Le polymer flooding est une des techniques de récupération assistée des hydrocarbures (RAH) ; elle consiste à injecter une solution de polymères de forte masse moléculaire afin de déplacer plus efficacement le pétrole emprisonné dans la roche. Cependant, une limite importante de cette technique est la possible dégradation mécanique des polymères au cours de l'injection et dans le réservoir, due à une scission des chaînes macromoléculaires induite par l’écoulement. Ce travail de thèse a pour objectif de mieux comprendre les mécanismes et scénarios de scission, mais aussi leur impact sur le procédé de polymer flooding. Nous nous sommes intéressés au seuil de dégradation mécanique de solutions de poly(oxyde d’éthylène) et de de polyacrylamide partiellement hydrolysé, pour différents régimes de concentration (solutions diluées et semi-diluées) en régime laminaire et inertiel, et pour des solvants de différentes qualités. L’étude de la dégradation mécanique des solutions et de leur impact sur les propriétés rhéologiques a été menée à l’aide de différents dispositifs de dégradation et de différents rhéomètres, dont un dispositif microfluidique en élongation ; ces techniques de mesure ont été combinées à des mesures de distribution de masses moléculaires par chromatographie d’exclusion stérique couplée à la diffusion de lumière. L’étude montre en premier lieu qu’une composante élongationnelle est indispensable pour dégrader les chaînes macromoléculaires en solution. Les résultats mettent aussi clairement en évidence que les mécanismes de dégradation sont très différents en régime dilué et semi-dilué. En régime dilué, la dégradation mécanique des solutions de polymères est indépendante du régime d’écoulement et affecte préférentiellement les macromolécules de fortes masses, avec une scission en milieu de chaîne. En revanche, en régime semi-dilué, la dégradation mécanique dépend du régime de l’écoulement : en écoulement laminaire, la dégradation est gouvernée par le réseau d’enchevêtrements et la scission des chaînes est aléatoire, tandis qu’en régime inertiel, les chaînes se dégradent comme en régime dilué, avec le même scénario de scission en milieu de chaîne. Par ailleurs, les résultats montrent que les propriétés rhéologiques en élongation peuvent être très fortement impactées par la dégradation mécanique. Enfin, les résultats de l’étude préliminaire des propriétés d’injectivité dans un milieu poreux d’une solution de polymère semi-diluée faiblement dégradée montrent que la dégradation mécanique améliore l’injectivité du polymère aux abords du puits. / Polymer flooding is a technique used in enhanced oil recovery; it consists in injecting high molecular weight polymer solutions in order improve oil sweep efficiency in the reservoir. However, polymer flooding is challenged by possible mechanical degradation of polymer solutions during injection and in the reservoir, due to the flow induced scission of macromolecules. This work aims at better understanding the scission mechanisms and scenarios, but also their impact on polymer flooding. We investigated the onset of mechanical degradation of poly(ethylene oxide) and partially hydrolysed polyacrylamide solutions, for different concentration regimes (dilute and semi-dilute regimes), under laminar or inertial conditions, but also under good or bad solvent conditions. The study of mechanical degradation of polymer solutions and their impact on the rheological properties was performed using different degradation devices and different rheometers, including a microfluidic extensional device; these investigation techniques were combined with measurements of the molecular weight distributions using size exclusion chromatography coupled with light scattering experiments. The study first shows that an extensional component is needed to get a mechanical degradation of polymer chains. The results also clearly show that the degradation mechanisms are very different in dilute and semi-dilute regime. In dilute regime, the mechanical degradation of polymer solutions does not dependent on flow regime and mainly affects the macromolecules with high molecular weights, with a mid-chain scission scenario. On the other hand, in semi-dilute regime, mechanical degradation depends on flow regime: in laminar flows, degradation is governed by the entanglement network and chain scission is random, whereas in inertial flows, chain degradation is similar to that observed in dilute regime, with the same mid-chain scission scenario. Besides, the results show that the extensional rheological properties can be very strongly affected by mechanical degradation. At last, the results of a preliminary study of the injectivity of a slightly degraded semi-dilute polymer solution in porous media show that mechanical degradation improves polymer injectivity near the wellbore.

