Interfacial Tension Foam Research Articles

Experimental study of ultra-low IFT foam flooding for low permeability reservoirs

Foam flooding is an effective oil displacement technique to improve fluid sweep efficiency and increase oil recovery. The objective of this paper is to investigate the applicability of ultra-low IFT foam flooding for low permeability oil recovery under the conditions of WX reservoir block in Tuha oilfield (84°C, 86,072 mg/L). A modified amphoteric hydroxy sulfobetaine surfactant (Cn-HSB) was formulated as a foaming agent based on the principle of compatibility with crude oil that could achieve the ultra-low interfacial tension (IFT) and strong foamability simultaneously. This is shown to reduce the oil/water dynamic IFT (DIFT) to an ultra-low value of the order of 10−5 mN/m (0.10wt%), as well as produce a foam volume and half-life of 448 mL and 2567 s, respectively. In addition, results of IFT and foam quality tests indicate that the modified Cn-HSB has good thermal stability and excellent salinity-resistance. Moreover, the ultra-low IFT foam flooding has an ideal injectivity and oil displacement efficiency in low permeability porous media that can mobilize the trapped oil in k = 1.50 × 10−3μm2 with a threshold pressure gradient of 0.115 MPa/m. This improves oil displacement efficiency about 15%OOIP. Fundamental knowledge gained from this research gives insight into the application of ultra-low IFT foam flooding in low-permeability reservoirs under a combination of specific reservoir conditions.

Research on EOR for ultralow interfacial tension foam in high-temperature and high-salinity reservoirs: flooding simulation and application in Shengli Oilfield

For high temperature and high salinity reservoirs, the foam formulation system is required to have better foaming capacity and foam stability under formation conditions in tertiary EOR. In order to obtain a new foam agent suitable for this type of oil reservoir, through the compounding and testing of 7 common oilfield foam chemical agents, 15 formulated foam agents are tested and screened. Then the foam displacement experiment of the dual sand packs model was established to simulate the new foam flooding process. The production dynamic of the high-permeability sand pack and the low-permeability sand pack was captured and analyzed, and EOR mechanism of the foam system in the heterogeneous reservoir was clarified. The experimental results show that the formulation of B4(anionic & nonionic combined surfactant) & FSN100(fluorinated surfactant) with a mass proportion of 2:3 (BF23) has the best performance in terms of foaming properties, low interfacial tension reduction, and oil washing efficiency. Furthermore, BF23 foam injection greatly increased the recovery factor from 36.7% to 61.6%, clearly displacing the remaining oil in the low-permeability pack. Finally, the new foam agent solution used in Shenger block of Shengli Oilfield shows its good value for enhanced oil recovery.

The study of ultralow interfacial tension SiO2-surfactant foam for enhanced oil recovery

Surfactant selection and formulation are key factors in technological and economic success in chemically enhanced oil recovery (cEOR) applications. In this study, the silica nanoparticle (SNP) was added in an ultralow interfacial tension foam (ULIFT), called SNP-ULIFT foam, which was successfully prepared by ternary surfactant systems. The Carboxylate-based extended surfactant (Carboxylate), Dioctyl Sulfosuccinate Sodium salt (AOT), and Sodium Diphenyl Oxide Disulfonate (DODS) at a 0.48:0.48:0.04 wt ratio were conducted as the surfactant system. Remarkable results in the selected surfactant system were observed in terms of the ability to form foaming and ultralow interfacial tension (IFT) at 60 ± 2 °C with the ADNOC crude oil (Abu Dhabi National Oil Company) as model oil. The optimum salinity of the surfactant system was found at 2.5 wt% (8:2 Na:Ca by weight), indicating a minimum IFT of 0.0019 mN/m. The adsorption capacities at the optimum salinity condition of each surfactant in the mixture onto the SNP's surface were 1.4, 7.3 and 19.4 molecule/nm2 for the DODS, Carboxylate and AOT surfactants, respectively; the calculated total surfactant adsorption was 2.6 mg surfactant/mg nanoparticles. While in the presence of SNP, the surfactant adsorption of the ternary surfactant foam system onto the sand surface was significantly reduced by 16.2% at 200 psi and 60 °C when compared with the neat ULIFT foam system. It was remarkably noted that the adsorption of the surfactant onto the SNP surface could result in a reduction of surfactant adsorption onto the sand surface. The oil recovery performance in the core flood by ULIFT foam was the greatest with 43% of Original Oil in Place (OOIP), and it further increased by 13% in the presence of 200 ppm SNP. In addition, the stress and viscosity of ULIFT microemulsion significantly decreased with SNP. This suspension exhibited the most non-Newtonian behavior with shear-thinning behavior over different ranges of shear rate. Therefore, SNP-ULIFT foam with the appropriate surfactant selection was a successful method for improving oil recovery performance.

