Enhanced Oil Recovery (EOR)
Crude oil has remained the major source of world energy supply despite considerable efforts on other sources of energy. On average, one-third of conventional reservoirs can be recovered through primary and secondary (i.e. waterflooding) oil recovery processes. The remaining oil-in-place is the target for enhanced oil recovery (EOR). Several EOR methods have been developed to recover bypassed and residual oil in the reservoir. These are majorly categorized into thermal and non-thermal EOR methods. Thermal EOR are unsuitable for reservoirs with great depth or thin pay zones. Hence, non-thermal EOR methods such as gas flooding, chemical flooding and microbial methods have received important attention over the last decades for oil recovery processes.
Nanotechnology for enhanced oil recovery (EOR), has been adjudged as an efficient oil recovery technique to recover bypassed oil and residual oil trapped in the reservoir. This EOR method relies on the injection of chemicals to boost oil recovery. Recently, due to the limitations of the application of chemical EOR methods to reservoirs having elevated temperatures and high salinity and hardness concentrations, nanotechnology have been applied to enhance its efficiency and improve oil productivity. The synergistic combination of nanoparticles and conventional EOR chemicals has opened new routes for the synthesis and application of novel materials with sterling and fascinating properties.
Nanotechnology is the application of nanoparticles characterized by a size ranging from 1 to 100 nm. In the oil and gas industry, applications of nanotechnology ranges from drilling processes, flow assurance, hydraulic fracturing, cementing, to EOR . For EOR process, the engineered nanomaterials are mixed with fluids that are injected into the reservoir to boost oil production.
The recent advances in these solutions, make the application of nanotechnology in the chemical EOR processes, a prime candidate to boost oil production. The mechanisms of oil recovery through nanotechnology are many and numerous strategies exist to apply this technology. Results of various nano experiments shows that the incorporation of nanotechnology with chemical EOR shows good potential to improve pore scale mechanisms. Furthermore, nanotechnology improved the rheological properties of polymer and stability of emulsions and foams indicating the good potentials of improving sweep efficiency of injected chemicals especially in the presence of harsh reservoir conditions. Finally, applications of nanotechnology, should focus on modeling the flow behavior of nanomaterials through porous media, which is required for the designing and field implementation of nano-chemicals EOR.
Current oil recovery methods with existing technologies are not satisfactory, and, depending on reservoir characteristics, an average of 50% of crude is left behind. Several enhanced oil recovery (EOR) methods have been investigated and proposed for field-scale implementations. The most widely studied EOR methods are based on surfactants, polymers, alkalis and their combinations as injection fluids.
EOR surfactants work on the principle of reducing interfacial tension (IFT) between crude oil and water, which helps to increase the capillary number and reduce residual oil saturation. Similarly, polymers also amplify the capillary number by increasing the viscosity of the injected fluid, which ultimately improves sweep efficiency.
However, conventional methods are not entirely adequate, due to poor recovery efficiency and the high cost of chemical injection, due primarily to shear degradation and excessive adsorption on rock matrix. Hence, a more efficient and economic EOR method is required.
Nano Particles to the Rescue
Oil Caption shows oil-wet petroleum reservoir after sweater injection – much of the oil remains trapped in the reservoir
OIL-wet petroleum reservoir after nanofluid injection. The nano particles employ different mechanisms to produce the remaining oils
Close-up of nano particles forming a wedge –like film to strip oil off the rock surface in oil-wet petroleum reservoir .
Water-wet petroleum reservoir after water flooding, where water is just flowing through the main channels
EOR with Nano Fluids
Intense interest has been shown in the development of “smart nanofluids” because they can dramatically change their flow properties in complex fluid systems.
IPX supplies smart nanofluid systems, in which associative silica nanoparticles (ASNPs) were incorporated to regulate their flow properties in rock pores.
The essence of our approach is to create long-range hydrophobic attraction between rock properties. This leads to the favorable formation of a wedge film as a result of structural disjoining pressure. This wedge film made the oil adsorbed on the rock surface more dewettable, thus, making the trapped oil, separate and flow, thus enhancing the efficiency of oil recovery.
Classifications of EOR
Wedge Film between Rock Interfaces
The NANOTECH Alternative for Enhanced Oil Recovery
Nanoparticle (NP)-based EOR (nano-EOR) is an alternative strategy. Nanoparticles, due to their relatively small size, large surface area and high surface charge density, have the potential to increase recovery efficiency at lower concentrations than conventional chemicals. Researchers globally have been studying various nanoparticles to assess their potential in EOR. Sustained efforts in the last several years have resulted in the discovery of several novel EOR mechanisms for nano-EOR such as: disjoining pressure log-jamming, wettability alteration, reduction of interfacial tension (IFT), viscosity enhancement and crude oil viscosity reduction.
Unlike surfactants and polymers, it is evident that there is no single, universally accepted mechanism for nanoparticles-enabled EOR. Although many mechanisms of nano-EOR have been proposed, a lack of direct connections between the pore-scale mechanisms and the macro-scale oil recovery performance makes it hard to determine which mechanisms are dominant. Nanoparticles are also increasingly studied for addressing key challenges to supplement conventional EOR methods by reducing surfactants adsorption, increasing polymer viscosity and reduce shear degradation. Therefore, it is important that a mechanism for nanoparticle-enabled recovery be identified, and pore-scale physics be validated and expanded in the pore-networks on a micro-model, then performance-validated in the reservoir core.
Nanoparticles – Smart Fluid- to Enhance Oil Recovery
Nanoparticles are having great attention as emerging technologies to be employed in the oil & gas field. These materials, indeed, could be used as sensors to be injected into the wells to understand the property of reservoir (pH, hydrocarbon saturation etc.) or as “smart-fluid” for increasing oil recovery altering wettability (more water-wet), improving mobility ratio and reducing interfacial tension. “Smart fluid” can be divided into three groups:
- metal oxide (Al2O3, CuO, Fe2O3/Fe3O4
- organic (i.e. carbon nanotubes)
- inorganic (i.e. silica)
Among the most promising results are seen by which using nanoparticles that are represented by carbon nanotubes(CNT). These compounds fall in fullerene category, have good resistance to corrosion. They can be arranged in single or multiple wall made of graphene and the surface is hydrophobic with high slip length. For other applications of nanoparticles in oil and gas industry such as corrosion inhibition, methane release from gas hydrate, etc. see diagram at right.
Taking Drilled Well – using Co2 Flood with Nanoparticles for increased production from the application of nanoparticles
Includes chemical flooding, thermal steam injection, miscible flooding, methods. These change the property of fluids to improve sweep efficiency by reducing the mobility ratio between injected and in-place fluids, eliminate or reduce the capillary and interfacial forces and thus improve displacement efficiency.