In La Salina field, located in the Maracaibo Lake, Venezuela, which produces a medium gravity crude oil (25 API) from a Miocene reservoir at 3,000 feet, a series of EOR processes were proposed to be evaluated under field conditions. Results from laboratory tests indicated that Alkali-Surfactant-Polymer technology (ASP) might be a potential EOR process to improve the oil recovery factor. However, ASP processes involve the injection of a significant volume of chemicals, therefore, costs associated with this technology could exceed the economical limit permissible. For this reason, it is necessary to use simulation tools to predict reservoir production response when this technology is applied. Results from early ASP simulations have been reported elsewhere [1, 2].
The present study shows the results of modeling the injection of ASP in a pilot area of La Salina field, using two commercial simulators. The pilot area has been partially depleted by waterflooding, therefore the reservoir still contains mobile oil saturation. Based on laboratory history matches of radial core floods, several field predictions were carried out which show an incremental oil recovery factor between 6% and 16.7% compared to waterflooding, depending on the selected well arrangements and the volume of injected chemicals. The results of the two simulators were compared at both scales, and in spite of formulation differences between them, the answers were very similar. Additionally, sensitivities on certain critical variables that can influence the success of future tests were established. These include chemical formulation variables such as interfacial tension reduction and component adsorption levels, as well as field injection rates, treatment volume, and injection time. Also, different well arrangements were evaluated, including drilling and positioning of infill wells. The simulations have given confidence with regard to the applicability of ASP in the La Salina field, and preparations for a pilot test are underway.
The injection of solutions of alkali-surfactant-polymer (ASP) for the improved sweep efficiency and mobilization of residual oil has been amply reported around the world with a high percentage of success. This technology which combines the effects of reduced interfacial tension (alkali and surfactant) which reduces the capillary forces which have left oil trapped in the porous media during water injection, and the effect of mobility control (polymer) which increases the contact between displacing and displaced phases increasing the sweep efficiency, has been tried mostly in China and the United States [1,2].
In the Integrated Field Laboratory (IFL) La Salina, a series of increased recovery options have been proposed, in which the ASP technology was demonstrated to have the potential and conditions necessary to achieve an impact on the oil recovery. In this sense, a feasibility study was realized [4] based on a series of laboratory tests, which included the following experiments: fluid compatibilities, thermal stability and chemical spontaneous emulsification, interfacial tension between the oil and the ASP solution, chemical retention in the porous media, and and physical simulation using reservoir cores.
Nevertheless, it is necessary that the ASP application requires a significant volume of injected chemicals, the costs associated with the technology could increase beyond permitted economic limits.
