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.

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 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 118 nm. The foam system was optimized for its maximum half-life by varying the concentration of the AOS and the nanotube from 0.2-1% and 250-1,000 ppm, respectively. Compatibility testing with salts were done as well. Coreflood experiments with 1.5 in. diameter and 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% 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 70% greater nitrogen foam half-life (32 minutes) than an optimized AOS-silica system at 150°F. The foam half-life of a standalone 0.5% AOS solution was 7 minutes. In 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 standalone 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.

Water production post hydraulic fracturing is an issue that has been facing E&P operators worldwide for a long time. The water quantities produced can be significant with great amount of impurities. This not only reduces the oil production in those wells, but can also cause problems such as sand production, scale, corrosion and erosion. Moreover, it costs the E&P operators a lot of money every year to treat and dispose these produced waters. Crosslinked gels have been used successfully in the oil and gas industry to shut-off water producing zones. This study presents an experimental investigation of a polyacrylamide-based polymer and polyethyleneimine (PEI) system for water shut-off treatments. The polyacrylamide-based polymer has a molecular weight of 40,000 Daltons. PEI crosslinker was obtained in a 50:50 aqueous solution with a molecular weight of 60,000 Daltons. The HP/HT rheometer was used to conduct the viscosity measurements. All experiments were done at a pressure of 400 psi. The shear rate was fixed at 100 s−1 and the temperature was ranged from room temperature to 350℉. The gelation time and the system's viscosity were both studied as a function of polymer concentration and salt concentration in the mixing water. Additionally, the effect of increasing temperature on the gelation time was examined. Moreover, an HP/HT aging cell was used to generate the gel that was used later for compatibility testing with a treated formation water from the Wolfcamp. Increasing the polymer concentration was found to decrease the gelation time and increase the system's viscosity up to a specific limit. Moreover, we observed an increase in the gelation time as the concentration of NaCl was raised in the mixing water, however the system's viscosity decreased. Also, we noticed a decrease in the gelation time as the temperature increased. Finally, no incompatibility issues were observed between the polyacrylamide-based polymer/PEI system and the treated formation water. Polymer-crosslinker systems should be stable and highly viscous to ensure an effective water shut-off operation. This work experimentally investigates the performance of a cheap polyacrylamide-based polymer and PEI organic gel system. The paper shows that the tested system is capable of sealing water production zones and can provide a promising alternative to current water shut-off systems used in the field.