Foam, a dispersion of gas in liquid, has been investigated as a tool for gas-mobility and conformance control in porous media for a variety of applications since the late 1950s. These applications include enhanced oil recovery, matrix-acidization treatments, gasleakage prevention, as well as contaminated-aquifer remediation. To understand the complex physics of foam in porous media and to implement foam processes in a more-controllable way, various foam-modeling techniques were developed in the past 3 decades.This paper reviews modeling approaches obtained from different publications for describing foam flow through porous media. Specifically, we tabulate models on the basis of their respective characteristics, including implicit-texture as well as mechanistic population-balance foam models. In various population-balance models, how foam texture is obtained and how gas mobility is altered as a function of foam texture, among other variables, are presented and compared. It is generally understood that both the gas relative permeability and viscosity vary in the reduction of gas mobility through foam generation in porous media. However, because the two parameters appear together in the Darcy equation, different approaches were taken to alter the mobility in the various models: only reduction of gas relative permeability, increasing of effective gas viscosity, or a combination of both. The applicability and limitations of each approach are discussed. How various foam-generation mechanisms play a role in the foam-generation function in mechanistic models is also discussed in this review, which is indispensable to reconcile the findings from different publications. In addition, other foam-modeling methods, such as the approaches that use fractional-flow theory and those that use percolation theory, are also reviewed in this work. Several challenges for foam modeling, including model selection and enhancement, fitting parameters to data, modeling oil effect on foam behavior, and scaling up of foam models, are also discussed at the end of this paper.

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Molecular diffusion of gases in heavy oils is one of the most important physical parameter governing cold production processes such as solution gas drive or Vapex. Indeed, the way bubbles are able to grow by diffusion will have a direct impact on gas mobilization and consequently on oil recovery. Furthermore, the importance of this parameter is emphasized by the very low gas availability characterizing extra heavy oils.Surprisingly, publications of experimental data concerning gas diffusivity in heavy oils are relatively rare. Furthermore, published values can vary by different orders of magnitude. This is probably due to the fact that this kind of measurement is quite tricky. Indeed gas leakages in high pressure cells could be in the same order of magnitude than gas diffusion in oil. To study very viscous oil (extra heavy oils), corresponding to very low diffusivity, it is thus necessary to carefully analyze the obtained results.The aim of this work is to characterize experimental fickian diffusivity of methane in heavy oils using two different concepts in order to be able to validate the experimental results. In this paper we present the two different methods (thermophysics and analytical) we have settled. Experimental results clearly indicate that diffusivity in extra heavy oils is lower than usually considered for 'conventional' oil.From various experimental results we also propose a first mathematical model to simulate the influence of temperature on gas diffusivity.

The Polymer Injection Project on Dalia field, one of the main fields of Block 17 in deep offshore Angola, is a world first for both surface and subsurface aspects. Thorough geosciences and architecture integrated studies led to decide to phase the project, with a polymer injectivity test on one single well, followed by a continuous injection of polymer on one of the four subsea lines delivering water to the field. The single well injectivity test on DAL-710 was completed first quarter of 2009, just two years after first oil. Very successful results led to launch a polymer injection pilot on the full injection line of the Camelia reservoir. The main objectives of the single line Camelia pilot were to confirm long term operability and injectivity of polymer in the specific conditions of this deep-offshore development, and measure the in situ viscosity (sampler well) of the injected polymer solution away from the injector, as key inputs to the evaluation of an extended project. From February 2010 to August 2012, a 900 ppm polymer solution was injected through the three wells of the line. In summer 2012, a sampler well was drilled 80 m far from one of the injector, located behind the polymer front thanks to 4D seismic monitoring. MDT and bottom hole samples were done and analyzed. The paper describes the main results of the pilot phase on injectivity, operability and polymer sampling. The pilot answered its objectives, but still a lower viscosity than expected was measured in the sampler well. Key deliverables were: • How to operate the whole process chain of viscosified water at topsides level • Better knowledge of polymer degradation from topside to deep into the reservoir • Data required to properly size an extended polymer project.

Rules of thumb that are used in the industry for polymer-flooding projects tend to limit the distance over which hydrolyzed polyacrylamide polymers can be transported in pipelines without undergoing significant degradation. However, in sensitive environments, such as offshore facilities where footprint minimization is required, centralization of the polymer-hydration process and long-distance transport may be desirable. More-reliable rules are required to design the pipe network and to estimate mechanical degradation of polymers during transport in turbulent conditions.In this work, we present evidence in the form of empirical largescale pipeline experiments and theoretical development refuting the claim that polymer pipeline transport is limited by mechanical degradation. Our work concludes that mechanical degradation occurs at a critical velocity, which increases as a function of pipe diameter. Provided the critical velocity is not reached in a given pipe, there is no limit to the distance over which polymer solution can be transported.In addition, the drag reduction of viscous polymer solutions was measured as a function of pipe length, pipe diameter, fluid velocity, and polymer concentration. An envelope was defined to fix the minimum and maximum drag reductions expected for a given velocity in larger pipes. For pipes with diameters varying between 14 and 22 in. at a velocity greater than 1 m/s, the drag-reduction percentage is anticipated to be between 55 and 80%. A morerefined model was developed to predict drag reduction with less uncertainty.In conclusion, classical design rules applied for water transport (fluid velocity < 3 m/s) can be applied to the design of a polymer network. Therefore, for tertiary polymer projects, the existing water-injection network should be compatible with the mechanical requirements of polymer transportation. For secondary polymer projects, changing the rules of design by taking into account the high level of drag reduction should bring some economy to the pipe design and installation.