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CO2mobility control in porous media is crucial to geological sequestration of CO2and enhanced oil recovery (EOR). Although aqueous foam has been widely used to control the mobility of CO2, bubble dispersion with low gas content is formed easily because of gas–liquid separation caused by gravity differentiation, which reduces the storage volume of CO2and limits its utilization. In this work, the use of armored bubbles with silica nanoparticles for CO2mobility control in porous media was explored. Visual micromodel flooding experiments were conducted to study the pore-scale flow behaviors of bubbles. Both homogeneous and heterogeneous flooding experiments were used to evaluate the mobility control ability of bubble dispersions. The results showed that the nanoparticles were adsorbed on the interface of CO2bubbles and formed an armor layer, which made the interface more solid-like and enhanced the roughness of the bubble film. Subsequently, the effective viscosity of the armored CO2bubble dispersions increased and showed a shear-thinning property. By observing the pore-scale flow behaviors, it was found that armored bubbles showed high rigidity and strong plugging ability, thereby trapping CO2in porous media and enlarging the sweep region. A synergistic plugging effect occurred between the armored bubbles, which drove the subsequent bubbles to invade into the residual oil region. Moreover, as the armored bubbles became rough, the residual oil was activated more easily by the scraping effect, and the oil-transporting ability of bubbles was enhanced. Thus, residual oils formed after water flooding could be displaced by armored bubbles thoroughly. In homogeneous porous media, the breakthrough and flow channels of the displacing fluid were controlled by the strong plugging of armored bubbles in porous media, and the displacement efficiency was enhanced. The ultimate oil recovery of armored bubble flooding was improved by about 11.4% compared to that of bare surfactant bubble flooding. In heterogeneous porous media, the mobility of the displacing fluid in relatively high permeability sandpack was reduced more effectively by armored bubbles. Even during the subsequent water flooding stage, the armored bubbles showed relatively strong resistance to water erosion and inhibited the differentiation of outflow percentage. Therefore, the flow profile was controlled by armored bubbles, and the ultimate oil recovery was improved by about 14.3% using armored bubbles. The results confirmed the high mobility control performance of nanoparticle-armored bubbles for EOR.

Carbon dioxide (CO2) is injected into reservoirs for enhanced oil recovery worldwide, which is an important technology to reduce carbon emissions from burning and consumption of fossil fuels. However, it is difficult to control the mobility of carbon dioxide in the formation, thus limiting its extensive utilization. In this work, particulate matter (PM) from flue gas was used to obtain an interfacial armored foam for controlling the CO2mobility in porous media. Both homogeneous and heterogeneous porous model experiments were adopted to study CO2foam flow behavior in porous media. Furthermore, the viscosity, interfacial viscoelasticity, and microstructure of foam were measured to help understand the mobility control mechanism. The results showed that the interfacial adsorption and compression of PM formed a particle armor on the CO2-liquid interface, which improved foam film roughness and changed the interface to be more solid-like. Consequently, the viscosity of CO2foams was increased by 2–13 times with the addition of 1.2 wt. % PM. In pore scale, the PM armored foams had stronger Jamin resistance and slipping resistance than bare surfactant foam. Thus, they showed relatively low mobility in porous media. The CO2gas channel and water breakthrough were inhibited by the injection of 1 PV armored foams. The armored foams showed a higher resistance to the water flushing during the subsequent water flooding. The use of bare PM dispersions did not establish an effective flow resistance in the porous media. However, when a lower CO2content (20% foam quality) was co-injected with the liquid phase, the improvement of foam resistance factor by adding PM was about 3 times upon addition of PM. Moreover, in the heterogeneous porous model, the mobility of fluids in the high permeability sandpack was effectively controlled by the armored foam, thus increasing the sweeping efficiency in the medium and low permeability sandpacks. Compared with bare surfactant foam flooding, the oil recovery by using armored foam was increased by about 21.3%. After flooding with armored foams, the residual resistance factors of armored foams were reduced to a lower level by enough subsequent water flooding, indicating the temporary plugging and low damage of armored foams in porous media. The significance of this research is the utilization of two important atmospheric pollutants by an inexpensive Pickering foam method for petroleum development and carbon sequestration.