A successful Chemical Enhanced Oil Recovery (CEOR) program starts with a proper process selection for a given field, followed by a formulation of the batch components and a representative simulation step. Also, lab studies, field data, pilot testing, and economic analyses are required before project implementation. This work discusses the state of the art of the Surfactant-Polymer flood (SP) EOR technique, specifically for carbonate reservoirs, and states a methodology mixing laboratory, literature and reservoir simulation, to assess its applicability under economic and geological uncertainties. First, it is explained concepts related to the research, such as polymer, surfactant, microemulsion, functionalities of each chemical injected, advantages, and disadvantages. Second, a state of the art is developed about recent SP advances. Third, it is described the laboratory method being used to evaluate some properties of the chemicals injected for the Polymer flooding (PF) and SP flooding. Later, the simulation study step being conducted is explained, which will define the volume recovered and Net Present Value (NVP) obtained for the PF, SP injections and water flooding, in different economic and geological scenarios for two models resembling carbonate Brazilian reservoirs. Finally, it is discussed the results obtained, future researches that could be performed, and the respective bibliography. As part of this research, it was verified the Xanthan gum shows adequate results at different concentrations; that a surfactant specifically selected for a carbonate rock with low Interfacial tension and low adsorption is required; also that for the Lula based model although the polymer flooding and Surfactant-Polymer simulation brought some benefits, when compared with the waterflooding, on different economic scenarios and geological models, the high cost associated to the chemical handling facilities and volume spent do not make favorable its application in any scenario. On the contrary for the Cerena I field model, it was found the SP and Polymer flooding on all cases brought better results when compared with the water injection. Concluding that the performance and success of a CEOR program require finding the correct slug characteristics for the unique conditions of each reservoir. In this research the reservoir with higher production rates made possible the use of Chemical EOR presenting better results than a water injection however in the smaller model they were not economically viable due to the additional associated prices. / Um programa bem-sucedido de recuperação melhorada de petróleo por método químico (CEOR) começa com uma seleção precisa do processo para um determinado campo, seguido pela formulação dos componentes e uma etapa de formulação representativa. Adicionalmente, testes laboratoriais, dados de campos, testes pilotos e análises econômicas são necessárias antes da implementação de um projeto. Este trabalho discute o estado da arte da técnica de recuperação melhorada de petróleo (EOR) pela injeção de surfactante-polímero (SP), especificamente para reservatórios carbonáticos e, utilizada uma metodologia baseada em dados de laboratório, literatura e de simulação de reservatório para avaliar sua aplicabilidade sob incertezas econômicas e geológicas. Primeiramente, são explicados conceitos necessários a este trabalho relacionados com polímero, surfactante, microemulsão, funcionalidades de cada produto químico injetado, vantagens e desvantagens. Em segundo lugar, um estado da arte é desenvolvido sobre os avanços recentes do SP. Após, descreve-se os métodos laboratoriais utilizados para avaliar algumas propriedades dos produtos químicos usados nas injeções de Polímeros (PF) e SP. Posteriormente, é explicada a etapa do estudo de simulação, que definirá o volume recuperado e o valor presente líquido (NVP), obtidos para injeções PF, SP e água, em diferentes cenários econômicos e geológicos, para dois modelos semelhantes a reservatórios carbonáticos brasileiros. Por fim, são discutidos os resultados obtidos, sugestões de trabalhos futuros e apresentação da bibliografia. Como parte desta pesquisa, verificou-se que a goma xantana apresenta resultados consistentes em diferentes concentrações e que é necessário um surfactante especificamente selecionado para uma rocha carbonática, possuindo baixa tensão interfacial e baixa adsorção. Para o modelo baseado em Lula, embora a simulação de injeção de polímero e surfactante-polímero tenham trazido alguns benefícios, quando comparados com a injeção de água, em diferentes cenários econômicos e modelos geológicos, o alto custo associado às instalações de manipulação química e volume gasto não favorece sua aplicação em qualquer cenário. Por outro lado, no modelo de campo Cerena I, verificou-se que as injeções de SP e de polímero, em todos os casos, trouxeram melhores resultados quando comparadas com a injeção de água. Concluindo, o desempenho e o sucesso de um programa de CEOR exige encontrar as corretas características de slugs para condições únicas de cada reservatório. Neste trabalho, o reservatório com maiores taxas de produção infere que o método químico de EOR apresente melhores resultados quando comparado com a injeção de água.