The main objective of the INTER project is to develop Intelligent Environmental Reporters- green nanoparticles that can be used to measure residual oil directly in an environmentally friendly manner.
To understand how the particles can be used to estimate how much residual oil there is, and where, we will perform computer simulations in concert with physical experiments in the laboratory. We will also develop new analytical techniques that can read the particles' "memories", the oil reporters must be able to memorize how much oil they have encountered in the oil reservoir.
With time, all oil fields will experience a decline in production. To counteract this development, one may inject water into some wells and push the remaining oil towards other wells where it can be produced. Even after this, there is normally a lot of residual oil left. To determine how much, different methodes are used. One method is partitioning interwell tracer test (PITT), another is single well chemical tracer test (SWCTT). Both use the difference in flow speed of two different tracers. One tracer is a water tracer and the other is a partitioning tracer. Both are added to the injection water, and by measuring the difference in arrival time, an estimate of the residual oil can be given. This is important to know to plan continued oil production in a field. Unfortunately, today's tracer technology raises several health, safety and the environment (HSE) issues. Large volumes of highly flammable fluids may have to be stored on platforms or environmentally "red" chemicals are used.
The main objective of the INTER project is to develop Intelligent Environmental Reporters- green nanoparticles that can be used to measure residual oil directly in an environmentally friendly manner. To understand how the particles can be used to estimate how much residual oil there is, and where, we will perform computer simulations in concert with physical experiments in the laboratory. We will also develop new analytical techniques that can read the particles' "memories", the oil reporters must be able to memorize how much oil they have encountered in the oil reservoir.
So far in the project we have started the synthesis of carbon-silica hybrid nano particles, and silica particles doped with europium. These particles have further had their surface modified with a polymer. Preliminary results were presented at a conference in «Nanohybrides 16 Porquerolle June 2019» Measurement of particle stability in formation water has been started. Particles of silica with molybdate or tungstanate has also been synthesized. Molybdate and tungstanate will give increased fluorescence of europium, and thereby better sensitivity. These particles will be surface modified with polymers. Different oil soluble tracers will then be adsorbed to the polymer surface. The tracers will preferably be fluorescent dyes.
Numerical models for the aggregation of nanoparticles have been developed, and these models will be important for the quantitative interpretation of the flow experiments. The work on safer by designs has also started. Tests have been made with passive tracers like sodium iodide and known silica nanoparticles. Furthermore, XDLVO modeling with Comsol Multiphysics has been carried out considering how nanoparticles with different properties behave under varying conditions - rock, formation water, temperature, etc. The simulations consider van der Waals forces, EDL and Born repulsion as well as the velocity and Brownian motion.
Lyon has performed some tests of the first nanoparticles from NTNU. Several aspects have been revealed:
- we measured the hydrodynamic size under the two solvents and check the stability at room temperature
- we performed the excitation, emission and lifetime decay rates for both solutions and solid sample.
- the correlation curves collected by dynamic light scattering reveals aggregation of samples around 2 micrometers that decreases progressively after 12 hours to reach an average value of 500 nm.
After redispersion by sonication the particles remain on these levels independently of solvent used (a check with an intermediate polarity using isopropanol was performed)
The fluorescent spectra reveal a slight intense signal in the UV-visible zone in the range 400-500 nm with some narrow peaks that are common of powder and solution and no phosphorescence signal in the ms range. The lifetime value is estimated around 7 microseconds under excitation 340 and emission 440 nm.
A batch of nano-sized silica particles made in the INTER project have been tested for their potential to damage the DNA and induce carcinogenic effects. The effect on DNA was tested on a human lung cell line, and on liver- and gill cell lines from Rainbow trout.
The particles did not induce a significant effect on the DNA, indicating a low genotoxic potential. Non-genotoxic substances may, however be carcinogenic. This can be tested with use of the so-called cell transformation assay, in which carcinogenic substances induce morphological changes in the appearance cells. Based on two separate experiments, there are indications that the silica nanoparticles can induce cell transformation at relatively high concentrations (> 10 µg/cm2), indicating a carcinogenic potential. Further experiments will be performed to confirm this observation, but the observation emphasize the importance of testing manufactured nanoparticles for their potential toxicity to do a proper risk assessment.