Precise manipulation and control of matter at dimensions of 1–100 nm have transformed many industries including the oil and gas industry. Nanosensors enhance the resolution of subsurface imaging, leading to advanced field-characterization techniques. Nanotechnology could greatly enhance oil recovery by use of molecular modification and by manipulating interfacial characteristics. Egypt’s oil consumption has grown by more than 30% in the past 10 years. Hydrocarbon reserves in Egypt have increased 5%/year over the past 7 years, while the average recovery factor remains at 35%. Nanotechnology is key to solving this production/consumption imbalance.
Introduction
Nanotechnology is the use of very small pieces of material, with dimensions between approximately 1 and 100 nm, by themselves or by manipulation to create new larger-scale materials with unique phenomena enabling novel applications. A nanometer is one-billionth of a meter—a distance equal to two to twenty atoms laid down next to each other (depending on the type of atom).
Nanotechnology refers to manipulating the structure of matter on a length scale of nanometers, interpreted at different times as meaning anything from 0.1 nm (controlling the arrangement of individual atoms) to 100 nm or more. Fig. 1 compares the scale of various items referenced to a nanometer.
Engineered Nanomaterials
Nanoparticles are the simplest form of structures with sizes in the nanometer range. In principle, any collection of atoms bonded together with a structural radius <100 nm can be considered a nanoparticle. The tiny nature of nanoparticles yields useful characteristics, such as increased surface area to which other materials can bond in ways that make stronger or lighter materials. At the nanoscale, size is a factor regarding how molecules react to and bond with each other.
Suspensions of nanoparticles are possible because the interaction of the particle surface with the solvent is strong enough to overcome differences in density, which usually would result in a material either sinking or floating in a liquid-forming nanofluid. Nanofluids for oil and gas applications are defined as any fluid used in the exploration and exploitation of oil and gas that contains at least one additive with a particle size in the range of 1–100 nm. A few oilfield uses are described in the following. See the complete paper for additional uses and details.
Exploration
Nanoparticles with noticeable alterations in optical, magnetic, and electrical properties compared with their bulk counterparts are excellent tools for developing sensors and imaging-contrast agents. Hyperpolarized-silicon nanoparticles provide a tool for measuring and imaging in oil exploration.
There are several programs to develop nanosensors with temperature and pressure ratings allowing use in deep wells and hostile environments. Nanosensors are deployed into the pore space by means of nanodust to acquire data on reservoir characterization, fluid-flow monitoring, and fluid-type recognition. Nanocomputerized tomography can image tight gas sands, tight shales, and tight carbonates in which the pore structure is too small to be detected with conventional computerized-tomography techniques.
Fluid-Loss Control and Wellbore Stability. Several researchers are investigating the use of nanoparticles as drilling-fluid additives to reduce fluid loss and enhance wellbore stability. Filter cake developed with nanoparticle-based -drilling-fluid filtration is very thin, which implies high potential for reducing differential-pressure sticking and formation damage while drilling.
In shale formations with nanodarcy permeability, the nanometer-sized pores prevent the filter cake from forming, which in turn allows fluid loss. Nanoparticles can be added to the drilling fluid to minimize shale permeability by physically plugging the nanometer-sized pores and shutting off water loss. Hence, nanoparticles can provide a solution in environmentally sensitive areas where oil-based muds currently are used for shale-instability problems.
Torque and Drag. Because nanomaterials can form fine and very thin films, nanoparticle-based fluids can significantly reduce the frictional resistance between the pipe and the borehole wall by forming a continuous thin lubricating film at the wall/pipe interface. Also, the tiny spherical nanoparticles may create an ultrathin ball-bearing-type surface between the pipe and the borehole wall that would allow easy sliding of the drillstring along the nanoparticle-based ball-bearing-type surface. Nanoparticle-based fluids could be especially useful in reducing the torque-and-drag problems in horizontal, extended-reach, multilateral, and coiled-tubing drilling.
High-Pressure/High-Temperature (HP/HT) Challenges. In HP/HT drilling operations, many drilling-fluid systems have a relatively poor heat-transfer coefficient. The cooling efficiency of traditional drilling fluids decreases because of slow heat dissipation from the surfaces of downhole tools and equipment. Hence, there is a higher probability of equipment failure caused by thermal degradation. The extremely high surface-area/volume ratio of nanoparticles enhances the thermal conductivity of nanoparticle-based drilling fluids, providing efficient cooling of the drill bit and leading to a significant increase in the operating life cycle of a drill bit.
Diamond-Nanoparticle Technology. Carbon nanomaterials have unique combinations of mechanical, structural, electrical, and thermal properties. Diamond nanoparticles have been functionalized for polycrystalline-diamond applications such as polycrystalline-diamond-compact (PDC) cutters for drill bits. Diamond nanoparticles provide unique surface characteristics to PDC cutters that allow them to integrate homogeneously into the PDC synthesis.
High-Strength Nanostructured Materials. Flow-control and completion devices (e.g., fracturing balls, disks, and plugs) are used for sleeve actuation or stimulation diversion during fracturing. Traditional lightweight material for ball or plug applications is prone to early deformation. The yield strength of conventional aluminum alloys usually is less than 400 MPa. Nanotechnology can be used to enhance the mechanical properties (and other properties) through engineering the material microstructure. Controlled-electrolytic-metallic nanostructured materials are lighter than aluminum and stronger than some mild steels, but disintegrate when exposed to the appropriate fluid. The disintegration process works through electrochemical reactions that are controlled by nanoscale coatings that are part of the composite-grain structure. The nanomatrix of the material is high strength and has unique chemical properties that are not available in conventional materials.