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-01-13T13:25:29Z No. of bitstreams: 1 pavelzenonsejaspaz.pdf: 1021401 bytes, checksum: 6c80da770310ced9141a330e3a4d4f9b (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-01-25T17:32:38Z (GMT) No. of bitstreams: 1 pavelzenonsejaspaz.pdf: 1021401 bytes, checksum: 6c80da770310ced9141a330e3a4d4f9b (MD5) / Made available in DSpace on 2016-01-25T17:32:38Z (GMT). No. of bitstreams: 1 pavelzenonsejaspaz.pdf: 1021401 bytes, checksum: 6c80da770310ced9141a330e3a4d4f9b (MD5) Previous issue date: 2015-08-28 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho apresentamos um estudo analítico sobre a recuperação de óleo pesado utilizando injeção de água, que é aquecida por meio de ondas eletromagnéticas de alta freqüência. Recentemente, foi feito um experimento (descrito em [12]), onde a água foi injetada num meio poroso, aquecida por meio de ondas eletromagnéticas. Os resultados do experimento mostram que o aquecimento mediante ondas EM melhora o deslocamento do óleo pela água. Desta maneira, apresenta-se a injeção de água com aquecimento por ondas EM como um método viável na recuperação de óleo. Consideraremos um modelo matemático simples descrevendo o experimento mencionado acima, que consiste de duas leis de balanço, uma para a energia e outra para a massa da água. O objetivo do trabalho é usar o Princípio de Duhamel e a Teoria das Leis de Conservação para encontrar soluções semi-analíticas deste modelo simplificado. Segundo [8], utilizamos o Princípio para achar a solução da equação de balanço de energia do tipo Convecção-Reação-Difusão para o problema de transporte de calor num meio poroso na presença de uma fonte de ondas eletromagnéticas. A equação de balanço para a massa da água é uma equação diferencial parcial não linear de primeira ordem do tipo Buckley-Leverett (Veja [4] e [7]). Ela será resolvida usando a Teoria das Leis de Conservação. Segundo [15], a solução deste problema contém ondas de rarefação e choque. / In this work, we present the results obtained by analytical study of heavy oil recovery by water flooding and electromagnetic (EM) heating of high frequency. Recently, an experiment was made, where water was injected into a porous medium, warmed by means of electromagnetic waves. The experiment results show that EM heating improves the displacement of oil by water. Thus, the water flooding combined with EM heating is a viable method for oil recovery. We consider a simple mathematical model describing this experiment consisting of two balance laws for energy and water mass. The goal is to use Duhamel’s Principle and the Theory of Conservation Laws to find semi-analytical solutions of this simplified model. We use the principle solve the energy balance equation of convection-reaction-diffusion type for heat transport problem in a porous medium in the presence of a source of electromagnetic waves. The balance equation for the mass of water is a nonlinear partial differential equation of first order of Buckley-Leverett type. It is solved using the Theory of Conservation Laws.

<p>Crude oil is a mixture of hydrocarbons so complex that it is predicted to comprise as many compounds as there are genes in the human genome. Developing methods to not only recover crude oil from the ground but also to convert crude oil into desirable products is challenging due to its complex nature. Thus, the petroleum industry relies heavily on analytical techniques to characterize the oil in reservoirs prior to enhanced oil recovery efforts and to evaluate the chemical compositions of their crude oil based products. Mass spectrometry (MS) is the only analytical technique that has the potential to provide elemental composition as well as structural information for the individual compounds that comprise petroleum samples. The continuous development of ionization techniques and mass analyzers, and other instrumentation advances, have primed mass spectrometry as the go-to analytical technique for providing solutions to problems faced by the petroleum industry. The research discussed in this dissertation can be divided into three parts: developing novel mass spectrometry-based methods to characterize mixtures of saturated hydrocarbons in petroleum products (Chapters 3 and 5), exploring the cause of fragmentation of saturated hydrocarbons upon atmospheric pressure chemical ionization to improve the analysis of samples containing these compounds (Chapter 4), and developing a better understanding of the chemical composition of crude oil that tightly binds to reservoir surfaces to improve chemically enhanced oil recovery (Chapter 6). </p>

No description available.

