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Phase behavior describes the complex interaction between physically distinct, separable portions of matter called phases that are in contact with each other. Typical phases are solids, liquids and vapors. Thermodynamics, which is central to understanding phase behavior, is the study of energy and its transformations. Using thermodynamics, we can follow the energy changes that occur during phase changes and predict the outcome of a process. Thermodynamics began as the study of heat applied to steam power but was substantially broadened by Gibbs in the middle to late 1800s.
- Information Technology > Knowledge Management (0.41)
- Information Technology > Communications > Collaboration (0.41)
The interaction of the different molecules in a mixture causes behavior not observed inpure fluids. Phase diagrams describe the volumetric behavior of mixtures. This article presents the basic procedure to predict the equilibrium phase behavior of mixtures by a cubicequation of state (EOS). More detailed information can be found in many sources, including Firoozabadi[1] and Whitson and Brule.[2] The thermodynamic properties of a mixture can be calculated with the same EOS for a pure fluid, with some modifications. The primary difference is that the mixture molar volume for a phase is calculated with EOS constants and temperature-dependent functions of the phase molar composition, eitherxi or yi.
- Information Technology > Knowledge Management (0.41)
- Information Technology > Communications > Collaboration (0.41)
Abstract This work is based on theoretical studies and/or experimental observations carried out diverse authors whom have investigated on the "foamy oil phenomenon" developing a methodology to characterize these crude oils thermodynamically, taking as bases nonconventional PVT analysis and using as research tool the application of equations of state and methods known for the determination of the equilibrium constants liquid-gas. It is presented two new correlations developed in this work for the calculation of the viscosity of heavy crude oils, which are based on values of molar fractions of liquid and gas in equilibrium. The proposed methodology was validated using conventional and nonconventional PVT data of wells located in the Orinoco Belt, Jobo Field, Morichal Area obtaining excellent results and showing that the proposed methodology is applicable to conventional and nonconventional heavy crude oils in all the possible scenes, that is to say, whether necessary information is available. Introduction When we analyse foamy crude oils under the optics of primary production mechanisms known traditionally, have not been able to explain with exactitude the production behavior in these reservoirs; this has given basis to many people to do research with the objective of explainning the origin of this atypical behavior. To such extreme to establishment the theory of "foamy oil phenomenon", which considers a transient state or supersaturation condition, in which take place the characteristics named "atypical" that identify to this type of heavy crude oils. It's of extreme importance for the petroleum industry to model the thermodynamic behavior of foamy oils reservoirs, since a good characterization fluid increases the probabilities to obtain better numerical reservoir simulations of and thus to be able to consider with most exactitude the total recovery. Characterization of Foamy Oils The foamy oil phenomenon has appeared only in heavy and extra-heavy crude oils, since in these crudes the viscous forces surpass to the gravitational forces on the productive life of reservoirs, reason why this phenomenon goberns the production behavior of these reservoirs. This phenomenon to appear after that reservoir pressure reaches the bubble point pressure, from this pressure the petroleum production increases, the gas bubbles expand to displace petroleum towards wells quickly. Depending of pressure and extraction rate of wells placed in the reservoir is possible that gas bubbles be produced with the oil. With the purpose to characterize the ability that have some heavy crudes to show the foamy oil behavior and entrap gas that is released by each decrease of pressure. Nonconventional PVT analysis were developed which defer from the method used traditionally. The conceptual difference between this analysis and the method used conventionally, is that the flash and differential liberation tests are carried out without agitation of the cell. Generally, the results obtained by means of conventional and nonconventional PVT analysis differ remarkably mainly in the values of bubble point pressure obtained by both methods for foamy oils. Frequently values of bubble point pressure smaller are obtained in nonconventional PVT analysis because occurs entrapping of gas within the oleic phase of the crude reason why it's deduced that supersaturation phenomenon occurs, the gas bubbles released to pressure far below the bubble point pressure are dissolved and/or dispersed within the phase of petroleum in a perfect hydrodynamic equilibrium. It later on that such hydrodynamic equilibrium should be broken to obtain free gas. It had been determinate by laboratory experiences that viscosity of foamy crude oils obtained using capillary viscometers are more suitable to make reservoir numerical simulations than those obtained with rotational viscometers, in this case, strench caused by shaking the crude sample breaks the dispersion gas/oil and release bubble gas to build a free gas cap separated of the crude oil.
