Nanofiber spectral analysis

Abstract

Apparatus, systems, and methods may operate to transmit energy to a nanofiber sampling coil and / or a nanofiber reference coil. Further activity may include receiving the energy as modified by evanescent interaction with a sampled material located proximate to the sampling coil and / or as modified by propagation through the reference coil, and comparing the energy modified by evanescent interaction with the energy modified by propagation through the reference coil to determine a spectroscopic property of the sampled material. Additional apparatus, systems, and methods, including the use of nanofibers and fluorescence induced by evanescent radiation to conduct spectroscopic analysis, are disclosed.

Description

BACKGROUND [0001]Spectroscopic analysis in a downhole environment sometimes makes use of a window or window surface total internal reflection to examine various sample materials. Both configurations may use instrumentation of substantial size, since the light sources used tend to be of low intensity, leading to the use of optics that concentrate light source output for greater resolution.[0002]Windows have disadvantages when used in high-pressure environments, such as the difficulty of configuring the window mounting aperture to be pressure-tight, and keeping the window surface clean in the face of particle accumulation. Scattering via particles can greatly reduce the transmitted signal.[0003]To reduce the overall size of the apparatus involved, windowed configurations may be designed to trade a reduced path length for reduced sensitivity. When total internal reflection is used, path lengths may be even more limited. For example, the sampling depth in a given material may be limited...

AI Technical Summary

Problems solved by technology

Windows have disadvantages when used in high-pressure environments, such as the difficulty of configuring the window mounting aperture to be pressure-tight, and keeping the window surface clean in the face of particle accumulation.

When total internal reflection is used, path lengths may be even more limited.

While these difficulties with performing spectroscopic analysis may be compounded when attempted in a downhole environment, it should be noted that many of these problems are not unique to the petroleum recovery industry.

This leads to detection limits on the order of one part in 107 absorbance units.

This can result in diluting the intensity of a cleaning light pulse because the power of the pulse is distributed among more frequencies.

However, many macroscopic properties of oils are also matrix dependent.

One of the difficulties encountered in pressure feed-through systems for optical fibers (e.g., low pressure to high pressure) occurs when an epoxy is used to seal the fiber against the wall of the chamber.

Although the surface area of the fiber fed through the wall is sufficiently small that force on the fiber and epoxy is small, and high pressure sealing (beyond 400 MPa) is achievable, when the system heats or cools, the thermal expansion differential between the wall and fiber can break the fiber.

Images