[pt] A inundação com água de baixa salinidade é uma estratégia de recuperação avançada de petróleo (EOR) em reservatórios carbonatados, onde a concentração e composição da salmoura são cruciais para a remoção do óleo. Este estudo investigou os aspectos químicos e físicos da inundação com água de baixa salinidade e seu impacto na recuperação de petróleo, focando na interação e modificações na interface óleo-calcita. Medidas de FTIR foram utilizadas para caracterizar a adsorção e quantificar a remoção de óleo mineral Nujol em monocristais de calcita clivados no plano (104), antes e após condicionamentos nas salmouras em diferentes condições. Os resultados mostraram que o Nujol forma um filme contínuo na superfície da calcita, impedindo sua dissolução nas condições de condicionamento nas salmouras de menor teor de sal. A quantidade de óleo removido variou conforme a salinidade da salmoura. Nas condições experimentais investigadas, a superfície de calcita recém clivada é mais eficientemente convertida de oleofílica para hidrofílica quando condicionada em condição de salinidade intermediaria (LS75). A remoção de óleo foi quantificada por meio de análise FTIR semiquantitativa, variando de aproximadamente 20 por cento de óleo removido para água de formação (FW) até cerca de 81 por cento após condicionamento em LS75. A análise espectroscópica indicou uma competição entre a incorporação de espécies iônicas da salmoura na interface e a dissolução da calcita, afetando diretamente na cristalinidade da superfície. O condicionamento com água deionizada (DW) não resultou na remoção ideal de óleo devido à maior dissolução e readsorção de moléculas de óleo. O estudo também constatou que o magnésio exerceu maior influência na remoção de óleo da superfície em comparação com o cálcio. As superfícies previamente hidratadas com FW e DW apresentaram alterações significativas. A hidratação com FW não necessariamente causa dissolução, mas promove a adsorção de grupos OH, criando pontos de ancoragem para o óleo. Em contraste, a hidratação com DW resultou na perda de cristalinidade, gerando defeitos na superfície. Em ambos os casos, foram observadas mudanças nas bandas de vibração características do nujol, sugerindo diferentes interações do óleo com a superfície. Comparando a quantidade de óleo adsorvida nas três condições estudadas, a calcita hidratada com FW apresentou a maior quantidade de óleo adsorvido, associado à adsorção de íons na superfície. / [en] Low salinity water flooding is an advanced oil recovery (EOR) strategy in carbonate reservoirs, where the concentration and composition of the brine are crucial for oil removal. This study investigated the chemical and physical aspects of low salinity water flooding and its impact on oil recovery, focusing on the interaction and modifications at the oil-calcite interface. FTIR measurements were used to characterize the adsorption and quantify the removal of mineral oil Nujol on calcite single crystals cleaved along the (104) plane, before and after conditioning in brines under different conditions. The results showed that Nujol forms a continuous film on the calcite surface, preventing its dissolution under aging conditions in lower salinity brines. The amount of oil removed varied according to the salinity of the brine. Under the experimental conditions investigated, the freshly cleaved calcite surface is more efficiently converted from oleophilic to hydrophilic when conditioned in intermediate salinity condition (LS75). The oil removal was quantified using semiquantitative FTIR analysis, ranging from approximately 20 percent for formation water (FW) to about 81 percent after conditioning in LS75. Spectroscopic analysis indicated a competition between the incorporation of ionic species from the brine at the interface and the dissolution of calcite, directly affecting the surface crystallinity. Conditioning with deionized water (DW) did not result in optimal oil removal due to increased dissolution and re-adsorption of oil molecules. The study also found that magnesium had a greater influence on oil removal from the surface compared to calcium. The surfaces previously hydrated with FW and DW showed significant alterations. Hydration with FW does not necessarily cause dissolution but promotes the adsorption of OH groups, creating anchoring points for the oil. In contrast, hydration with DW resulted in a loss of crystallinity, generating defects on the surface. In both cases, changes in the characteristic vibration bands of nujol were observed, suggesting different interactions of the oil with the surface. Comparing the amount of oil adsorbed under the three conditions studied, the calcite hydrated with FW showed the highest amount of adsorbed oil, associated with ion adsorption on the surface.