Cement Properties. Because of the very high surface area of nanomaterials, they can be used in casing cementing to accelerate the cement-hydration process, increase the compressive strength, help control fluid loss, reduce the probability of casing collapse, and prevent gas migration, a common cementing problem in gas wells. Also, the required quantity of nanomaterials is small.
Production
Gas hydrate is an ice-like crystalline solid formed from a mixture of water and natural gas, usually methane. Hydrates can produce a gaseous-methane volume 160 times the hydrate volume. Injecting air-suspended self-heating Ni-Fe nanoparticles (50 nm) into the hydrate formation through a horizontal well has been suggested. These particles will penetrate deep into the Class I, II, and H hydrate reservoirs by passing through the cavities (86- to 95-nm diameter). Self-heating of Ni-Fe particles in a magnetic field is caused by hysteresis loss and relaxation losses. These particles provide a temperature rise up to 42°C in the formation, disturbing the thermodynamic equilibrium and causing the water cage to decompose and release methane. In this technique, the pressure of the fluids in contact with hydrate is lowered, pushing the hydrate out of its stability region, which results in its decomposition.
Viscoelastic-Surfactant (VES) Stimulation. High-molecular-weight crosslinked-polymer fluids have been used to stimulate oil and gas wells for decades. These fluids exhibit exceptional viscosity, thermal stability, proppant transportability, and fluid-leakoff control. However, a major drawback of crosslinked-polymer fluids is the amount of polymer left behind. Polymer residue can damage formation permeability and reduce fracture conductivity significantly.
Nanoparticles, through chemisorption and surface-charge attraction, associate with VES micelles to stabilize fluid viscosity at high temperatures and produce a pseudofilter cake of VES fluid that reduces fluid loss significantly. When internal breakers are used to break the VES micelles, the fluid viscosity will decrease dramatically and the pseudofilter cake will break into nanometer-sized particles. Because the particles are small enough to pass through the pore throats of producing formations, they will flow back with the producing fluids and no damage will be generated.
Reservoir Characterization and Management
Nanoparticles are small enough to pass through pore throats in typical reservoirs, but they can be retained by the rock. Nanoparticles in an aqueous dispersion will assemble into structural arrays at a discontinuous phase such as oil, gas, paraffin, or polymer. The nanoparticles in this three-phase-contact region tend to form a wedge-like structure and force themselves between the discontinuous phase and the substrate. Particles in the bulk fluid exert pressure forcing the nanoparticles in the confined region forward, imparting the disjoining-pressure force. The energies that drive this mechanism are Brownian motion and electrostatic repulsion between the nanoparticles.
The force imparted by a single nanoparticle is extremely weak, but when a large amount of nanoparticles exists, referred to as the particle-volume fraction, the force can be upward of 50 kPa at the vertex, as shown in Fig. 2. When this force is confined to the vertex of the discontinuous phase, displacement occurs in an attempt to regain equilibrium.
Challenges in Egypt
Egypt’s domestic demand for oil is increasing rapidly. Local production has not kept up with this demand increase. Field development is considered an effective solution to meet the increasing energy demand. Nanotechnology could be key to solving this production challenge because it helps increase oil recovery while decreasing the cost of production by eliminating problems that occur throughout field operations.
To increase production, Egypt has a large heavy-oil resource to develop. Also, unconventional resources have not been explored. Current technology updates must be applied to explore more fields and improve development operations.
Advanced exploration methods, remote sensing, and improved-resolution seismic are needed. Nanosensors for imaging can improve exploration success by improving data gathering, recognizing shallow hazards, and avoiding dry holes. To decrease production costs, many solutions have been mentioned for the largest problems in development operations including drilling, cementing, logging, completion, and production.
The use of silica nanoparticles on an Egyptian formation was studied to compare waterflooding and nanofluid flooding. Fig. 3 above shows that waterflooding displaced the oil to recover 36% of the original oil in place (OOIP) at the breakthrough point. Nanofluid flooding recovered 67% of OOIP at the breakthrough point. This increase shows that the nanofluid can displace oil better than the water can.
Conclusions
Potential applications of nanotechnology include the following:
- Improvement of exploration by improving data gathering, recognizing shallow hazards, and avoiding dry holes
- Providing strength and endurance through nanotechnology-enhanced materials to increase the performance and reliability in drilling, tubular goods, and rotating parts
- Improvement of elastomers that are critical to deep drilling and drilling in HP/HT environments
- Production assurance through diagnostics, monitoring/surveillance, and management strategies
- Selective filtration and waste management for water
- Enhanced oil and gas recovery through reservoir-property modification, facility retrofitting, gas-property modification, and water injection.
This article, written by Dennis Denney, contains highlights of paper SPE 164716, “Applications of Nanotechnology in the Oil and Gas Industry: Latest Trends Worldwide and Future Challenges in Egypt,” by Abdelrahman Ibrahim El-Diasty, SPE, and Adel M. Salem Ragab, American University in Cairo and Suez University, prepared for the 2013 North Africa Technical Conference & Exhibition, Cairo, 15–17 April. The paper has not been peer reviewed.