A model for real -time control of a multipurpose reservoir under the conditions of uncertainty is developed. The control model is formulated as a multistage decision process. It is conceptualized in the form of two sub -processes. The first level process is a Forecast - Strategy Process which performs as an open-loop feedback controller. It is defined by a sequence of forecasts and optimal release strategies against these forecasts. At each forecast time (time of issuing the forecast), the optimal release strategy is computed for the time period equal to the lead time of the forecast, and it remains in execution until the next forecast time. The second level process, defined for each forecast time, is a Control Process which for the given forecast generates the release strategy satisfying the preference criterion (minimization of expected disutility). This process is formulated as a truncated Markovian adaptive controller performing on a finite set of discrete times --the same set which indexes the forecast inflow process. To evaluate the past performance of the control, a set of measures of effectiveness is proposed. Computational aspects of the control model are analyzed. Structural properties of the reservoir control process are explored in the main theorem which assures the monotonicity of the optimal strategy with respect to one of the state variables. Also, the properties of the optimal strategy for the case of a categorical forecast are proven. Next, two suboptimal strategies are derived: (1) partial open -loop strategy and (2) naive /partial open-loop strategy. Finally, a'discretization procedure which guarantees convergence of the numerical solution is discussed, and the computational requirements of the optimal and two suboptimal strategies are compared.

From the standpoint of real -time reservoir operation, the multipurpose control problem may be reduced to a dual purpose problem of (1) flood control under uncertain inflow and (2) conservation control (water supply, power generation, low flow augmentation, recreation, etc.) after the flood has receded. A preference criterion for real -time flood control under the conditions of uncertainty is developed in accordance with three postulates: (1) The input to the control process is a probabilistic forecast of the inflow hydrograph, (2) The control decisions are based upon the decision maker's value judgments concerning preferences over operating attributes, trade -offs between reservóir purposes, and attitude toward risk. (3) The conservation control is imbedded into the flood control through the attribute space of the preference criterion allowing thus for explicit consideration of the trade -offs between reservoir purposes. The preference criterion is developed within the framework of utility theory. The value judgments of the decision maker are quantified in terms of a two -attribute disutility function. It is argued that minimization of expected disutility is a plausible and well motivated criterion for multipurpose real -time reservoir control under uncertainty. A suitable disutility model is developed. The case of a group decision maker is analyzed in depth. Common group utility models based on aggregation of individual utility functions and interpersonal utility comparisons are critically reviewed. An alternative approach based on direct group value judgments is suggested, and a general group utility model for decision -making in engineering systems is developed. The disutility assessment procedures are analysed, and response biases that may be introduced into the decision maker's preference structure by the use of an inappropriate assessment scheme are identified. Some principles and novel techniques for assessing disutility functions are advocated; they are motivated by results of psychological research in human decision behavior, and are further supported by experimental evidence. Results of assessment of the reservoir control disutility function for several single and group decision makers are presented.

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This dissertation contains a discussion concerning the validity of the principle of optimality and the dynamic programming algorithm in the context of discrete time and state multistage decision processes. The multistage decision model developed for the purpose of the investigation is of a general structure, especially as far as the reward function is concerned. The validity of the dynamic programming algorithm as a solution method is investigated and results are obtained for a rather wide class of decision processes. The intimate relationship between the principle and the algorithm is investigated and certain important conclusions are derived. In addition to the theoretical considerations involved in the implementation of the dynamic programming algorithm, some modeling and computational aspects are also investigated. It is demonstrated that the multistage decision model and the dynamic programming algorithm as defined in this study provide a solid framework for handling a wide class of multistage decision processes. The flexibility of the dynamic programming algorithm as a solution procedure for nonroutine reservoir control problems is demonstrated by two examples, one of which is a reliability problem. To the best of the author's knowledge, many of the theoretical derivations presented in this study, especially those concerning the relation between the principle of optimality and the dynamic programming algorithm, are novel.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Bibliography: leaves 222-226. / Ph.D.

