Research on the Properties of Natural Gas Foamed Gel as a Profile Control and an Oil Displacement Agent in Strong Heterogeneous Reservoirs

Abstract

To alleviate the uneven production of extreme heterogeneous reservoirs, we developed a high-strength natural gas foamed gel system by adding a gel system to the foaming agent solution. The Ostwald ripening rate and the gas molecular diffusion coefficient (D diff) were calculated. The number of bubbles, the average diameter­(D ad), and the poly-dispersion coefficient (U poly) of the foamed gel system have been considered within, as well as the different temperature, salinity, pressure, and crude oil conditions and the stability of the foamed gel system. Moreover, combining laboratory displacement experiments and core nuclear magnetic (NMR) experiments, the oil displacement ability of natural gas foamed gel was studied. The results showed that different from the previous phenomenon of “defoaming with oil”, adding a certain amount of crude oil into the natural gas foamed gel could improve its foaming performance. According to this phenomenon, we conducted experiments on the stability and viscosity enhancement of the emulsion and explored the stability of the pseudo-emulsion film of foamed gel. In addition, this natural gas foamed gel system had a better ability to control profile and enhance oil recovery when the permeability ratio was 75–150. When the permeability ratio was 150, the low-permeability core diversion rate was about 38%, and the EOR was 35.27%. Finally, the core NMR results showed that the main contribution of water flooding recovery came from macropores. In construct, the recovery efficiency of natural gas foamed gel system mainly came from medium and small pores (effective areas not affected by water flooding). This study would provide a different thought for foam in production while dealing with extreme heterogeneity formations.

Experimental Investigation of a Polymer-Enhanced N2 Foam Performance for Enhanced Oil Recovery

“…It was helpful to the necking and separation of bubbles and membrane breaking. 15 When the injection flow rate of foam was too large, the viscosity of foam would be reduced and its stability in porous media would worsen. Macroscopically, it showed that the mobility control ability in the rock core declined.…”

“…22,23 Finally, in the presence of crude oil, a polymer makes the emulsion formed by the surfactant and crude oil more stable, which can improve the strength of the pseudo-emulsion film, thus improving the oil resistance of the foam. 23 Many scholars have reported relevant studies on foam pseudo-emulsions, including N 2 foam, 24,25 natural gas foam, 15 CO 2 foam, 26 etc., which shows that basically all types of foam will form pseudo-emulsions, regardless of the type of gas. If the polymer is salt-resistant, it can improve the compatibility and durability of foam in environments with high salt concentrations.…”

“…Second, the polymer can not only enhance the viscoelasticity of the foam surface but also generate electrostatic attraction with the surfactant in the foam, which compacts the charge arrangement on the monolayer adsorption layer and increases the stability of the foam. , Third, with the formation of a polymer network structure in the foam liquid film and alteration of the internal morphology of the foam, the polymer can increase the stability of the foam. , Finally, in the presence of crude oil, a polymer makes the emulsion formed by the surfactant and crude oil more stable, which can improve the strength of the pseudo-emulsion film, thus improving the oil resistance of the foam . Many scholars have reported relevant studies on foam pseudo-emulsions, including N 2 foam, , natural gas foam, CO 2 foam, etc., which shows that basically all types of foam will form pseudo-emulsions, regardless of the type of gas. If the polymer is salt-resistant, it can improve the compatibility and durability of foam in environments with high salt concentrations .…”

“…The stability of foam propagating in porous media depends upon the formation and collapse of the liquid film. , As a result of the complex reservoir conditions, it is challenging for ordinary foams to maintain their strength when passing over porous media. In particular, the presence of crude oil can dramatically reduce the lifespan of foams. − Therefore, it is crucial to increase the stability of the foam in the reservoir. Numerous studies have demonstrated that adding stabilizers can considerably increase the strength and stability.…”

Evaluation of an Oxygen-Reduced Air Flooding Plugging System and Its Injection Method in the Honghe Oilfield

“…Some researchers have proposed that the addition of a cross-linking agent to the foam will generate foam and gel systems in the flow process and improve the foam stability. Therefore, Lai et al 20 used core flow experiments and nuclear magnetic resonance studies to analyze the improvement of core heterogeneity achieved by natural gas foam gel system flooding. Their results showed that natural gas foam gel mainly extracted crude oil within small pores.…”