Reservoir simulation is a powerful tool to model fluid flow within oil and gas reservoirs and predict their behaviour. This dissertation is devoted primarily to model some thermal enhanced oil recovery (TEOR) methods. Two software were used for this purpose and namely; Comsol Multiphysics® and CMG® (Computer Modelling Group). The dissertation can be classified into three parts and all of them are standalone that discuss different topics within TEOR. The work starts with reviewing enhanced oil recovery (EOR) methods with concentration on thermal methods (TEOR) for heavy oil and bitumen. Basics of mathematical modelling of single, two-phase, and three-phase flow in porous media that is the base of all commercial and scientific reservoir simulation software are reviewed. Formulations of the set of representative PDEs are reviewed and other formulations are suggested and applied directly in subsequent sections in Comsol Multiphysics®. Part-1: The application of finite element method (FEM) in reservoir simulation has been discussed and evaluated using Comsol Multiphysics package which is based on Galerkin approach. In the demonstrated problems, the mathematical model is solved using mathematics module in Comsol Multiphysics. Energy equation in 1D, Buckley-Leverett benchmark, two-phase flow model on ¼ inverted 5-spot scheme in 3D, and SAGD process PDE model are all solved and discussed. FEM using Comsol Multiphysics looks promising at moderate mobility ratios. Part-2: A comparison of water flooding with steam injection in heavy oil reservoirs as secondary stage is demonstrated and discussed. The whole modelling was achieved by CMG-STARS. A comparison of five different scenarios is shown. SPE4 comparative project data were used for this purpose. The results showed that steam can achieve more recovery in a short period of time with an ultimate recovery factor higher than cold recovery followed by steam flooding process. Part-3: A series of flooding and in-situ combustion experimental work that has been achieved in Kazan Federal University in cooperation with Institute of Drilling Engineering and Fluid Mining (IBF) is elaborated briefly and discussed. Four experiments with different core samples (consolidated and unconsolidated) were run between 05-2020 and 05-2021. The samples were taken from a Russian extra-heavy oilfield with initial viscosity around 600,000 cP. The results were evaluated and a numerical model was built using CMG-STARS. The numerical results were correlating the experimental results. Relative permeability data were history matched for flooding processes and this data was used for in-situ combustion model. Modelling of the reactions in in-situ combustion was a challenge to match the experimental results. The final results showed that steam injection was not the best recovery method for this oilfield and in-situ combustion was the best available technique with the highest recovery factor.

The topic of this thesis is carbon dioxide (CO2) capture and storage (CCS), which is a technology that is currently being promoted by industries, scientists and governments, among others, in order to mitigate climate change despite a continued use of fossil fuels. Because of the complex nature of CCS and the risks it entails, it is controversial. The aim of this thesis is to analyse how the technology may be further developed in a responsible manner. In the first part of the thesis different methods for capturing CO2 from industrial processes as well as power plants are analysed. The aim is to identify early opportunities for CO2 capture, which is considered important because of the urgency of the climate change problem. Three potential early opportunities are studied: i) capturing CO2 from calcining processes such as cement industries by using the oxyfuel process, ii) capturing CO2 from pressurised flue gas, and iii) capturing CO2 from hybrid combined cycles. Each opportunity has properties that may make them competitive in comparison to the more common alternatives if CCS is realised. However, there are also drawbacks. For example, while capturing CO2 from pressurised flue gas enables the use of more compact capture plant designs as well as less expensive and less toxic absorbents, the concept is neither suitable for retrofitting nor has it been promoted by the large and influential corporations. The second part of the thesis has a broader scope than the first and is multidisciplinary in its nature with inspiration from the research field of Science and Technology Studies (STS). The approach is to critically analyse stakeholder percep-tions regarding CCS, with a specific focus on the CCS experts. The thesis sheds new light on the complexity and scientific uncertainty of CCS as well as on the optimism among many of its proponents. Because of the uncertain development when it comes to climate change, fossil fuel use and greenhouse gas emissions, the conclusion is that CCS has to be further developed and demonstrated. A responsible strategy for a future development of CCS would benefit from: i) a search for win-win strategies, ii) increasing use of appropriate analytical tools such as life-cycle analysis, iii) a consideration of fossil fuel scarcity and increasing price volatility, iv) funding of unbiased research and v) increasing simultaneous investments in long-term solutions such as renewable energy alternatives and efficiency improvements. / QC 20100727

