DE-FE0005979

Goal
The goal of this project is to develop and evaluate, through coreflood tests at reservoir conditions, a nanoparticle-stabilized carbon dioxide (CO₂) foam system that can improve CO₂ sweep efficiency in CO₂ enhanced oil recovery (EOR) and minimize particle retention in the reservoir.

Performer
New Mexico Institute of Mining and Technology/Petroleum Recovery Research Center, Socorro, NM 87801-4681

Background
Improving oil production is becoming more crucial as worldwide oil demand rapidly increases, and the development of new technology is needed to fulfill this demand. In particular, EOR with CO₂ is regarded as a promising technology to not only improve oil production, but also to mitigate carbon emissions through their capture and storage in deep geologic formations. A revised national resource assessment for CO₂-EOR (July 2011) prepared for DOE by Advanced Resources International indicated that “Next Generation” CO₂-EOR can provide 137 billion barrels of additional technically recoverable domestic oil, with about half (67 billion barrels) economically recoverable at an oil price of $85 per barrel. However, CO₂ flooding processes frequently experience poor sweep efficiency despite the favorable characteristics CO₂ has for achieving dynamic miscibility with oil under most reservoir conditions. Because the mobility of CO₂ is high compared to that of oil, channeling that initially results from reservoir heterogeneity can be further increased, thus strengthening the need for mobility control during CO₂ flooding.

Research results have demonstrated that surfactant-induced CO₂ foam is an effective method for mobility control in CO₂ foam flooding. However, surfactant-stabilized CO₂ foams have some potential weaknesses. Because the foam is by nature ultimately unstable, its long-term stability during a field application is difficult to maintain. This is especially true when the foam contacts the resident oil. Under high-temperature reservoir conditions surfactants generally tend to degrade before they fulfill their long-term function. In addition, surfactant loss in a reservoir due to adsorption in porous media results in a large consumption of chemicals and is a major factor governing the economic viability of CO₂ foam flooding.

New nano-science technologies may provide an alternative for the generation of stable CO₂ foam. It is known that small solid particles can adsorb at fluid/fluid interfaces to stabilize drops in emulsions and bubbles in foams. The solid-stabilized dispersions may stay stable for years upon storage. The use of nanoparticles instead of surfactant to stabilize CO₂ foam may overcome the long-term instability and surfactant adsorption loss issues that affect surfactant-based CO₂-EOR processes. The high adhesion energy of the particles enables adsorption and is essentially irreversible, thus solid nanoparticles strongly and preferentially adsorb to either the water or gas phase at the water/CO₂ interface and create a protective barrier around each dispersed bubble of gas (if the nanoparticle is hydrophilic) or drop of water (if the nanoparticle is hydrophobic) to produce highly stable and durable foam. These properties imply that long-term stabilization of nanoparticle-stabilized CO₂ foam may be obtained.

Impact
Successful results of the planned experiments, together with the development of the nanoparticle-stabilized CO₂ foam and an evaluation of its potential for field testing, will benefit the oil industry in its enhanced recovery efforts. Nanoparticles are solid and can withstand harsh environments and high temperatures; thus, a successful project will extend the benefits of CO₂ flooding to those high-temperature reservoirs in which surfactant-stabilized CO₂ foam cannot survive. A successful project will provide an alternative CO₂-EOR technology that may drastically reduce the costs of a CO₂-EOR operation and, in addition, provide promising economic benefits from further oil recovery.

Accomplishments
Silica nanoparticles easily passed through the sandstone core without changing its permeability. Little adsorption was observed as nanosilica particles flooded the limestone core and core permeability remained unchanged. Core plugging did occur and core permeability was changed with injection of nanoparticles into a dolomite core.

Very stable and uniform CO₂ foam was generated when CO₂ and nanosilica dispersion flowed through a sandstone core sample. Carbon dioxide foam could be generated at a nanosilica concentration as low as 500 ppm. Increasing nanosilica concentration reduced foam mobility and increased the foam resistance factor. Increasing foam quality from 20% to 60% decreased CO₂ foam mobility; however, an additional increase in foam quality from 60% to 80% increased CO₂ foam mobility. Carbon dioxide foam mobility decreased with an increase in total flow rate and increased with an increase in core permeability.

Research also demonstrated that the addition of a small amount (30–50 ppm) of surfactant to a nanoparticle solution significantly improved CO₂ foam generation and foam stability.

Nanoparticle-stabilized CO₂ foam was observed to improve the residual oil recovery in sandstone core. The residual oil saturation decreased from 39.2% (after water flooding) to 9.95% after 5 PV of nanosilica and CO₂ were injected.

Current Status (January 2013)
Current studies focus on nanosilica particle-stabilized CO₂ foam for residual oil recovery at various pressures (1200, 1800, and 2500 psi) and temperatures (25, 45, and 60°C). Limestone core samples are being flooded with brine to obtain a residual oil saturation. Then 5 PV nanosilica dispersion and CO₂ are injected into the core to improve residual oil recovery. Pressure drop across the core is monitored during the experiments and oil recovery attributable to CO₂ foam is estimated. Particle retention and CO₂ captured in the core sample are being measured and calculated. The effects of pressure and temperature on foam performance and residual oil recovery are being investigated.

Researchers will continue to investigate CO₂-nanoparticle foam flooding with dolomite and limestone cores to investigate interactions between nanoparticles and other rock types and determine residual oil recovery.

Project Start: October 1, 2010
Project End: January 31, 2014

DOE Contribution: $772,934
Performer Contribution: $385,888

Contact Information:
NETL – Sinisha (Jay) Jikich (sinisha.jikich@netl.doe.gov or 304-285-4320)
NMIMT/PRRC - Ning Liu (ningliu@prrc.nmt.edu or 575-835-5739)
If you are unable to reach the above personnel, please contact the content manager

Additional Information

CO2 EOR: Nanotechnology for Mobility Control Studied [PDF-1.65MB] - News Release July, 2012