Interpretation problems are commonly associated with calculating water saturation in nonhomogenous shaly sand reservoirs. Redefining petrophysical properties based on well logs in shaly sand reservoirs by using fundamental geologic attributes is an important tool in developing subsurface hydrocarbon resources. Studies of the electrical anisotropy of shaly sands have shown that the level of our understanding and our ability to correctly evaluate low resistivity and low contrast pay can be greatly improved. The model developed in this thesis is similar in form to the shaly sand Dual Water model by Clavier et al. (1984). It is an experiment based model designed to directly assess and quantify the mineralogical and electrical effects of clay minerals in heterogeneous reservoirs. Clay minerals usually have multiple effects on petrophysical properties obtained from geophysical well log measurements. The total expansible clay model evaluates these effects via direct measurement of independent mineralogy and conductivity of clay minerals within reservoir sands. This model integrates the following as an effective basis for characterizing shaly sand reservoirs: ??? Rietveld based Siroquant assay for quantitative X-ray diffraction, used in determining mineral percentages from standard XRD trace patterns, ??? Cation exchange capacity, used to determine the quantity of cations involved in the exchange at the shale-water interface, ??? Porosity, permeability, density and resistivity measurements, ??? Thin section petrography, used in identifying mineral patterns, visible porosity and reservoir quality. Overall, application of correlations drawn from the model yields improved results for water saturation which appeared consistent with those earlier calculated using known water saturation models (Clavier et al Dual Water model, 1984, Juhasz, 1981). A total of twenty three samples from two wells in the Cliff Head fIeld were analyzed for this study.

Orientador: Armando Zaupa Remacre / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociencias / Made available in DSpace on 2018-08-09T03:37:21Z (GMT). No. of bitstreams: 1 Sancevero_SergioSacani_D.pdf: 13993022 bytes, checksum: beb2507aee5ca130897dad57c706b2a9 (MD5) Previous issue date: 2007 / Resumo: O processo de caracterização de reservatórios é atualmente uma das etapas mais importantes na exploração, desenvolvimento e produção de um campo. Porém, para que esse processo seja realizado da melhor forma possível é preciso se ter o conhecimento de determinados métodos, que integram as diferentes informações disponíveis. Desse modo, o objetivo principal dessa tese é estudar de forma criteriosa e quantitativa o processo de caracterização de reservatórios do ponto de vista dos dados sísmicos, avaliando antigos e novos métodos, e definindo novas metodologias que possam ser aplicadas de maneira decisiva neste processo. Para que esses métodos pudessem ser avaliados de maneira conclusiva foi utilizado nesta tese um modelo sintético que reproduzisse minimamente algumas características cruciais de determinados reservatórios como a complexa distribuição dos corpos de areia e a presença de corpos com espessura subsísmica que levassem ao limite as técnicas de modelagem tradicionais, proporcionando avaliar novos métodos. Assim, para caracterizar essas complexas feições, foram utilizados nesta tese dois meios principais de interpretação, primeiro a inversão sísmica dando um caráter preditivo ao dado sísmico e por fim a análise multiatributos, dando um caráter classificatório. No caso da inversão sísmica foram utilizados três métodos de obtenção da impedância acústica. Entre eles, foi a inversão geoestatística que demonstrou ser a mais eficiente das técnicas no que diz respeito à