Carbon dioxide (CO2) foam flooding is a promising carbon capture, utilization, and storage technology that is often used for enhanced oil recovery (EOR). However, the instability of foam and low displacement efficiency restrict its efficient utilization. In this work, the microflow behavior and the EOR performance of aqueous CO2foam stabilized by particulate matter (PM) from coal combustion were systematically studied using a micromodel with etched porous media. The results showed that, when a moderate camellia oleifera saponin (COS) concentration was used, the addition of PM could transfer the maximum foam volume to a higher temperature. Moreover, with the addition of PM, the half-life of CO2foam drainage could be increased by ∼12 times at 75 °C. The disproportionation, coalescence, and film rupture of CO2foams in the porous media slowed down in the presence of PM. At high water cut stage, the different types of microresidual oil, such as cluster, columnar, membrane, and blind-end, could effectively be activated and displaced by the PM/COS foam. During the flooding, the high stability of PM/COS foam in the presence of oil guaranteed the efficiency of the whole process. The solid-like foam film enhanced the plugging effect in the water channel. The rough surface of the PM/COS bubble with high interfacial viscoelasticity enhanced the scrubbing capacity of the bubble to residual oil. According to the sandpack flooding results, the recovery of oil increased by ∼40.85% due to the injection of PM/COS foam and subsequent water at 60 °C, which was about twice of the oil recovery obtained using pure surfactant foam.

Successful enhancement of heavy oil and bitumen production using CO2-based enhanced oil recovery (EOR) techniques requires extensive knowledge about the diffusivity of CO2in heavy crudes. In this work, two advanced correlative approaches, namely group method of data handling (GMDH) and gene expression programming (GEP), were utilized to establish simple-to-use mathematical correlations by applying a comprehensive dataset including 260 laboratory data of CO2diffusion coefficient (DC) in heavy crudes and taking into account all the parameters affecting the accuracy of the models. Moreover, the response surface and contour plots were analyzed to obtain the desired response values and operating conditions. The GMDH correlation represented more reliable results with better statistical criteria including average absolute percentage error (AAPRE) values of 7.47%, 7.83%, and 7.54% for training, testing, and the total sets, respectively. Also, the results showed that the increase in pressure and/or temperature caused an increment in the amount of diffusivity of CO2in heavy crudes; and the maximum amount of CO2DC was obtained at the upper limit of these operational parameters. At a given temperature and pressure, it appears that the highest CO2DC in heavy crudes was obtained when the CO2mass fraction was less than 0.02. Furthermore, the Pearson and Spearman correlation coefficients were used to investigate linear and non-linear relationships between input variables and the responses of GMDH and GEP correlations. The mass fraction of CO2, temperature, pressure, and temperature_PVT had a direct relationship, and on the other hand, the viscosity and density of crudes had a reverse relationship with CO2DC. Finally, the reliability of the data bank of CO2DC in heavy crudes along with the high validity of GMDH and GEP correlations was verified by the leverage technique. Notably, no out-of-leverage data were identified, with only seven and five data points considered as suspected for GMDH and GEP models, respectively.

The use of CO2as a fracturing fluid for reservoir stimulation to enhance oil and gas recovery in low-permeability formations is widespread. However, during the CO2injection process, the low viscosity of supercritical CO2(SC-CO2) at high temperature and pressure conditions usually causes serious fluid loss in porous media, thus restricting its efficient utilization. In this work, the dynamic filtration control properties of nanoparticle-enhanced dry SC-CO2foams in porous media were explored, and the effects of nanoparticle and surfactant concentration, foam quality, pressure drop, temperature, and permeability were systematically studied. The results showed that the SC-CO2/liquid interfacial viscoelasticity modulus and the corresponding foam viscosity were improved by the adsorption of silica nanoparticles at the SC-CO2/liquid interface. At high foam quality (⩾90%), the nanoparticles reduced the amount of coarse bubbles and prevented bubble disproportionation, both of which helped to maintain a higher viscosity in the ultradry foam. The nanoparticles also significantly enhanced the foam filtration control performance; compared to bare dioctyl sodium sulfosuccinate (AOT) foam, the total filtration coefficient of CO2was decreased by a factor of about 2.2–6.5 with an increase in SiO2nanoparticle concentration from 0.5 to 1.5 wt %. The effect of surfactant concentration on the filtration of foam with nanoparticles also correlated well with its effect on interfacial viscoelastic modulus and foam viscosity. Increasing the foam quality from 80 to 97% only increased the filtration control performance to a certain extent, as the foams became ultradry and unstable if the foam quality was too high (⩾90%); thereafter, a continuing increase in foam quality caused by CO2expansion at high pressure drop values led to low flow resistance and weakened the filtration control performance. The addition of silica nanoparticles reduced the temperature dependence of the foam filtration coefficient. The permeability and total filtration coefficient followed a power law relationship, with the addition of nanoparticles causing a decrease in the power law exponent. Return permeability tests after filtration result confirmed that nanoparticle-enhanced dry SC-CO2foams were relatively clean fluids for porous media.