Nanomaterials for Oil and Gas Exploration and Production
Reliable methods for mapping and controlling the flow of fluids in the subsurface are central to extracting hydrocarbons. If water or gas is injected to enhance the recovery of oil, it is important that the front of the injected fluid move as uniformly as possible through the rock formation so that the oil is completely swept to the recovery wells. Fingering of the injected fluid short circuits the sweep and bypasses valuable oil.
Lawrence M. Cathles, Professor in Earth and Atmospheric Sciences
KAUST-CU investigates NIMs and their covalent analogs nanoparticle organic hybrid materials (NOHMs) as non-diffusing tracers and interfacial agents for oil and gas exploration and production.
- Nanoparticle Tracers and Sensors
Nanoparticles that do not stick to the rock surface or hydrocarbon phases act as tracers that move much more quickly through the rock formation than conventional chemical tracers. The reason for this is that the relatively large nanoparticles do not diffuse from the channels of fluid flow into the adjacent rock as do chemical tracers. A nanoparticle tracers can therefore reveal how a seep fluid leaving one part of a well short-circuits to a recovery well after only perhaps a week rather than months of injection. Furthermore, comparing the arrival of chemical and nanoparticle tracers can show how channeled the flow is, and this can be important to remediation. Since nanoparticles can be tagged with bar codes of different fluorescent color, a great many tracer experiments could be run simultaneously in a reservoir, providing a great deal of information about fluids movement. We are running laboratory sand pack experiments to demonstrate that nanoparticles can measure fluid bypass, and at the same time we are developing field-capable methods for reading fluorescent and other nanoparticles. Our ultimate goal is to show how nanoparticle tracers can image fluid flow in a hydrocarbon reservoir during secondary recovery operation. - Nanoparticle Rheology Modifiers
Once the entry points of fluid bypass in an injection well have been identified, the issue becomes how to plug or reduce the bypass. During hyrdro-fracturing questions regarding the uniformity of fluid flow also arise. Nanoparticles can modify fluid rheology under both high and low Reynolds number (Re) conditions. We are investigating how they achieve these changes through a combination of theoretical analysis and experiment. High Re conditions are applicable to hydro-fracturing and perhaps wellbore skin effects. Low Re conditions apply to the management of bypass.
In the fracing and near-well applications flow can be strongly sheared and dilatent, and the critical issues are the shear-thinning character and possible thixotropy of the fluids. What is needed is a clear understanding the flow of NIMs/NOHMs dispersions under high Re number condition. Flow past objects and understanding the effects of extensional flow on the viscoelastic properties are crucial. Work in this area combines (i) fundamental molecular modeling with (ii) fluid mechanics simulations / theory, (iii) rheological and micro-fluidic studies, and (iv) in-situ structural studies using microscopy and scattering. These fundamental studies can then be assessed in the sand-pack experiments and also in single and multi-phase flows core experiments.
For mobility and profile control applications we seek to understand the chemical structure and the assembly of molecular and nanoparticles of the NIMs and NOHMs and how this affects the shear dependence of their viscoelastic properties and the behavior of aqueous and oil dispersions. The critical question is whether the addition of small quantities of NIMs/NOHMs to reservoir brine could allow reservoir profile modification over protracted periods of time under high temperature, high pressure, high salinity reservoir conditions. Molecular models of the short and long-range particle interactions in dilute solutions that we are constructing may provide useful insight. In the longer term we will focus on the viscoelastic changes that might be triggered as the nanoparticles move from an aqueous to oil phase environment or into a different rock or pore fluid environment. - Nanoparticles as Surfactants and Interfacial Modifiers
NIMs/NOHMs modify the surfactant / interfacial properties of the oil-water-gas system and this could provide a basis for Enhanced Oil recovery applications. Through model studies, contact angle measurements, and interfacial rheometry on well characterized NIMs and NOHMs we are investigating how the structure and chemistry of the NIMs/NOHMs allows them to modify interfacial properties by lowering interfacial tension or by changing the wettability of the rock. The these changes will then be tested in displacement core studies and assessed in terms of the impact they could have on the capillary seals that impede oil recovery.