Research on Evaluation Method of Ultralow Interfacial Tension Foam for High-Temperature and High-Salinity Reservoirs: A Field Case in Shengli Oilfield, China

Research on Evaluation Method of Ultralow Interfacial Tension Foam for High-Temperature and High-Salinity Reservoirs: A Field Case in Shengli Oilfield, China

Ultralow-Interfacial-Tension Foam-Injection Strategy in High-Temperature Ultrahigh-Salinity Fractured Oil-Wet Carbonate Reservoirs

Summary Oil recovery in many carbonate reservoirs is challenging because of unfavorable conditions, such as oil–wet surface wettability, high reservoir heterogeneity, and high brine salinity. We present the feasibility and injection–strategy investigation of ultralow–interfacial–tension (IFT) foam in a high–temperature (greater than 80°C), ultrahigh–formation–salinity [greater than 23% total dissolved solids (TDS)] fractured oil–wet carbonate reservoir. Because a salinity gradient is generated between injection seawater (SW) (4.2% TDS) and formation brine (FB) (23% TDS), a frontal–dilution map was created to simulate frontal–displacement processes and thereafter it was used to optimize surfactant formulations. IFT measurements and bulk–foam tests were also conducted to study the salinity–gradient effect on the performance of ultralow–IFT foam. Ultralow–IFT foam–injection strategies were investigated through a series of coreflood experiments in both homogeneous and fractured oil–wet core systems with initial oil/brine two–phase saturation. The representative fractured system included a well–defined fracture by splitting the core sample lengthwise. A controllable initial oil/brine saturation in the matrix can be achieved by closing the fracture with a rubber sheet at high confining pressure. The surfactant formulation achieved ultralow IFT (magnitude of 10−2 to 10−3 mN/m) with the crude oil at the displacement front and good foamability at underoptimal conditions. Both ultralow–IFT and foamability properties were found to be sensitive to the salinity gradient. Ultralow–IFT foam flooding achieved more than 50% incremental oil recovery compared with waterflooding in fractured oil–wet systems because of the selective diversion of ultralow–IFT foam. This effect resulted in a crossflow near the foam front, with surfactant solution (or weak foam) primarily diverted from the fracture into the matrix before the foam front, and oil/high–salinity brine flowing back to the fracture ahead of the front. The crossflow of oil/high–salinity brine from the matrix to the fracture was found to create challenges for foam propagation in the fractured system by forming Winsor II conditions near the foam front and hence killing the existing foam. It is important to note that Winsor II conditions should be avoided in the ultralow–IFT foam process to ensure good foam propagation and high oil–recovery efficiency. Results in this work contributed to demonstrating the technical feasibility of ultralow–IFT foam in high–temperature, ultrahigh–salinity fractured oil–wet carbonate reservoirs and investigated the injection strategy to enhance the low–IFT foam performance. The ultralow–IFT formulation helped to mobilize the residual oil for better displacement efficiency and reduce the unfavorable capillary entry pressure for better sweep efficiency. The selective diversion of foam makes it a good candidate for a mobility–control agent in a fractured system for better sweep efficiency.

Ultra-Low Interfacial Tension Foam System for Enhanced Oil Recovery

The liquid phase of foam systems plays a major role in improving the fluidity of oil, by reducing oil viscosity and stripping oil from rock surfaces during foam-flooding processes. Improving the oil displacement capacity of the foam’s liquid phase could lead to significant improvement in foam-flooding effects. Oil-liquid interfacial tension (IFT) is an important indicator of the oil displacement capacity of a liquid. In this study, several surfactants were used as foaming agents, and polymers were used as foam stabilizers. Foaming was induced using a Waring blender stirring method. Foam with an oil-liquid IFT of less than 10–3 mN/m was prepared after a series of adjustments to the liquid composition. This study verified the possibility of a foam system with both an ultra-low oil-liquid IFT and high foaming properties. Our results provide insight into a means of optimizing foam fluids for enhanced oil recovery.

