MOC method do not control miscibility, likely as a result of the onset of L₁-L₂-V behavior. We explain the problem with a simplified pseudo-ternary model and offer a procedure for determining when an error exists and for improving the results. Finally, we present a simple mathematical model for predicting the MMP of contaminated gas. Injection-gas compositions often vary during the life of a gasflood because of reinjection and mixing of fluids in situ. Determining the MMP by slim-tube or other methods for each possible variation in the gas-mixture composition is impractical. Our method gives an easy and accurate way to determine impure CO₂ MMPs for variable field solvent compositions on the basis of just a few MMPs. Alternatively, the approach could be used to estimate the enrichment level required to lower the MMP to a desired pressure. / text

Während der Elbeflut im Juni 2013 wurde in Dresden erstmals eine über das Internet frei zugängliche Hochwasserkarte eingesetzt. Über 3 Millionen Zugriffe erfolgten innerhalb des einwöchigen Betriebes. Somit konnte ein großer Teil der Einwohner erreicht und über aktuelle Gefahren informiert werden. Mit den Möglichkeiten, die eine solche Plattform bietet, wird aber gleichzeitig auch die Frage aufgeworfen, wie sich Bürger in Zukunft besser koordinieren lassen. (...)

Non-point pollution from stormwater runoff is one of the greatest threats to water quality in the United States today, particularly in urban karst settings. In these settings, the use of karst features and injection wells for stormwater management results in virtually untreated water being directed into the karst aquifer. Currently, no policies exist specifically to provide water quality protections to karst environments. This study utilized a combination of karst stormwater quality data, along with survey data collected from MS4 Phase II communities, and an analysis of current federal, local, and state water quality regulations, to assess the need for karst-specific water quality regulations. Water quality data indicate that significant levels of contamination are mobilized during storm events, and often are directed into the karst system via Class V injection wells. Survey data collected from MS4 stakeholders in the karst regions of Kentucky indicate stakeholders are generally unable to explain local karst regulations or the steps taken to develop them. This confusion comes in part from insufficient progress on evaluation criteria available for the MS4 Minimum Control Measures (MCMs). Karst waters are often placed into the legal “gray zone” due in part to differences in definitions of key terms in state and federal regulations. This study recommends the development of regulations specific to karst waters at the state and federal levels through either the adaptation of existing or creation of new policies, which place an emphasis on the integration of water quality monitoring and karst education.

Lakes resulting from open pit mining may be potential water resources or potential environmental problems, depending on their water quality. As the global abundance of pit mines and pit lakes increases, there is increasing pressure on the mining industry to create pit lakes that have environmental, social, and/or economical utility. This thesis uses an interdisciplinary approach involving mineralogy, physical limnology, and geochemistry to predict and improve the water quality of a proposed pit lake at the Martha gold mine, New Zealand. A mineral quantification method developed for this study measured the distributions and concentrations of wall rock minerals, and identified 8 relatively homogeneous wall rock regions, called mineral associations. Acid-base accounting using calcite and pyrite quantities identified 3 associations with acid-generating potential. Three physical limnology tools (relative depth, wedderburn number, and numerical modeling with DYRESM), predicted that the upper 2/3 of the lake will circulate annually during the winter turnover period, whereas the lower 1/3 will remain permanently isolated. Permanent stratification resulted from density differences between groundwater and river water inputs during lake filling, plus lake morphology. The geochemical model used the distribution of mineral associations to characterize the composition of pit wall runoff, and used the limnologic prediction to define the mixing frequency, mixing depth, and layer volumes. Initial modeling with the geochemical program PHREEQC indicated the lake will have a pH of 5, and Cu and Zn concentrations that exceed aquatic life protection guidelines. Sensitivity analyses showed that subaqueous water-rock reactions did not have a significant affect on lake pH, suggesting these reactions are less important geochemical factors in pyrite-bearing pit lakes. Surface adsorption onto ferrihydrite reduced concentrations of As, Pb, and Cu, suggesting these reactions are important geochemical factors in pit lakes. By covering the acid-generating mineral associations, lake pH increased above 6.5, allowing for future recreational use. Concentrations of Cu complied with aquatic life protection guidelines, however, Zn concentrations remained above these guidelines. This study demonstrates the value of interdisciplinary pit lake predictions in the design of closure plans for open pit mines. Such studies improve the ability of mining companies to sustainably develop mineral resources.

