Paola Albonico

Nanoemulsion Flooding - The Journey to Field Begins

The continuous and growing request of energy worldwide, together with the depletion of the oil and gas resources, lead to an increasing interest to develop and apply EOR techniques in order to improve the production of already exploited reservoirs. In this scenario, current chemical EOR technologies are not yet widely applied, mainly for the high costs associated and high volumes required. “New” technologies and renovated chemical approaches must be implemented in order to make the chemical EOR processes extensively used. Among them, Nanotechnology seems to have an extraordinary potential to change production processes. Taking into account encouraging results recently achieved at laboratory scale using Nanoemulsions and aspiring to the field, the aim of this study was dual: on one hand render nanoemulsions cost effective and attractive for field applications, on the other hand, have a deeper understanding and knowledge of nanoemulsions mechanism of action and effect of on porous media. The two goals have been pursued with an intense formulative work based on a particular “low energy” proprietary method and using both bulk fluid characterizations and core floodings. Particular attention has been reserved to effluents observation and characterization in order to reveal criticalities associated to the application of this technology. A possible key role of the coexistence, in nanoemulsions, of small droplets size, surfactants mixture and solvent has been highlighted. In fact, these actors can favorably impact, in a synergic way, some critical parameters associated to oil recovery such as oil/water interfacial tension, wettability and oil viscosity. Surfactant adsorption/retention as well as rock/nanoemulsion interactions have been also evaluated. The future applicability of nanoemulsion strongly depends on its costs that can be reduced decreasing the amount of surfactants and solvent present in the formulation. This surely has an impact on nanoemulsion intrinsic structure (i.e. average droplet size, surface area) but not necessarily on the efficiency of mobilization of residual oil in porous media. Furthermore, alternative injection approaches can induce additional savings. The next phase foresees studies on injection strategies, the design of an up-scaled nanoemulsion production and nanoemulsion tuning on the basis of specific field parameters in order to render the technology suitable for a SWCTT.

Enhancing Oil Recovery with Nanoemulsion Flooding

Oil-in-water nanoemulsions are a particular class of emulsions where nanometric solvent droplets are dispersed in water using proper surfactant mixtures. Nanoemulsions can be formed with different techniques including high energy or low energy methods and, if properly formulated, can show very high kinetic stability as a direct consequence of monodispersity that minimize Ostwald Ripening effect and of the small droplet size that eliminates separation processes based on density difference. Their unique characteristics and physicochemical properties suggested their use as a “smart” displacing fluid for enhanced oil recovery (EOR). Even though the mechanism of residual oil mobilization is still not well known, the coexistence, in nanoemulsions, of small droplets size, surfactants mixture and solvent could favourably impact on critical parameters such as oil/water interfacial tension, wettability, oil viscosity. All these considerations induce to compare nanoemulsion flooding technology with the most common chemical EOR methods. This study presents examples of nanoemulsions prepared using a low energy proprietary method and a commercial surfactants mixture specifically tailored; this particular method allows to obtain very stable and, in many cases, mono-dispersed nanoemulsions using brines with different compositions (in order to mimic real field conditions) and a wide range of solvents with different features. These emulsions have been characterized in terms of physicochemical properties and size distribution of the dispersed oil droplets in water phase. Together with the basic characterization, core-flooding experiments have been carried out in order to evaluate the effectiveness of the nanoemulsions as displacing fluid for enhanced oil recovery and to investigate the mechanisms of mobilization of the residual oil in comparison with the classical chemical EOR methods.

Polymer Flooding - Designing of a Pilot Test for Unusually High Salinity and Hardness Reservoir

Reservoir conformance problems render uneven the flow of the injected water making waterflooding inefficient due to poor mobility control. This paper describes a systematic approach taken for the designing of a polymer flooding pilot test for a reservoir with challenging characteristics such as unusually high salinity and hardness that complicate the selection of the candidate polymer. This work includes a description of the characterization of a pre-selected candidate polymer, its rheological evaluation, its adsorption performance onto porous media, and its mechanical stability. Together with rheological properties, emphasis is given to the evaluation of flow performance of the polymer onto porous media at reservoir conditions. The experimental results indicate that the selected polymer (acrylamide/ATBS/acrylic acid ter-polymer) shows proper performance especially in terms of tolerance to reservoir salinity, hardness and high temperature. Numerical simulation studies demonstrate that polymer flooding at the selected zone could render a favourable incremental oil recovery (16%) over waterflooding.