Foam-Assisted Chemical Flooding for Enhanced Oil Recovery: Effects of Slug Salinity and Drive Foam Strength

Abstract

The novel enhanced oil recovery (EOR) technique combining the reduction of oil/water (o/w) interfacial tensions (IFT) to ultralow values and generation of a foam drive for mobility control is known as foam-assisted chemical flooding (FACF). We present a well-controlled laboratory study on the feasibility of FACF at reservoir conditions. Two specially selected chemical surfactants were screened on their stability in sea water at 90 °C. The ability of both surfactants to generate stable foam in bulk was studied in the presence and absence of crude oil. It led to the composition of the foam drive formulation for drive mobility control. Phase behavior scan studies, for the two crude oil/surfactant/brine systems, yielded the design of the chemical slug capable of mobilizing residual oil by drastically lowering the o/w IFT. Core-flood experiments were performed in Bentheimer sandstones previously brought to a residual oil to waterflood of 0.33 ± 0.02. A surfactant slug at under-optimum (o/w IFT of 10 −2 mN/m) or optimum (o/w IFT of 10 −3 mN/m) salinity was injected for mobilizing residual oil. It resulted in the formation of an unstable oil bank because of dominant gravitational forces at both salinities. Next, a foam drive was generated either in situ, by co-injecting nitrogen gas and surfactant solution, or pregenerated ex situ and then injected to displace the oil bank. We found that (i) the presence of the crude oil used in this work has a detrimental effect on foam stability in bulk and foam strength in Bentheimer sandstones, (ii) optimum salinity FACF was able to increase the ultimate oil recovery with 5% of the oil in place (OIP) after water flooding compared with under-optimum FACF, and (iii) injection of pregenerated drive foam increased its ultimate oil recovery by 13% of the OIP after water flooding compared to in situ drive foam generation at optimum salinity.

Perspectives in Nanocellulose for Crude Oil Recovery: A Minireview

“…A relatively new method known as foam-assisted chemical flooding (FACF) uses a surfactant plug to reduce water–oil IFT, followed by a foam drive to control oil mobility in reservoirs. The FACF process requires stable surfactants and foams, resilient to salinity and high-temperature conditions, and antifoaming agents (hydrocarbons) in the crude oil. ,, In EOR using FACF, the increased viscosity of the displacing phase as a result of bubbles combined with the ability of the surfactant to decrease IFT is used to increase both the macroscopic sweep/displacement efficiency of the reservoir and the microscopic oil displacement efficiency. Cellulose nanofibers containing lignin segments (CNF–L, 0.1 wt %, with 4–15 wt % lignin and 1.12–1.35 wt % COOH) mixed with surfactants [0.4 wt %, alkyl polyglycoside (APG) and α-olefin sulfonate (AOS)] exhibited reduced foam drainage rates, up to 5 times, in contrast with the surfactant alone .…”

Screening High-Temperature Foams with Microfluidics for Thermal Recovery Processes

“…However, PVT cells do not provide the porescale confinement inherent to reservoirs . Coreflood foam testing enables the assessment of foam performance by flowing the foam through a core plug and measuring the corresponding pressure drop across the porous medium . The measured pressure drop is then converted to a mobility reduction factor (MRF), a criterion intended to indicate foam efficacy, inclusive of permeability reduction and improved conformance.…”

“…Conventional coreflood testing is more representative of the actual in situ process, including both confinement and flow conditions. − However, its high operational cost and long runtime limits its practicality to rapidly and efficiently screen foam surfactants, imposing a barrier for operators facing with a wide range of commercial chemistries, each at a range of concentrations. Furthermore, the increase in pressure drop measured may not indicate desired foam performance but rather the pressure drop increase can be due to undesired fluid interactions such as sample incompatibility, salt precipitation as a result of brine content in the reservoir fluids and surfactant chemistry, and surfactant degradation at high temperature, the result of which can be permanent reservoir damage and negatively impact oil production and project economics.…”

“…9 Coreflood foam testing enables the assessment of foam performance by flowing the foam through a core plug and measuring the corresponding pressure drop across the porous medium. 10 The measured pressure drop is then converted to a mobility reduction factor (MRF), a criterion intended to indicate foam efficacy, inclusive of permeability reduction and improved conformance. Conventional coreflood testing is more representative of the actual in situ process, including both confinement and flow conditions.…”

Mechanistic Modeling of Water-Alternating-Gas Injection and Foam-Assisted Chemical Flooding for Enhanced Oil Recovery

“…Foam-assisted chemical flooding (FACF) combines the injection of a surfactant slug, for mobilizing residual oil, with foam generation for drive mobility control, thus obtaining favorable sweep efficiency. ,,− In a well-designed FACF, the surfactant slug provides an ultralow o/w IFT and adequately low slug mobility, mobilizing previously trapped residual oil and thus leading to the development of an oil bank. Surfactant slug mobility, which is a function of its viscosity and relative permeability, is relevant as it controls the part of the reservoir being contacted by the slug, determining the amount of oil that can potentially be mobilized from the reservoir.…”