caracterização de reservatórios com espessura subsísmica e complexa distribuição dos corpos de areia. No caso dos atributos, pôde-se demonstrar que é necessário que sejam tratados com uma abordagem multivariada para que seja aproveitada a correlação entre eles e que por meio de técnicas de classificação e modelagem possa se decidir os mais relevantes para o processo. Neste caso 3 métodos de análise multivariada foram apresentados e testados, sendo que dois deles (ICA e MAF) de maneira inédita e que produziram resultados superiores àqueles alcançados quando a tradicional técnica de PCA é aplicada. Assim, com o que foi apresentado, pode-se concluir que o processo de caracterização é um estágio crucial para o desenvolvimento dos campos, mas não é fácil de ser realizado, a menos que os métodos e as técnicas envolvidas sejam conhecidas de maneira profunda. Só assim, é possível extrair o máximo de informações do dado sísmico, caracterizando o reservatório de forma quantitativa e integrada, otimizando sua produção e reduzindo os riscos e custos com a sua explotação / Abstract: The reservoir characterization process can be considered curretly the most important stage in the exploration, development and production of the oil field. However, this process is only carried out in the best way if the geologists, geophisicist and engineering has the knowledge of some definitive methods and techniques that integrated all information available about the field. Thus, the aim of this thesis is to study in a criterious and quantitative way the reservoirscharacterization process, analyzing the seismic data,by the evaluation of classic and novel methods, to defining new methodlogies that can be applied in decisive way into this process. So, for these methods could be evaluated in a conclusive way, were used in this thesis asynthetic reference model that reproduced some critical features of determined reservoirs, as the complex distribution of sand bodies and the subseismic thickness. These characteristics pushing to the limit the traditional modelling techniques. In this thesis to characterizze the complex features present in the reference model we used two interpretation techniques, first we analyze the seismic inversion that give a preditive character to the seismic data and after we study the multiattribute analysis that give a classificatory caracter to the seismic interpretation. For the seismic inversion, the stochastic or geostatistical inversion, that demonstrated to be the most efficient technique to characterized the complex and the subseismic features present in the model. About the seismic attributes it could be demonstrated that even so in some cases they represent the features of the model, are necessary that they are dealt with a multivariate approach, to used the advantage of the correlation between them. For the seismic attribute analysis, 3 methods of multivariate statistics analysis were used, two of them (ICA and MAF) for the first time in the reservoir characterization processo With the results we can proved that these 2 new methods improved the process of multiattribute anlysis prducing superior results when compare with the results obtained by the application of traditional PCA technique. With it was presented, can be concluded that the reservoir characterization process is a crucial stage and have some difficults to be accomplishment, unless the methods and the involved techniques are known deeply. Thus it is possible to extract the maximum informations from the datasets, characterizing the reservoir in a quantitative and integrated environmental, optimizing its production and reducing the risks and the costs with its explotation / Doutorado / Administração e Politica de Recursos Minerais / Doutor em Ciências

