A New Effective Multiwalled Carbon Nanotube-Foam System for Mobility Control

Abstract

Summary Nanoparticles have improved a surfactant's ability to create long-lasting foam. Recent studies have widely recommended the use of silica nanoparticles to enhance foam stability. This paper presents an experimental investigation of a new and highly effective alpha olefin sulfonate (AOS)–multiwalled carbon nanotube (MWCNT) system for mobility control during gas enhanced oil recovery (EOR) operations. The new AOS–MWCNT system was evaluated for its foam stability at 150°F using a high-pressure view cell. The MWCNT was obtained as solid particles of aspect ratio up to 100 and silica nanoparticles of median size of 118 nm. The foam system was optimized for its maximum half-life by varying the concentration of the AOS and the nanotube from 0.2 to 1% and 250 to 1,000 ppm, respectively. Compatibility testing with salts was done as well. Coreflood experiments with 1.5-in.-diameter, 6-in.-long Berea sandstone cores were run to calculate the mobility reduction factor at 150°F. Nitrogen foam was injected into the core at 80% foam quality in the tertiary recovery mode, and the pressure drop across the core was measured. The formation brine had a salinity of 5 wt% sodium chloride (NaCl), and the foaming solutions were prepared with 2 wt% NaCl. The optimal concentrations of the AOS solution and the nanotubes for maximum foam stability were determined to be 0.5% and 500 ppm, respectively. The optimized AOS–MWCNT system yielded 60% greater nitrogen foam half-life (32 minutes) than an optimized AOS–silica system at 150°F. The foam half-life of a stand-alone 0.5% AOS solution was 7 minutes. In the presence of crude oil, the foam half-life decreased for all the tested systems. Coreflood experiments at 150°F showed a significant increase in the mobility reduction factor when the new AOS–MWCNT system was used as the foamer instead of stand-alone AOS or AOS–silica system. The new foaming system was stable through the duration of the experiment, yielding foam in the effluent samples. There was no formation damage observed. Salt tolerance for the MWCNT nanofluid was higher than the silica nanofluid. Foam needs to be stable for long periods of time to ensure effective mobility control during gas injection for EOR. This paper investigates a new highly effective AOS-multiwalled carbon nanotube system that outperforms the AOS–silica foaming systems in terms of foam stability and mobility control at 150°F.

Nanofluid-Based Foam for Enhanced Oil Recovery in Fractured Carbonates

“…Improved conformance control by foam was also reported with organic NPs such as ethyl cellulose (EC), carbon nanodots (CND), graphene oxides (GOs), and multiwalled carbon nanotube (MWCNT) . For instance, EC/nonionic surfactant blends generated robust foams in a fractured carbonate sample .…”

“…The addition of nanoparticles (NPs) to surfactant-based foams has been proposed to enhance foam stability by generating small and uniformly trapped gas bubbles surrounded by thick lamellae films. − Synergetic interactions between surfactants and silica NPs and their impact on foam stability were studied in the presence and absence of oil using a layered heterogeneous porous medium with a permeability contrast of 1:6 . Silica-stabilized foam managed to divert injected fluids to low-permeability streaks, resulting in an incremental oil recovery of 34% over waterflooding .…”

“…The accumulation of EC within the foam lamellae induced a high-pressure drop across the fracture and diverted more gas into the matrix, resulting in improved oil recovery . In another study, a remarkable increase in the mobility reduction factor (MRF) was observed during core flooding experiments with MWCNT-based foam with no formation damage, compared to silica-based foam . This performance was attributed to the rod-like structure and partial hydrophobicity of the carbonaceous NPs …”

“…27 In another study, a remarkable increase in the mobility reduction factor (MRF) was observed during core flooding experiments with MWCNT-based foam with no formation damage, compared to silica-based foam. 48 This performance was attributed to the rod-like structure and partial hydrophobicity of the carbonaceous NPs. 48 Table 1 summarizes some of the recent studies on foam generation and foam EOR using different types of NPs in various media.…”

Graphene Quantum Dot-Stabilized Foam for Enhanced Oil Recovery

“…Using NPs in synergy with surfactants increased the strength of the generated foam and decreased the amount of surfactant used. , Gas bubbles in nanofluid-based foam were smaller, more uniform, and more stable against coalescence and coarsening compared to those in surfactant-based foam . Carbonaceous NPs have also been utilized as foam stabilizers. − Improved conformance control was particularly achieved with carbon nanodots, graphene oxide, and multiwalled carbon nanotubes. The superiority of NPs over surfactants in foam stabilization arises from various factors.…”