- North America > United States (1.00)
- South America > Venezuela > Anzoรกtegui (0.29)
- South America > Venezuela > Orinoco Oil Belt (0.25)
- South America > Venezuela > Jobo Field (0.99)
- South America > Venezuela > Eastern Venezuela Basin > Hamaca Area > Bare Field (0.99)
- South America > Venezuela > Anzoรกtegui > Eastern Venezuela Basin > Maturin Basin > Hamaca Area (0.99)
- South America > Venezuela > Anzoรกtegui > Eastern Venezuela Basin > Maturin Basin > Cerro Negro Area Field (0.99)
Abstract Hydrocarbon phase behaviour must be rigorously represented when there is a need to properly account for mass transfer between phases in a porous medium. The overly simplified black-oil formulation, although appropriate for primary depletion and waterflooding, provides inadequate representation of miscible displacement processes. As a result, compositional simulation has evolved to provide thermodynamically consistent means to accurately describe the phases and compositions present within the porous reservoir rocks. Compositional simulators have become essential modelling tools for CO2 processes in the Petroleum Industry. Advances in computational power have encouraged the development of meaningful improvements and refinements that were not possible until very recently. CO2 injection into an oil reservoir at low temperatures causes the appearance of a three-phase hydrocarbon thermodynamic Liquid-Liquid-Vapour (LLV) equilibrium. The traditional use of a two-phase flash calculation in this three-phase region may lead to instability problems. Besides, commercial compositional simulators normally do not consider two-phase hydrocarbon Liquid-Liquid (LL) thermodynamic equilibrium that appears in oil reservoirs at low temperatures in the presence of CO2. Instead, it is treated as a Liquid-Vapour (LV) thermodynamic equilibrium and the fluid flux behaviour is not well represented. A compositional simulator must be able to represent adequately the LL hydrocarbon thermodynamic equilibrium when it is present in order to rigorously model the reservoir phase behaviour in the presence of CO2. A novel procedure has been developed to overcome instabilities which may arise in calculation of multiphase liquid-liquid-vapour (LLV) hydrocarbon phase equilibrium. In addition, a new procedure has been developed for representing the thermodynamic liquid-liquid hydrocarbon equilibrium in a compositional simulator. This new procedure represents the real behaviour of the fluid flux. It is more rigorous than the traditional approach of lumping of the two liquid phases into a pseudo single liquid phase or as a liquid-vapour (LV) thermodynamic equilibrium. The results of this implementation are presented and analyzed in detail.
- North America > United States > Texas > Permian Basin > Central Basin > Wasson Field > Wolfcamp Formation (0.99)
- North America > United States > Texas > Permian Basin > Central Basin > Wasson Field > Wichita Albany Formation (0.99)
Abstract The modeling of miscible displacement processes in petroleum reservoirs, such as Carbon Dioxide Injection or Enriched Gas Drive, has been traditionally done with compositional simulators in which the distribution of the different components or pseudocomponents among the phases is given by equilibrium constants which are determined with a suitable Equation of State, or given as input to the simulator in the form of tables or correlations as function of pressure, temperature and composition. In other words, the partial differential equations describing the flow of each phase through the reservoir are solved by finite difference techniques assuming thermodynamic equilibrium among the phases in each grid block, every time step. It is shown here that this assumption leads to large errors since at typical conditions interphase mass transfer resistances are large and thermodynamic equilibrium in not nearly reached during the time steps of interest. In this work, a one dimensional compositional simulator is developed where mass transfer kinetics is taken into account by including equations which describe the interfacial molar flow of each component in terms of overall mass transfer coefficients, and the difference between the actual phase concentration and that it would have at equilibrium. Sensitivity studies are carried out to determine mass transfer resistance contributions to process performance. The simulator was validated by modeling CO2 displacement experiments carried out in a laboratory slim tube. In this case, the relative permeability curves were kept constant, and the overall mass transfer coefficient was changed to reproduce the oil production of the experiments. The experimental results were also simulated with a conventional compositional simulator, changing the relative permeability curves to adjust oil production.