This dissertation contains a discussion concerning the validity of the principle of optimality and the dynamic programming algorithm in the context of discrete time and state multistage decision processes. The multistage decision model developed for the purpose of the investigation is of a general structure, especially as far as the reward function is concerned. The validity of the dynamic programming algorithm as a solution method is investigated and results are obtained for a rather wide class of decision processes. The intimate relationship between the principle and the algorithm is investigated and certain important conclusions are derived. In addition to the theoretical considerations involved in the implementation of the dynamic programming algorithm, some modeling and computational aspects are also investigated. It is demonstrated that the multistage decision model and the dynamic programming algorithm as defined in this study provide a solid framework for handling a wide class of multistage decision processes. The flexibility of the dynamic programming algorithm as a solution procedure for nonroutine reservoir control problems is demonstrated by two examples, one of which is a reliability problem. To the best of the author's knowledge, many of the theoretical derivations presented in this study, especially those concerning the relation between the principle of optimality and the dynamic programming algorithm, are novel.

The onset of summer stratification in temperate lakes and reservoirs forces a decoupling of the hypolimnion from the epilimnion that is sustained by strong density gradients in the metalimnion. These strong gradients act as a barrier to the vertical transport of mass and scalars leading to bottom anoxia and subsequent nutrient release from the sediments. The stratification is intermittently overcome by turbulent mixing events that redistribute mass, heat, dissolved parameters and particulates in the vertical. The redistribution of ecological parameters then exerts some control over the ecological response of the lake. This dissertation is focused on the physics of deep vertical mixing that occurs beneath the well-mixed surface layer in stratified lakes and reservoirs. The overall aim is to improve the ability of numerical models to reproduce deep vertical mixing, thus providing better tools for water quality prediction and management. In the first part of this research the framework of a one-dimensional mixed-layer hydrodynamic model was used to construct a pseudo two-dimensional model that computes vertical fluxes generated by deep mixing processes. The parameterisations developed for the model were based on the relationship found between lake-wide vertical buoyancy flux and the first-order internal wave response of the lake to surface wind forcing. The ability of the model to reproduce the observed thermal structure in a range of lakes and reservoirs was greatly improved by incorporating an explicit turbulent benthic boundary layer routine. Although laterally-integrated models reproduce the net effect of turbulent mixing in a vertical sense, they fail to resolve the transient distribution of turbulent mixing events triggered by local flow properties defined at far smaller scales. Importantly, the distribution of events may promote tertiary motions and ecological niches. In the second part of the study a large body of microstructure data collected in Lake Kinneret, Israel, was used to show that the nature of turbulent mixing events varied considerably between the epilimnion, metalimnion, hypolimnion and benthic boundary layer, yet the turbulent scales of the events and the buoyancy flux they produced collapsed into functions of the local gradient Richardson number. It was found that the most intense events in the metalimnion were triggered by high-frequency waves generated near the surface that grew and imparted a strain on the metalimnion density field, which led to secondary instabilities with low gradient Richardson numbers. The microstructure observations suggest that the local gradient Richardson number could be used to parameterise vertical mixing in coarse-grid numerical models of lakes and reservoirs. However, any effort to incorporate such parameterisations becomes meaningless without measures to reduce numerical diffusion, which often dominates over parameterised physical mixing. As a third part of the research, an explicit filtering tool was developed to negate numerical diffusion in a threedimensional hydrodynamic model. The adaptive filter ensured that temperature gradients in the metalimnion remained within bounds of the measured values and so the computation preserved the spectrum of internal wave motions that trigger diapycnal mixing events in the deeper reaches of a lake. The results showed that the ratio of physical to numerical diffusion is dictated by the character of the dominant internal wave motions.

Hydrocarbon reserves are generally produced through wells drilled into reservoir pay zones. During production, gas liberation from the oil phase occurs due to pressure decline in the wellbore. Thus, we expect multiphase flow in some sections of the wellbore. As a multi-phase/multi-component gas-oil mixture flows from the reservoir to the surface, pressure, temperature, composition, and liquid holdup distributions are interrelated. Modeling these multiphase flow parameters is important to design production strategies such as artificial lift procedures. A wellbore fluid flow model can also be used for pressure transient test analysis and interpretation. Considering heat exchange in the wellbore is important to compute fluid flow parameters accurately. Modeling multiphase fluid flow in the wellbore becomes more complicated due to heat transfer between the wellbore fluids and the surrounding formations. Due to mass, momentum, and energy exchange between the wellbore and the reservoir, the wellbore model should be coupled with a numerical reservoir model to simulate fluid flow accurately. This model should be non-isothermal to consider the effect of temperature. Our research shows that, in some cases, ignoring compositional effects may lead to errors in pressure profile prediction for the wellbore. Nearly all multiphase wellbore simulations are currently performed using the "black oil" approach. The primary objective of this study was to develop a non-isothermal wellbore simulator to model transient fluid flow and temperature and couple the model to a reservoir simulator called General Purpose Adaptive Simulator (GPAS). The coupled wellbore/reservoir simulator can be applied to steady state problems, such as production from, or injection to a reservoir as well as during transient phenomena such as well tests to accurately model wellbore effects. Fluid flow in the wellbore may be modeled either using the blackoil approach or the compositional approach, as required by the complexity of the fluids. The simulation results of the new model were compared with field data for pressure gradients and temperature distribution obtained from wireline conveyed pressure recorder and acoustic fluid level measurements for a gas/oil producer well during a buildup test. The model results are in good agreement with the field data. Our simulator gave us further insights into the wellbore dynamics that occur during transient problems such as phase segregation and counter-current multiphase flow. We show that neglecting these multiphase flow dynamics would lead to unreliable results in well testing analysis.