Application of nanoparticles in downhole detection

The revolution of nanotechnology leads to the increasing application of nanoparticles in many industry fields. Nanoparticles, due to the small size, are supposed to transport through subsurface formation without breaking rock structure and thus have received tremendous attention1-12. Nanoparticles also have many unique physical, chemical and optical properties, which are not found in bulk samples with the same chemical composition. Such nanoparticles, therefore, may be attractive as candidates to detect the chemical and physical properties underground, by directly interact with the important targets. Because of the increasing energy demands, it becomes more desirable to develop new technology to detect the downhole conditions. In this paper, nanoparticles possessing functionalized carbon black cores and treated polyvinyl alcohol addends was designed as carrier to deliver probe molecules into the reservoir. When applied in the aqueous environment, nanoparticles tend to interact with the rock surface, which may affect the mobility and stability of the nanoparticles. Deposition of nanoparticles will remove the nanoparticles from the aqueous environment, and therefore understanding the fate and transport of nanoparticles is vitally important for determination of further application strategy. The stability and transport behavior were tested under high temperature, high salinity conditions through a variety of rock formations. A non-radioactive probe molecule, which can be easily detected by mass spectrometry, triphenolamine (TPA), was attached to the nanoparticles surface. When the nanoparticles passed through columns packing with different oil saturation ground rocks, the probe molecules, THA, was selectively released from nanoparticles. This study simulates detection and quantitative analysis of the hydrocarbon content in downhole rock formations, which is vitally needed for oilfield. This technology also shows the potential to be used for DNAPL detection in ground water remediation field. Crude oil is classified as “sour” when it contains total sulfur content greater than 0.5%. Among these sulfur species, H2S is the one of main impurities in sour crude. The sour crude is toxic and corrosive to the materials of construction in pipelines and other holding and transportation vessels. Since the sulfur amount in a sample of crude depends on where it was found, if the concentration of the sulfur species in the subsurface could be accurately monitored, then geologists might be able to evaluate the quality of the crude before large scale extraction ensues. A H2S-sensitive molecule was selected to be attached to nanoparticles surface and the detection ability of H2S concentration was tested. The experimental results show that the fluorescent enhancement of the H2S-sensitive addends correlates to the H2S content