Lakes resulting from open pit mining may be potential water resources or potential environmental problems, depending on their water quality. As the global abundance of pit mines and pit lakes increases, there is increasing pressure on the mining industry to create pit lakes that have environmental, social, and/or economical utility. This thesis uses an interdisciplinary approach involving mineralogy, physical limnology, and geochemistry to predict and improve the water quality of a proposed pit lake at the Martha gold mine, New Zealand. A mineral quantification method developed for this study measured the distributions and concentrations of wall rock minerals, and identified 8 relatively homogeneous wall rock regions, called mineral associations. Acid-base accounting using calcite and pyrite quantities identified 3 associations with acid-generating potential. Three physical limnology tools (relative depth, wedderburn number, and numerical modeling with DYRESM), predicted that the upper 2/3 of the lake will circulate annually during the winter turnover period, whereas the lower 1/3 will remain permanently isolated. Permanent stratification resulted from density differences between groundwater and river water inputs during lake filling, plus lake morphology. The geochemical model used the distribution of mineral associations to characterize the composition of pit wall runoff, and used the limnologic prediction to define the mixing frequency, mixing depth, and layer volumes. Initial modeling with the geochemical program PHREEQC indicated the lake will have a pH of 5, and Cu and Zn concentrations that exceed aquatic life protection guidelines. Sensitivity analyses showed that subaqueous water-rock reactions did not have a significant affect on lake pH, suggesting these reactions are less important geochemical factors in pyrite-bearing pit lakes. Surface adsorption onto ferrihydrite reduced concentrations of As, Pb, and Cu, suggesting these reactions are important geochemical factors in pit lakes. By covering the acid-generating mineral associations, lake pH increased above 6.5, allowing for future recreational use. Concentrations of Cu complied with aquatic life protection guidelines, however, Zn concentrations remained above these guidelines. This study demonstrates the value of interdisciplinary pit lake predictions in the design of closure plans for open pit mines. Such studies improve the ability of mining companies to sustainably develop mineral resources.

Lakes resulting from open pit mining may be potential water resources or potential environmental problems, depending on their water quality. As the global abundance of pit mines and pit lakes increases, there is increasing pressure on the mining industry to create pit lakes that have environmental, social, and/or economical utility. This thesis uses an interdisciplinary approach involving mineralogy, physical limnology, and geochemistry to predict and improve the water quality of a proposed pit lake at the Martha gold mine, New Zealand. A mineral quantification method developed for this study measured the distributions and concentrations of wall rock minerals, and identified 8 relatively homogeneous wall rock regions, called mineral associations. Acid-base accounting using calcite and pyrite quantities identified 3 associations with acid-generating potential. Three physical limnology tools (relative depth, wedderburn number, and numerical modeling with DYRESM), predicted that the upper 2/3 of the lake will circulate annually during the winter turnover period, whereas the lower 1/3 will remain permanently isolated. Permanent stratification resulted from density differences between groundwater and river water inputs during lake filling, plus lake morphology. The geochemical model used the distribution of mineral associations to characterize the composition of pit wall runoff, and used the limnologic prediction to define the mixing frequency, mixing depth, and layer volumes. Initial modeling with the geochemical program PHREEQC indicated the lake will have a pH of 5, and Cu and Zn concentrations that exceed aquatic life protection guidelines. Sensitivity analyses showed that subaqueous water-rock reactions did not have a significant affect on lake pH, suggesting these reactions are less important geochemical factors in pyrite-bearing pit lakes. Surface adsorption onto ferrihydrite reduced concentrations of As, Pb, and Cu, suggesting these reactions are important geochemical factors in pit lakes. By covering the acid-generating mineral associations, lake pH increased above 6.5, allowing for future recreational use. Concentrations of Cu complied with aquatic life protection guidelines, however, Zn concentrations remained above these guidelines. This study demonstrates the value of interdisciplinary pit lake predictions in the design of closure plans for open pit mines. Such studies improve the ability of mining companies to sustainably develop mineral resources.