Apparatus and methods for measuring the refractive index of a fluid

Patent metadata

Field	Value
Publication number	US-11085877-B2
Application number	US-201715699177-A
Country	US
Kind code	B2
Filing date	Sep 8, 2017
Priority date	Sep 8, 2017
Publication date	Aug 10, 2021
Grant date	Aug 10, 2021

Abstract

Methods and apparatus are provided for determining the refractive index of a downhole fluid. Two unalike crystals are provided having faces in contact with fluid in the fluid flow line of a borehole tool. The crystals are chosen to have different refractive indices and/or different angles of incidence, but to provide total internal reflection for light that is directed through the crystals to the crystal/fluid interface. The measured attenuations for each crystal are used in conjunction with the known refractive indices and angles of incidence of said crystals to determine the refractive index of the fluid.

First claim

What is claimed is:

1. A borehole apparatus for determining the refractive index of a fluid, comprising:
an elongate body having a fluid admitting assembly and a fluid flow line configured to receive the fluid;
a first crystal and a second crystal each having a face configured to be in contact with the fluid in the fluid flow line, wherein said first and second crystals have different refractive indices, different angles of incidence, or different refractive indices and different angles of incidence with respect to one another;
at least one light source coupled to said first and second crystals and configured to direct light into said first and second crystals, said light having at least one wavelength, and said wavelength, said refractive indices and said angles of incidence being chosen such that said light undergoes total internal reflection at interfaces between said first and second crystals and the fluid;
at least one light detector coupled to said first and second crystals configured to measure the reflected light exiting said crystals; and
a processor coupled to said at least one light detector, said processor configured to determine attenuations of said light entering said crystals and configured to determine said refractive index of the fluid utilizing said attenuations, said refractive indices, and said angles of incidence of said crystals, wherein said refractive index is determined according to:

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Assignees

• Schlumberger Technology Corp

Inventors

• Sharma Richa
• Shankar Raji
• Ramakrishnan Terizhandur S

Classifications

• G01N21/552 Primary

  Attenuated total reflection · CPC title

• G01N21/41

  Refractivity; Phase-affecting properties, e.g. optical path length (G01N21/21 takes precedence) · CPC title

• G01N2021/1751

  Constructive features therefore, e.g. using two measurement cells · CPC title

• G01N21/431 Primary

  Dip refractometers, e.g. using optical fibres · CPC title

• G01N21/3577

  for analysing liquids, e.g. polluted water · CPC title