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Browsing by Author "Baù, Domenico, advisor"

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    Methodologies to detect leakages from geological carbon storage sites
    (Colorado State University. Libraries, 2014) González-Nicolás Álvarez, Ana, author; Baù, Domenico, advisor; Fontane, Darrell, committee member; Ronayne, Michael, committee member; Sale, Thomas, committee member
    Geological carbon storage (GCS) has been proposed as a favorable technology to reduce carbon dioxide (CO2) emissions to the atmosphere. Candidate storage formations include abandoned oil and natural gas reservoirs, un-mineable coal seams, and deep saline aquifers. The large global storage capacity and widespread occurrence of deep saline formations make them ideal repositories of large volumes of CO2, however they generally lack of data for geological characterization in comparison to oil and gas reservoirs. Thus, properties of the injected formation or the sealing formation are unknown, which implies that the evolution and movement of the CO2 plume are uncertain in these geological formations. The first part of this research aims to provide an understanding of the main sources of uncertainty during the injection of CO2 that cause leakage variability and fluid pressure change near the injection well, which could be responsible for fracturing the sealing formation. With this purpose the effect of uncertain parameters such as permeability and porosity of injected aquifer, permeability of CO2 leakage pathways through the sealing layers, system compressibility, and brine residual saturation are investigated using stochastic and global sensitivity analyses. These analyses are applied to a potential candidate site for GCS located at the Michigan Basin. Results show aquifer permeability and system compressibility are the most influential parameters on fluid overpressure and CO2 mass leakage. Other parameters, such as rock porosity, permeability of passive wells, and brine residual saturation do not influence fluid overpressure nearby the injection well. CO2 mass leakage is found to be sensitive to passive well permeability as well as the type of statistical distribution applied to describe well permeability. Scarce data of the Michigan Basin exist that can be used directly to describe the spatial distribution at the basin scale of the caprock overlying the candidate site. The continuity of this formation is uncertain. The second part of this investigation explores the application of binary permeability fields for the study of CO2 leakage from GCS at the candidate site. A sequential indicator simulation algorithm is used to populate binary permeability fields representing a caprock formation with potential leaky areas (or inclusions). Results of the caprock continuity uncertainty conclude that increasing the probability of inclusions occurrence increases the CO2 leakage. In addition, the correlation length used by the sequential indicator simulator affects the occurrence of inclusions. The third part investigates the detection and location of the presence of possible brine or carbon leakage pathways at the caprock during the injection operations of a GCS system. A computational framework for the assimilation of changes in head pressure data into a subsurface flow model is created to study the evolution of the CO2 plume and brine movement. The capabilities of two data assimilation algorithms, the ensemble smoother (ES) and the ensemble Kalman smoother (EnKS), to identify and locate the leaky pathways are examined. Results suggest that the EnKS is more effective than the ES in characterizing caprock discontinuities.
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    Semi-analytical tool for optimal management of alluvial aquifers hydraulically connected to streams
    (Colorado State University. Libraries, 2013) Hassan, Azzah Salah El-Din, author; Baù, Domenico, advisor; Grigg, Neil S., committee member; Ronayne, Michael J., committee member
    Conjunctive water resources use is becoming an important tool in water management, especially with the increase in demands in all life sectors, and the decrease in available water resources with all the evolving obstacles of climate change, growing populations in addition to the conflicts over water resources in some areas of the world. A groundwater/surface water conjunctive management problem of a hydraulically connected aquifer/stream system is addressed in this research under the prior appropriation doctrine of water allocation practiced in the western states of the USA including Colorado. One approach for applying the concept of conjunctive groundwater/surface water management is achieved by techniques of artificial recharge of aquifers, where water is injected and stored in aquifers when surface water surplus is available for that purpose and pumped in the future when there is a need. Within the prior allocation doctrine, groundwater users in Colorado historically started extracting water from the aquifers underlying their agricultural lands after surface water rights were fully allocated. Consequently, in a system of hydraulically connected aquifers and streams as in the South Platte River Basin, ground water users are junior water right holders, who are allowed to divert surface water only when all senior water right holders have had their full allocation. From this perspective, the objective of the groundwater management problem is to minimize the impact of artificial recharge injection and extraction operations on the stream connected to the targeted aquifer, meaning, when extracting water from the aquifer, the pumped amount should be equal to the injected volumes, else wise the aquifer will compensate for the difference by depleting the stream. An important effect characterizing artificial recharge and groundwater pumping is the change in aquifer head levels during operations, as excessive injection might cause water mounds and over pumping might result in a stressed aquifer. In this study, groundwater pumping and artificial recharge effects on aquifers are simulated using the semi-analytical models describing the effect of an operating well in the aquifer and the interconnected stream. These models are derived from the formulated analytical solutions for aquifer drawdown and stream depletion obtained by Theis (1935) and Glover and Balmer (1945) In the first part of this research, a number of semi-analytical models are derived and implemented in MATLAB codes to simulate the response of both the aquifer and the stream to cyclically operating wells. These models can handle the cases of laterally infinite aquifers, semi-infinite aquifers limited by a stream or an impermeable boundary, and finite aquifer comprised between an impermeable boundary and a stream or between two streams. In the second part of the research, these models are used to solve a groundwater management problem that seeks to minimize the absolute value of the volume of stream depletion/accretion over a given time period while meeting prescribed constraints on aquifer water levels, irrigation demands and injection water availability. This problem is tackled using linear programming algorithms, which is proven to be effective in providing first-hand estimations of optimal injection-extraction schemes for the management of systems characterized by large numbers of operating wells, within a reasonably small computation time.