Utilization mechanism of foam flooding and distribution situation of residual oil in fractured-vuggy carbonate reservoirs

The development of fractured-vuggy carbonate reservoirs is extremely difficult because of the complex fractured-vuggy structure and strong heterogeneity.Foam flooding is a potential enhanced oil recovery(EOR)technology in fractured-vuggy carbonate reservoirs.Based on the similarity criterion,three types of 2D visual physical models of the fractured-vuggy structure were made by laser ablation technique,and a 3D visual physical model of the fractured-vuggy reservoir was made by 3D printing technology.Then the physical analog experiments of foam flooding were carried out in these models.The experimental results show that foam can effectively improve the mobility ratio,control the flow velocity of the fluid in different directions,and sweep complex fracture networks.The effect of foam flooding in fractures can be improved by increasing foam strength and enhancing foam stability.The effect of foam flooding in vugs can be improved by reducing the density of the foam and the interfacial tension between foam and oil.Three types of microscopic residual oil and three types of macroscopic residual oil can be displaced by foam flooding.This study verifies the EOR of foam flooding in the fractured-vuggy reservoir and provides theoretical support for the application of foam flooding in fractured-vuggy reservoirs.

Influence of formation heterogeneity on foam flooding performance using 2D and 3D models:an experimental study

The formation heterogeneity is considered as one of the major factors limiting the application of foam flooding.In this paper,influences of formation properties,such as permeability,permeability distribution,interlayer,sedimentary rhythm and 3D heterogeneity,on the mobility control capability and oil displacement efficiency of foam flooding,were systematically investigated using 2D homogeneous and 2D/3D heterogeneous models under 120°C and salinity of 20×10~4 mg/L.The flow resistance of foam was promoted as the permeability increased,which thus resulted in a considerable oil recovery behavior.In the scenario of the vertical heterogeneous formations,it was observed that the permeability of the high-permeable layer was crucial to foam mobility control,and the positive rhythm appeared favorable to improve the foam flooding performance.The additional oil recovery increased to about 40%.The interlayer was favorable for the increases in mobility reduction factor and oil recovery of foam flooding when the low permeability ratio was involved.For the 3D heterogeneous formations,foam could efficiently adjust the areal and vertical heterogeneity through mobility control and gravity segregation,and thus enhancing the oil recovery to 11%–14%.The results derived from this work may provide some insight for the field test designs of foam flooding.

Hybrid surfactant-nanoparticles assisted CO_(2) foam flooding for improved foam stability:A review of principles and applications

Miscible carbon dioxide(CO_(2))flooding is a well-established and promising enhanced oil recovery(EOR)technique whereby residual oil is recovered by mixing with injected CO_(2)gas.However,CO_(2),being very light and less viscous than reservoir crude oil,results in inefficient sweep efficiency.Extensive research is ongoing to improve CO_(2)mobility control such as the development and generation of CO_(2)/water foams.The long-term stability of foam during the period of flooding is a known issue and must be considered during the design stage of any CO_(2)foam flooding project.The foam stability can be improved by adding surfactants as stabilizers,but surfactants generated foams have generally a shorter life because of an unstable interface.Furthermore,surfactants are prone to higher retention and chemical degradation in the porous media,particularly under harsh reservoir conditions.Research has shown that nanoparticles(NPs)can act as an excellent stabilizing agent for CO_(2)/water foams owing to their surface chemistry and high adsorption energy.The foams generated using NPs are more stable and provide better mobility control compared to surfactant-stabilized foams.One limitation of using NPs as foam stabilizers is their colloidal stability which limits the use of low-cost NPs.Combining surfactants and NPs for CO_(2)foam stabilization is a novel approach and has gained interest among researchers in recent years.Surfactants improve the dispersion of NPs in the aqueous phase and minimize particle aggregation.NPs on the other hand create a stable barrier at the CO_(2)/water interface with the help of surfactants,thus generating highly stable and viscous foams.This paper presents a comprehensive review of the basic principles and applications of stabilized CO_(2)foams.A brief overview of CO_(2)foam flooding is discussed first,followed by a review of standalone surfactant-stabilized and NPs-stabilized CO_(2)/water foams.The application of hybrid surfactant-NPs stabilized CO_(2)foams is then presented and areas requiring further investigation are highlighted.This review provides an insight into a novel approach to stabilize CO_(2)/water foams and the effectiveness of the method as proved by various studies.

