Flow Visualization Studies of Foamy Oil Recreation Process for Extra Heavy Oil Recovery Using Glass Micromodel

Abstract

AbstractCold extra-heavy oil production in the Orinoco Heavy Oil Belt in Venezuela presents foamy oil behavior, with a primary recovery factor less than 12%. Studies on post-cold production process in extra-heavy oil reservoirs draw more and more attention in recent years. In previous studies, a novel non-thermal process, named Foamy Oil Recreation Process (FORP), was proposed. The process includes cyclic injection of compound fluid slugs, which is comprised of light hydrocarbon solvent as well as gas and surfactants (foaming agent and foam stabilizer), to promote the regeneration of foamy oil behavior, in a huff-n-puff manner. This paper was an extending experimental investigation of the pore scale behavior of the process. A series of flow visualization experiments were carried out to understand the foamy oil generation mechanism in the process using an etched glass micro-model, and to examine the effect of injection sequence, injection timing, ratio of gas to liquid (surfactant solution), and surfactant concentration on the regeneration of flow behavior of dispersed gas bubble in oil phase. A typical Heavy-Oil-Belt oil sample was used in the experiments. The experiment results show that the shearing action in pore medium plays an important role in the recreation of the foamy oil flow phenomenon. The division mechanism of gas bubbles includes elongation, pore throat cut-off etc. Compared to injection of gas and surfactant in sequence, co-injection of gas and surfactant can restrain the gas channeling to a higher scale. The bubble becomes unstable when the pressure is too low, and it is recommended to covert to FORP process from primary depletion when the formation pressure drops below the bubble point pressure while above the pseudo bubble point pressure. When the volume ratio of gas to liquid equals to 1, it is observed that highly dispersed and stable gas bubbles emerge in the micro-model. However, when the ratio of gas to liquid is too large, the film stability reduces and the bubble coalescence occurs more easily. With increase in surfactant concentration, the bubbles tend to be of small size and long duration, and the process will present even more obvious foamy oil flow behavior, and it is recommended that the surfactant concentration should be no less than 1.5wt%. This study presented suggestions on injection strategy for the novel FORP process, which could be used as guidance for further pilot-scale test design.KeywordsExtra-heavy oilFoamy oil behavior regenerationSurfactantCSSEOR