Canada has the second largest proven oil reserves next to Saudi Arabia which is mostly located in Alberta and Saskatchewan but is unconventional heavy oil and bitumen. The tar sands are found at the surface and are mined, yet 80% of the 173 billion barrels of heavy oil and bitumen exist in-situ according to the Canadian Association of Petroleum Producers (CAPP). Two factors inhibit the economic extraction and processing of Canadian heavy oil; its enormous viscosity ranging from 1000 to over 1 million mPa.s and the asphaltene content (high molecular weight molecules containing heavy metals and sulphur). Heavy oil and bitumen were only included in the reserves estimates through the efforts of Canadian enhanced oil recovery (EOR) research. Viscosity reduction is the one common element of in-situ methods of heavy oil recovery with the exception of cold production. Currently, steam assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) are being used commercially in the field where the oil’s viscosity is reduced by injecting steam. Thermal methods are energy intensive requiring vast volumes of water such that any improvement would be beneficial. Solvent extraction is one alternative requiring no water, the solvent is recoverable and reusable, and depending on the mode of operation the heavy oil is upgraded in-situ. Vapour Extraction (VAPEX) and enhanced solvent extraction (N-SolvTM) are two such methods. VAPEX and N-Solv reduce the bitumen’s viscosity via mass transfer and a combination of mass and heat transfer, respectively. A light hydrocarbon solvent (instead of steam) is injected into an upper horizontal well where the solvent mixes with the heavy oil, reduces its viscosity and allows the oil to drain under gravity to a bottom production well. The idea of using solvents for heavy oil extraction has been around since the 1970s and both VAPEX and N-Solv are patented processes. However, there is still much to be learned about how these processes physically work. Research to date has focused on varying system parameters (including model dimensions, permeability, heavy oil viscosity, solvent type and injection rate, etc.) to observe the effect on oil production from laboratory scale models. Based on an early mass balance model by Butler and Mokrys (1989) and an improvement by Das (1995), molecular diffusion alone cannot account for the produced oil rates observed from laboratory models. Until recently, very little progress had been made towards qualifying and quantifying the mass transfer mechanisms with the exception of the diffusivity of light hydrocarbons in heavy oil. Mass transfer can only be by diffusion and convection. Differentiating and quantifying the contribution of each is complex due to the nature and viscosity of the oil. The goal of this thesis is to investigate the mass transfer mechanisms during the solvent recovery of heavy oil. Quantifying the diffusion of light hydrocarbon solvents has been an active topic of research with limited success since the mid 1990’s. The experimental approach presented here focused on capturing the rate of solvent mass transfer into the bitumen by measuring the bitumen swelling and the butane uptake independently. Unlike early pressure decay methods, the pressure is held constant to not violate the assumed equilibrium solvent concentration at the interfacial boundary condition. The high solubility of solvent in heavy oil complicates the physical modeling because simplifying assumptions of a constant diffusion coefficient, constant density and a quiescent liquid should not be used. The model was developed from first principles to predict the bitumen swelling. The form of the concentration dependent diffusivity was assumed and the diffusivity coefficients initially guessed. The swelling (moving boundary) was fixed by defining a new dimensionless space coordinate and the set of partial differential equations solved using the method of lines. Using the non-linear regression (lsqnonlin) function in MATLAB®, optimising for the difference in predicted and experimentally found bitumen heights and independently validating the result using the solvent uptake, the diffusivity of butane in heavy oil (at 25oC) was found to be Dsb = 4.78 x 10-6ωs + 4.91 x 10-6 cm2/s where ωs is the solvent mass fraction. Diffusion alone has proven inadequate in predicting oil recovery rates from laboratory scale models. It is logical to assume that convective mass transfer plays a role at mixing the solvent and bitumen while draining via gravity through the reservoir porous matrix. Solvent extraction experiments were conducted in etched glass micromodels to observe the pore scale phenomena. The pore scale mechanisms were found to differ depending on how the solvent extraction was operated, with non-condensing (VAPEX) or condensing (N-SolvTM) solvent. Observations show increased convective mixing and an increased rate of interface advancement when the solvent condenses on the bitumen surface. Evidence of trapped butane vapour being mobilised with the draining live oil and a technique of observing solvent extraction using UV light confirm that the draining live oil is on average one pore deep. While the interface appears from a distance to be uniform, at the pore scale it is not. Live oil can drain from one to two pores via capillary displacement mechanisms in one section of the interface and via film flow only in another area (James and Chatzis 2004; James et al. 2008). This work also shows the detrimental impact of having a non-condensable gas present during solvent extraction (James and Chatzis 2008). In summary, this work emphasises the mass transfer and drainage displacement mechanisms of non-condensing (VAPEX) and condensing (N-Solv) solvent extraction methods of heavy oil recovery.