The effect of nanosilica sizes in the presence of nonionic TX100 surfactant on CO_(2)foam flooding

The aim of this research is to study the effect of hydrophilic silica nanoparticles,sizes as CO_(2) foam stabilizer in the presence of nonionic TX100 surfactant.Two nanosilica sizes,15 and 70 nm,have been examined thoroughly.Physisorption of TX100 on silica nanoparticles(nanosilica)was characterized by adsorption isotherm and surface tension measurement,while CO_(2) foams stability was quantified based on their foamability,foam stability,particle partitioning in the foams,and bubble sizes.Results show that direct contact of TX100 with nanosilica does altered the wettability of hydrophilic nanosilica surface,enable them to lengthen CO_(2) foams life at certain surfactant and nanoparticles concentrations.For 15 nm nanosilica,CO_(2) foam stability shows excellent performance at 0.1 and 0.5 wt%TX100 concentrations.As for 70 nm nanosilica,CO_(2) foam demonstrates longer lifetime at much lower TX100 concentration,0.01 wt%.Without the presence of TX100,CO_(2) foams exhibit undesirable lifetime performances for both nanosilica sizes.Nanosilica partitioning in CO_(2) foams structures demonstrate consistent relation with contact angle measurement.Estimated bubble sizes shows insignificant effect on CO_(2) foams life.With the assists of nanosilica and TX100,enhanced oil recovery via CO_(2) foam injection succeeds in increasing oil production by 13e22%of original oil-in-place(OOIP).

Gas/water foams stabilized with a newly developed anionic surfactant for gas mobility control applications

Carbon dioxide(CO2) flooding is one of the most globally used EOR processes to enhance oil recovery.However,the low gas viscosity and density result in gas channeling and gravity override which lead to poor sweep efficiency.Foam application for mobility control is a promising technology to increase the gas viscosity,lower the mobility and improve the sweep efficiency in the reservoir.Foam is generated in the reservoir by co-injection of surfactant solutions and gas.Although there are many surfactants that can be used for such purpose,their performance with supercritical CO2(ScCO2) is weak causing poor or loss of mobility control.This experimental study evaluates a newly developed surfactant(CNF) that was introduced for ScCO2 mobility control in comparison with a common foaming agent,anionic alpha olefin sulfonate(AOS) surfactant.Experimental work was divided into three stages:foam static tests,interfacial tension measurements,and foam dynamic tests.Both surfactants were investigated at different conditions.In general,results show that both surfactants are good foaming agents to reduce the mobility of ScCO2 with better performance of CNF surfactant.Shaking tests in the presence of crude oil show that the foam life for CNF extends to more than 24 h but less than that for AOS.Moreover,CNF features lower critical micelle concentration(CMC),higher adsorption,and smaller area/molecule at the liquid-air interface.Furthermore,entering,spreading,and bridging coefficients indicate that CNF surfactant produces very stable foam with light crude oil in both deionized and saline water,whereas AOS was stable only in deionized water.At all conditions for mobility reduction evaluation,CNF exhibits stronger flow resistance,higher foam viscosity,and higher mobility reduction factor than that of AOS surfactant.In addition,CNF and ScCO2 simultaneous injection produced 8.83% higher oil recovery than that of the baseline experiment and 7.87% higher than that of AOS.Pressure drop profiles for foam flooding using CNF was slightly higher than that of AOS indicating that CNF is better in terms of foam-oil tolerance which resulted in higher oil recovery.

A contrasting analysis of CO_(2)and N_(2)foam flood for enhanced oil recovery and geological storage of CO_(2)

Foam flooding using CO_(2)has emerged as a promising method for both enhanced oil recovery(EOR)and the storage of CO_(2)in geological reservoirs.This study conducts a thorough analysis of the behavior of CO_(2)and N_(2)foams in bulk and porous media,utilizing bubble-scale analyses and foam flooding experiments.The study compares the foamability and longevity of CO_(2)and N_(2)foams,with findings indicating that N_(2)foam bubbles tend to be smaller and less varied in size than CO_(2)foam bubbles,leading to increased foam stability.Additionally,the study compares the half-lives of CO_(2)and N_(2)foams generated through sparging and winding methods,showing that N_(2)foam has half-lives 22 and 10 times greater than CO_(2)foam when produced using the sparging and winding methods,respectively.Furthermore,CO_(2)foam generated through the sparging method had a lower foaming volume than N_(2)foam due to CO_(2)'s solubility.In the foam flooding experiments,N_(2)foam proved more effective in recovering oil from porous media than CO_(2)foam,thus demonstrating the effectiveness of the foam injection procedure.These results offer valuable insights into the differing performance of N_(2)and CO_(2)foam floods for EOR and CO_(2)geological storage.