This work investigates the performance of CO₂ soluble surfactants used for CO₂ foam flooding in fractured carbonate reservoirs. Oil recovery associated with the reduction of CO₂ mobility in fractures is assessed by monitoring oil saturation and pressure drops during injection of CO₂ with aqueous surfactant solution in artificially fractured carbonate cores. Distinct novel CO₂ soluble surfactants are evaluated as well as a conventional surfactant. Water flooding and pure CO₂ injection are conducted as baseline. Characterization of fluids and rock are also reported which include Amott test, oil phase behavior and slim tube test. Transport and thermodynamic properties of surfactant and supercritical CO₂ are used to evaluate the process on a core scale using a commercial reservoir simulator. / text

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.

Sur l’île de Majorque (Espagne), l’exploitation en continue de la nappe aquifère a favoriséla formation d’un biseau salé et l’épuisement de la ressource en eau potable. En 2002, un projet nommé ALIANCE, financé par l’Union européenne, a été lancé pour permettre une meilleure caractérisation des réservoirs. L’objectif est de concevoir un plan de gestion durable des ressources en eau dans les zones côtières aquifères sujets aux problèmes d’intrusion d’eau salée. Dans cet optique, un site expérimental près de la ville de Campos (Majorque) a été créé, avec la mise en place de plusieurs puits au sein d’un milieu karstique carbonaté. Des études pétrophysiques sur des échantillons ont été réalisées ainsi que différentes prospections géophysiques dans la zone saturée (tomographie puits à puits). Ce type d’études est utile pour déterminer certaines propriétés réservoirs telles que la porosité, mais sont limitées à la zone saturée au voisinage des puits. Ainsi, une étude sismique 3D haute résolution a été réalisée pour localiser les principaux réflecteurs, leurs répartitions sur la zone et imager les hétérogénéités du réservoir dans la zone non saturée. L’acquisition et le traitement de données sismiques lors de prospection de subsurface est une tâche difficile en raison de plusieurs facteurs, notamment logistique et technique. Cependant, cette acquisition 3D haute résolution a été optimisée pour imager une structure peu profonde, à savoir une centaine de mètres. Différentes stratégies de traitement de données ont été appliquées pour éliminer de manière efficace le bruit sur les données, et une technique de calcul de correction statique, basée sur l’inversion des temps de premières arrivées, a été mise au point. Différents attributs sismiques ont été extraits et utilisés pour la caratérisation du réservoir. La propagation des ondes sismiques est limitée par la nature des roches carbonatées et la création d’ondes de Rayleigh. Un obstacle majeur rencontré lors du traitement des données sismiques a été la présence d’ondes de Rayleigh de fortes amplitudes, d’une part due à l’utilisation d’une source en surface et d’autre part en raison des hétérogénéités de petite tailles. Un "mute" de ces ondes de surface a été réalisé avant d’imager la structure profonde. De multiples problèmes d’interférences sont également dus aux nombreuses hétérogénéités, à l’atténuation rapide du contenu hautes-fréquences des signaux et au contraste d’impédance avec les couches sous-jacentes. L’interprétation finale nous amène à observer que le réflecteur principal est très irrégulier sur une zone d’étude de petite taille à l’échelle d’un réservoir. L’analyse de différents attributs sismiques révèle clairement des structures et hétérogénéités typiques des systèmes karstiques. / Continuous water extraction and intrusion of salt water in the coastal aquifer of the islandof Mallorca (Spain) is depleting the fresh water aquifers. In 2002 a project named ALIANCE,funded by European Union, was initiated for better reservoir characterization and to devisethe sustainable management plan of the water resources in coastal aquifers suffering from salt water intrusion. For this purpose an experimental site near the Campos town on the island of Mallorca (Spain) was developed. Several wells on the site were drilled and cored. Extensive studies are carried out to characterize the reservoir by studying the well cores. Different geophysical tomographic studies are also carried out for these drilled wells in the saturated zone. Laboratory study of cores, petrophysical studies and several tomographic studies were helpful to construct the reservoir porosity system and other reservoir properties. But these all studies are restricted to saturated zone and in the vicinity of the wells. High resolution 3D seismic survey is carried out on this site to locate the different characteristic reflectors, their spatial presence over the area and reservoir heterogeneity in the unsaturated zone. Seismic data acquisition and processing for the shallow surveys is a difficult task due to number of factors including logistic and technical. Nonetheless high resolution 3D seismic survey is acquired with optimized parameters to image the required zone. Different data processing strategies are applied to get a noise free high resolution image. A technique for static correction calculation based on the delay time inversion is developed.Energy penetration in the subsurface was hampered due to carbonate rock nature and forced generation of Rayleigh waves. The processing of the seismic data was difficult due to overwhelming high amplitude Rayleigh waves that are generated partly due to use of the surface source and partly due to the small scale heterogeneities. Rayleigh wave muting is performed to obtain the meaningful image. Due to heterogeneities, attenuation of high frequency content of the signals and impedance contrast of the underlying layers result in interference. Different seismic attributes are extracted and used for reservoir characterization. From the interpretation of data it is evident that even for this small area the shape of the main reflector varies considerably in the area. Seismic attributes reveal karsts and other structural heterogeneities in the area.