Canada has the second largest proven oil reserves next to Saudi Arabia which is mostly located in Alberta and Saskatchewan but is unconventional heavy oil and bitumen. The tar sands are found at the surface and are mined, yet 80% of the 173 billion barrels of heavy oil and bitumen exist in-situ according to the Canadian Association of Petroleum Producers (CAPP). Two factors inhibit the economic extraction and processing of Canadian heavy oil; its enormous viscosity ranging from 1000 to over 1 million mPa.s and the asphaltene content (high molecular weight molecules containing heavy metals and sulphur). Heavy oil and bitumen were only included in the reserves estimates through the efforts of Canadian enhanced oil recovery (EOR) research. Viscosity reduction is the one common element of in-situ methods of heavy oil recovery with the exception of cold production. Currently, steam assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) are being used commercially in the field where the oil’s viscosity is reduced by injecting steam. Thermal methods are energy intensive requiring vast volumes of water such that any improvement would be beneficial. Solvent extraction is one alternative requiring no water, the solvent is recoverable and reusable, and depending on the mode of operation the heavy oil is upgraded in-situ. Vapour Extraction (VAPEX) and enhanced solvent extraction (N-SolvTM) are two such methods. VAPEX and N-Solv reduce the bitumen’s viscosity via mass transfer and a combination of mass and heat transfer, respectively. A light hydrocarbon solvent (instead of steam) is injected into an upper horizontal well where the solvent mixes with the heavy oil, reduces its viscosity and allows the oil to drain under gravity to a bottom production well. The idea of using solvents for heavy oil extraction has been around since the 1970s and both VAPEX and N-Solv are patented processes. However, there is still much to be learned about how these processes physically work. Research to date has focused on varying system parameters (including model dimensions, permeability, heavy oil viscosity, solvent type and injection rate, etc.) to observe the effect on oil production from laboratory scale models. Based on an early mass balance model by Butler and Mokrys (1989) and an improvement by Das (1995), molecular diffusion alone cannot account for the produced oil rates observed from laboratory models. Until recently, very little progress had been made towards qualifying and quantifying the mass transfer mechanisms with the exception of the diffusivity of light hydrocarbons in heavy oil. Mass transfer can only be by diffusion and convection. Differentiating and quantifying the contribution of each is complex due to the nature and viscosity of the oil. The goal of this thesis is to investigate the mass transfer mechanisms during the solvent recovery of heavy oil. Quantifying the diffusion of light hydrocarbon solvents has been an active topic of research with limited success since the mid 1990’s. The experimental approach presented here focused on capturing the rate of solvent mass transfer into the bitumen by measuring the bitumen swelling and the butane uptake independently. Unlike early pressure decay methods, the pressure is held constant to not violate the assumed equilibrium solvent concentration at the interfacial boundary condition. The high solubility of solvent in heavy oil complicates the physical modeling because simplifying assumptions of a constant diffusion coefficient, constant density and a quiescent liquid should not be used. The model was developed from first principles to predict the bitumen swelling. The form of the concentration dependent diffusivity was assumed and the diffusivity coefficients initially guessed. The swelling (moving boundary) was fixed by defining a new dimensionless space coordinate and the set of partial differential equations solved using the method of lines. Using the non-linear regression (lsqnonlin) function in MATLAB®, optimising for the difference in predicted and experimentally found bitumen heights and independently validating the result using the solvent uptake, the diffusivity of butane in heavy oil (at 25oC) was found to be Dsb = 4.78 x 10-6ωs + 4.91 x 10-6 cm2/s where ωs is the solvent mass fraction. Diffusion alone has proven inadequate in predicting oil recovery rates from laboratory scale models. It is logical to assume that convective mass transfer plays a role at mixing the solvent and bitumen while draining via gravity through the reservoir porous matrix. Solvent extraction experiments were conducted in etched glass micromodels to observe the pore scale phenomena. The pore scale mechanisms were found to differ depending on how the solvent extraction was operated, with non-condensing (VAPEX) or condensing (N-SolvTM) solvent. Observations show increased convective mixing and an increased rate of interface advancement when the solvent condenses on the bitumen surface. Evidence of trapped butane vapour being mobilised with the draining live oil and a technique of observing solvent extraction using UV light confirm that the draining live oil is on average one pore deep. While the interface appears from a distance to be uniform, at the pore scale it is not. Live oil can drain from one to two pores via capillary displacement mechanisms in one section of the interface and via film flow only in another area (James and Chatzis 2004; James et al. 2008). This work also shows the detrimental impact of having a non-condensable gas present during solvent extraction (James and Chatzis 2008). In summary, this work emphasises the mass transfer and drainage displacement mechanisms of non-condensing (VAPEX) and condensing (N-Solv) solvent extraction methods of heavy oil recovery.