Distinguishing the Effect of Rock Wettability from Residual Oil on Foam Generation and Propagation in Porous Media

Abstract

One of the common challenges of applying foam for enhanced oil recovery is the foam instability in the presence of crude oil and nonwater-wet surfaces. In this experimental study, we systematically distinguish the effect of rock surface wettability from that of crude oil saturation on foam rheology under reservoir conditions. Neutral-wet Berea and reservoir sandstone cores are prepared by aging with crude oil, followed by the wettability index measurements. Transient foam generation and steady-state foam quality scans are conducted in neutral-wet cores, with/without water-flood residual oil. Nuclear magnetic resonance imaging is also utilized to measure the remaining oil saturation at the end of the foam-flood. It is shown that strong foam can be generated in a neutral-wet core with no residual oil because of the solubilization of the adsorbed crude oil components and the wettability alteration toward more water-wet conditions. However, in a neutral-wet core containing residual oil, foam generation is initially hindered. Foam generation occurs after injecting several pore volumes of surfactant solution and increasing the superficial velocity to overcome the minimum pressure gradient required for in situ foam generation. The findings from this study suggest that surface wettability in the presence of bulk oil saturation significantly affects transient foam generation. The final steady-state foam strength becomes comparable to the water-wet and oil-free case once the residual oil saturation is adequately reduced.

Experimental Research on the Millimeter-Scale Distribution of Oil in Heterogeneous Reservoirs

“…Fannir et al [35] studied the experimental research on two-phase flow displacement using Magnetic Resonance Imaging (MRI) techniques and investided the process of the phase trapping, the front deformation and the phases saturation propagation along a vertical model during (water-oil) two-phase flow. Yadali Jamaloei et al [36][37][38] analyzed the effect of wettability on the microscopic oil displacement mechanism. Alyafei et al [39] took cores containing oil and a specified initial water saturation, injected water flooding until 10 pore volumes, and observed the relationship between the initial oil saturation and the residual saturation.…”

Experimental Evaluation of Foam-Assisted Gas Injection in Proppant-Packed Fractured Oil-Wet Carbonate

“…Permeability contrast defined as the ratio of the permeabilities of the fracture and matrix is another key parameter that significantly impacts the performance of foams among a large number of reservoir conditions such as rock wettability, − surface roughness, and mineralogy. Such investigations help identify superior chemicals or blends of chemicals for field applications and mitigate the risk by determining, for instance, the optimum range of surfactant concentrations at which a desirable foam performance is achieved for a given fractured medium.…”

Probing the Effect of Wettability on Transport Behavior of Foam for Enhanced Oil Recovery in a Carbonate Reservoir

“…It is reported that the foam strength in porous media is largely influenced by the surfactant type and concentration, reservoir property (salinity, hardness, temperature, wettability, oil saturation, permeability, heterogeneity, etc. ), − operational methods (flow rate, injection scheme, foam quality, etc. ), ,− gas type, − local capillary pressure, and foam texture. − Note that the foam steady state may indicate a balance between the lamellae creation rate and lamellae coalescence rate.…”

“…It is universally accepted that oil has a detrimental effect on the foam stability, especially when the oil sample contains a large amount of light components. ,, The destabilization effect of oil on the foam stability has been extensively investigated, and several criteria have been proposed to predict the stability of foam in the presence of oil. Among them, the most reliable theory may be based on the stability of the pseudoemulsion film, i.e., the pseudoemulsion film disjoining pressure. , The other theories to account for the oil destabilization effect include lamellae number and the entering/spreading/bridging coefficients, which are calculated based on the surface/interfacial tension .…”