Experimental Study on Low Interfacial Tension Foam for Enhanced Oil Recovery in High-Temperature and High-Salinity Reservoirs

Foam flooding is an important method to enhance oil recovery after water flooding. In this paper, a novel low interfacial tension (LIFT) nitrogen foam was successfully prepared by an amphoteric surfactant and sodium formate. It has good foaming ability and can reduce interfacial tension to a low interfacial tension level (10–1 mN/m order of magnitude) in high-temperature (90 °C) and high-salinity (183 g/L salinity) reservoirs. The influence of surfactant concentration, organic bases concentration, and aging on the performances of the LIFT foam system has been systematically studied through the modified Ross-Miles experiment. Furthermore, the foam displacement in flat-panel sand model and etched-glass micromodels were conducted to investigate the foam displacement mechanisms for enhanced oil recovery. The results of flat-panel sand model experiment showed that the LIFT foam could block high permeability channels and divert following injection fluid to adjacent low permeability areas efficiently. Meanwhile, with the injection of the LIFT foam, the injection pressure of the whole model continued to increase, and the pressure distribution was more uniform. The etched-glass micromodels experiment results showed that the LIFT foam could block the high permeability channels and improve sweep efficiency. Furthermore, comparing with the common foam, the LIFT foam could emulsify oil and strip oil film from model surfaces more easily. So it could enhance the oil recovery more efficiently.

Optimization and evaluation of binary composite foam system with low interfacial tension in low permeability fractured reservoir with high salinity

The foam flooding technology can be used in low permeability fractured reservoir for tertiary oil recovery. In view of low permeability fractured reservoir with low temperature and high salinity, a binary composite low interfacial tension foam system is developed, and the composite foaming ability, interfacial tension, resistance to oil, salt and temperature of the foam system were evaluated in this paper, and then the plugging ability and oil displacement efficiency were studied. It is indicated that under the condition of 32 °C and 29 500 mg/L formation water salinity the optimized formulation of binary composite low interfacial tension foam system is selected for 0.12% W fluorocarbon foamer+0.08% QL betaine +0.1% BS betaine +1500 mg/L polymer; for the reservoir with big permeability difference existed between layers or high permeability reservoir, profile control measures are needed to be further taken before foam injection; 0.4 PV foam system and 0.1 PV profile control system were injected into the parallel core column with high permeability 1000mD and low permeability 10mD cores in the oil displacement experiment, and the recovery of low permeability core was enhanced by 18.87%. In practical application, the profile control system and its amount need to be optimized according to the actual situation.

Investigation of certain physical\u2013chemical features of oil recovery by an optimized alkali\u2013surfactant\u2013foam (ASF) system

The objective of this study is to discover a synergistic effect between foam stability in bulk and micro-emulsion phase behaviour to design a high-performance chemical system for an optimized alkaline–surfactant–foam (ASF) flooding for enhanced oil recovery (EOR). The focus is on the interaction of ASF chemical agents with oil in the presence and absence of a naphthenic acid component and in situ soap generation under bulk conditions. To do so, the impact of alkalinity, salinity, interfacial tension (IFT) reduction and in situ soap generation was systematically studied by a comprehensive measurement of (1) micro-emulsion phase behaviour using a glass tube test method, (2) interfacial tension and (3) foam stability analysis. The presented alkali–surfactant (AS) formulation in this study lowered IFT between the oil and aqueous phases from nearly 30 to 10−1–10−3 mN/m. This allows the chemical formulation to create considerably low IFT foam flooding with a higher capillary number than conventional foam for displacing trapped oil from porous media. Bulk foam stability tests demonstrated that the stability of foam diminishes in the presence of oil with large volumes of in situ soap generation. At lower surface tensions (i.e. larger in situ soap generation), the capillary suction at the plateau border is smaller, thus uneven thinning and instabilities of the film might happen, which will cause acceleration of film drainage and lamellae rupture. This observation could also be interpreted by the rapid spreading of oil droplets that have a low surface tension over the lamella. The spreading oil, by augmenting the curvature radius of the bubbles, decreases the surface elasticity and surface viscosity. Furthermore, the results obtained for foam stability in presence of oil were interpreted in terms of phenomenological theories of entering/spreading/bridging coefficients and lamella number.

