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Stochastic computer simulations of viscous fingeringRees, S. January 1987 (has links)
This thesis aims to develop a computer simulation of the process that occurs when one displaces a viscous fluid such as oil by a less viscous one such as water in a porous medium. Chapter 1 outlines the problem and explains why a computer simulation rather than analytical treatment is necessary for the problem. Previous computer simulations of the problem are reviewed and their respective advantages and disadvantages are considered. Chapter 2 introduces the concept of 'simulated annealing', a stochastic computational technique for solving minimisation problems with many variables and this technique is used to make a crude model of the displacement problem. The results from this are considered and the reasons for the model's failure to adequately solve the problem are discussed. In chapter 3, simulated annealing is applied to the simpler problem of the travelling salesman where one has to find the shortest route around a collection of points. The aim of this chapter is to try and find an optimum simulated annealing schedule to minimise the computer time needed to achieve a satisfactory solution. This is successfully accomplished for this particular problem by fitting the relaxation time of the system as a function of temperature to an Arrhenhius type law. But this optimisation is problem specific and it is concluded that the complicated nature of the oil displacement problem effectively precludes treatment by annealing. In chapter 4 a stochastic micro model is developed in which a pressure gradient across the system forces water into oil bearing pores. The pores have varying sizes which represent sizes which represent the varying permeability in a porous medium. A modified Gauss Seidel method is used to solve for the pressure field and an analytic expression for the saturation update is developed. The final chapter, chapter 5, develops the above model further and in particular develops a scheme whereby conservation of fluid is guaranteed. The profiles of the fingering of the water into the oil are studied and it is found that their interface fractal dimension varies monotonically with viscosity ratio.
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Two phase flows in disordered systemsOlive, A. January 1984 (has links)
No description available.
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M.R.I. studies of fluid flow distribution in macroscopic glass bead packsBencsik, Martin January 1998 (has links)
No description available.
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Higher order Godunov IMPES compositional modelling of oil reservoirsMorton, Alison January 1996 (has links)
No description available.
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Experimental studies on resistance to fluid displacement in single poresKwelle, Stephen Okachukwu January 2017 (has links)
Understanding the resistance to displacement of one fluid by another in multiphase transport in a porous medium is very beneficial in hydrocarbon exploration and production as well as geological storage of carbon dioxide. Pore resistance behaviour of a porous medium controls the fluxes of fluids through the caprocks over the geological times and therefore directly determines the volume and localization of the hydrocarbons trapped (best locations for exploration) and also the overpressured formation (zone of drilling hazard). In the design for enhanced oil recovery and geological storage, it sets a limit on both the injection pressure and storage capacity of the reservoir to avoid an upward migration of the injected fluid into the overlaying formations. Many investigations have been carried out on the resistance to porous media flows for decades, yet the understanding of the individual factors affecting it is not complete, because most studies were carried out on core samples, whereas flow resistance depends on the flow details at the pore scale. For example, two core samples may have same porosity but different pore size. This research focused on advancing the understanding of resistance to multiphase displacement in a porous medium, using the pressure profile of interface flow through single pores, to measure the resistance to two-phase flow and then link the impact of pore geometry, surface tension, fluid properties, and wettability, on the pressure profile to the displacement process, in order to fill the noticed gap of knowledge. Experiments conducted in this research using tapered capillaries revealed that the resistance to two-phase flow is significantly higher than the single phase resistance and the pore throat of a porous medium is not just determined by a group of smallest pore sizes as understood using core samples, but by response of critical effective pore diameter to resistance to two-phase interface flow. The initiation of a pore throat is characterised by a drastic increase in the resistant pressure at the effective pore size. The effective pore diameter is generally less than 500 μm and increases with the pore tip diameter and the capillary gradient, interfacial tension, but decreased by surfactants. Viscosity does not have any significant effect on the effective pore diameter. The study also revealed a relationship between pore contact angle and pore throat; pore contact angle is maximum and remains fairly constant at the pore throat. The overall outcome of this research is a significant contribution to the influence of pore geometry on the resistance to porous media flows.
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[pt] DESLOCAMENTO DE FLUIDOS COMPLEXOS EM ESPAÇOS ANULARES IRREGULARES / [en] DISPLACEMENT OF COMPLEX FLUIDS IN IRREGULAR ANNULAR SPACESPEDRO JOSE TOBAR ESPINOZA 30 November 2021 (has links)
[pt] O deslocamento de um líquido por outro em espaços anulares é comumente
encontrado na indústria do petróleo, e a maioria deles envolve materiais
não newtonianos. O espaço anular muitas vezes apresenta irregularidades
causadas pela erosão, onde quantidades consideráveis de fluido de perfuração
podem ser deixadas para trás durante o processo de deslocamento,
comprometendo a qualidade da operação de cimentação. Motivados por
esse processo industrial, testes de deslocamento entre líquidos a vazão
constante foram realizados em espaços anulares cuja parede externa possui,
em uma determinada posição axial, um aumento repentino de diâmetro
seguido de uma diminuição repentina de diâmetro mais a jusante. O objetivo
dos experimentos era determinar a eficiência do deslocamento em função
da vazão, reologia dos fluidos e geometria da cavidade. Os resultados
revelaram forte influência desses parâmetros na eficiência de deslocamento.
Ao mesmo tempo, um estudo numérico foi desenvolvido. Simulações
numéricas das equações de Navier-Stokes em geometria axissimétrica para
fluidos incompressíveis foram acopladas ao método Level-Set para captura
da interface. Fluidos com viscosidade constante e o modelo newtoniano
generalizado com função viscosidade de Carreau-Yasuda foram utilizados.
Isso permitiu simular deslocamentos entre dois fluidos newtonianos e entre
um fluido newtoniano e outro não-newtoniano. Este foi utilizado tanto como
fluido deslocador quanto como deslocado. Foram realizadas simulações para
várias razões de diâmetros, viscosidades, tempos de relaxação, e números de
capilaridade e de Reynolds. Identificamos quando a aproximação do espaço
anular por duas placas paralelas pode ser aplicada e calculamos como a
forma da interface depende dos parâmetros investigados. / [en] The displacement of a fluid caused by another one, inside annular
spaces, is commonly found in the oil industry and most of these
rearrangements involve non-Newtonian materials. The annular space often
shows irregularities caused by erosion, in which considerable amounts
of drilling fluid can be left behind during the displacement process,
compromising the cementing operation efficiency. Motivated by that
industrial process, fluid-fluid displacement tests at constant flow rate were
performed in annular spaces in which their exterior walls displayed -
in a determined axial position - an abrupt expansion followed by an
abrupt contraction. The purpose of the tests were to determine the
displacement efficiency as a function of flow rate, rheological properties
and geometric cavity. The results revealed a strong influence of these
parameters on the displacement efficiency. At the same time, a numerical
research was developed. Numerical simulations of the Navier-Stokes
equations in axisymmetric geometry for incompressible fluids were coupled
to the Level-Set method to capture the interface. Fluids with constant
viscosity and the generalized Newtonian model with viscosity function of
Carreau-Yasuda were used. That allowed to simulate displacements between
two Newtonian fluids and a Newtonian and a non-Newtonian fluid. This was
used both as a displacer and as a displaced fluid. Simulations were performed for several diameters and viscosities ratios, relaxatation time, capilar and Reynolds numbers. We identified when the approximation of the annular space by two parallel plates can be applied and calculated how the shape
of the interface depends on the investigated parameters.
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Microfluidic cells as a model 2D granular materialFantinel, Paolo 25 January 2017 (has links)
No description available.
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