Evolution of Foamed Gel Confined in Pore Network Models

Abstract Conventional foams and foamed gels present a variety of relevant propertiesthat make them suitable for important uses in the oil and gas sector. Some ofthese applications include drilling operations, CO2-foam injection, steam-foam, foam assisted water alternate gas (WAG), and gas shut-offtechniques to control excessive gas production in oil wells. Foamed gels havealso demonstrated great potential as gas and liquid diverting fluids.Furthermore, foam systems can be injected into rock formations as an importantmeans for CO2 and green gases recycling. In foamed gel applications, an issue of particular interest is theunderstanding of the evolution of partially gelled foam bubbles confined inporous media. The significance of this evaluation is the fact that after foamedgel placement in porous media, the pore-level configuration of the gelledlamellarstructure determines the fluid diverting performance of mature foamedgel barriers. This paper reports the experimental results of a pore level visualization studyconducted to evaluate the evolution of foamed gel after placement in porousmedia as a function of aging time. In addition, the experiments assisted in theexamination of the effect of rock wettability, foamed gel texture, type of gasused for foamed gel formulation, and type of oil that saturates the porousmedia play on the evolution of confined foamed gel. Etched-glass micromodelsand Helle Shaw cells were used to visualize the growth of foamed gel bubbles asa function of time. Through image analysis changes on bubble sizes werequantified and statistically analyzed. Laboratory evidence indicates that right after immature foamed gel placement inetched-glass micromodels significant changes in bubble size occur. After thefirst 20 hours of foamed gel placement inside the pore network model, bubblegrowth levels off. The lamellar-structure in the micromodel reaches a stableconfiguration, which remains steady for an indefinite period if externalinstabilities are absent. Quite the opposite was observed when the same foamedgel was placed in a Helle Shaw cell. In this case, due to the absence ofgeometric restrictions, homogeneous bubble shapes and rapid bubble growth wereobserved. The experimental results demonstrated that porous media wettability, foamed geltexture, the type of gas used for foamed gel production, and the type of oilthat saturates the pore models, significantly influence the evolution of foamedgel confined in porous media. Introduction Studies of foams in pore network models allow the visualization of foamperformance during propagation and after placement within the porous media. Themain advantage of this pore-level visualization studies is the possibility ofrecognizing important mechanisms, which are useful to elucidate foamperformance under different experimental conditions. In the case of immature foamed gels, an issue of particular interest is theunderstanding of the mechanisms of bubble growth after placement in porousmedia. As Miller et al. (1) explained, the performance of maturefoamed gel barriers is directly related to the pore level configuration of thefoamed gel, specifically, the number and location of gelled lenses that plugflow paths. Consequently, it is crucial to characterize the long-term evolutionof gelled foam bubbles trapped in porous media (2). s trapped in porous media(2).