A new laboratory study on alternate injection of high strength foam and ultra-low interfacial tension foam to enhance oil recovery

Ultimate oil recovery depends on both macro sweeping efficiency and micro displacement efficiency. Foam flooding is an important method to enhance oil recovery (EOR) after water flooding. Composed of one surfactant, a traditional foaming agent generates stable foam with gas or air to block high-permeable swept zones and to improve the sweeping efficiency without significantly improving displacement efficiency. In this paper, we present a newly designed technology of alternate flooding through high strength foam (HSF) and ultra-low interfacial tension foam (ULT) to enhance oil recovery. HSF foam generates large, stable bubbles in presence of oil, beneficial to block high permeability areas; ULT foam generates small bubbles and reduces the oil-water interfacial tension to ultra-low grade. In the experiments of three parallel sand packs, the HSF foam generated with surfactant GINF-1/air could block the large pores and improve sweeping efficiency, and the ULT foam generated with surfactant LINF-2/air could improve the displacement efficiency in swept zones after water flooding. Both experimental results in parallel sand pack and 3-D sand pack show that the HSF and ULT foam alternate flooding can improve not only sweeping efficiency but also micro oil displacement efficiency, and the foam alternate flooding can realize a high oil recovery than HSF or ULT foam flooding separately. The experimental study also shows that the two foams should be alternatively injected in foam flooding of heterogeneous reservoirs, in a sequence is that HSF foam slug is applied first before using the ULT foam slug. Moreover for a given total volume of foam, a higher oil recovery is obtained through properly decreasing the volume of each foam slug and increasing the number of alternate stages.

Foam Flooding with Ultra-Low Interfacial Tension to Enhance Heavy Oil Recovery

Severe viscous fingering during water flooding of heavy oil leaves a large amount of oil untouched in the reservoir. Improving sweep efficiency is vital for increasing heavy oil recovery. Previous researches have proved that foam flooding can increase the sweep efficiency and oil recovery. The polymers could make the foam more stable and have better plugging capacity, but the interfacial tension (IFT) of oil and water increase which could decrease the displacement efficiency of the heavy oil. In view of the deficiency of conventional foam flooding, it is necessary to research the ultra-low interfacial tension foam which could improve macro-swept volume and micro-displacement efficiency in heavy oil reservoir. In this paper a novel foam agent is developed by the combination of surfactant and additives to lower the IFT of oil and water. The operating parameters including foam injections modes and gas liquid ratio were investigated by core flooding experiments. Field test performance shows that oil production per day increased from 85.6 to 125.7 t, water cut declined from 92.1 to 83.6% after 3 months injection. This study provides a novel method to improve heavy oil recovery with an ultra-low interfacial tension foam flooding system.

The Laboratory Research on Ultra-Low Interfacial Tension Foam Flooding System with High-Temperature and High-Salinity

To obtain the ultra-low interfacial tension foam flooding system for the real reservoir condition of high-temperature and high-salinity, foam properties and dynamic interfacial tension had been performed by Ross-miles test and spin drop tension meter respectively. Ten types of surfactants were screened by foamability, stability and interfacial tension (IFT) at 85°C, high-salinity with 800 mg/L divalent cations and 30000 mg/L total mineralization. The AOS, AESO and 20YB were selected to compose further anion-nonionic mixture system. Due to AOS had excellent foam properties, AESO could achieve low interfacial tension and 20YB could improve the film quality. Through series complex study, the ultra-low interfacial tension (10-4mN/m order of magnitude) foam system was obtained with the composition of 0.15%wtAOS+0.15%wtAESO+0.11%~0.012%wt20YB for high-temperature and high-salinity, which V foam was 240-235 mL and t0.5was 180-190 min. In addition, the synergistic effect of these surfactants had been described.

Successful Test of the First Ultralow Interfacial Tension Foam Flood

This article is a synopsis of paper SPE 72147, "Successful Field Test of the First Ultralow Interfacial Tension Foam Flood," by Wang Demin, SPE, Cheng Jiecheng, SPE, Yang Zhenyu, Li Qun, SPE, Wu Wenxiang, SPE, and Yu Huiyu, SPE, Daqing Oil Co. Ltd., originally presented at the 2001 SPE Asia Pacific Improved Oil Recovery Conference, Kuala Lumpur, 8-9 October.