Apparatus and methods for measuring the refractive index of a fluid

Patent metadata

Field	Value
Publication number	US-2019079007-A1
Application number	US-201715699177-A
Country	US
Kind code	A1
Filing date	Sep 8, 2017
Priority date	Sep 8, 2017
Publication date	Mar 14, 2019
Grant date	—

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 that receives the fluid; two unalike crystals having faces in contact with fluid in the fluid flow line, said crystals having at least one of different refractive indices and angles of incidence; at least one light source coupled to said two unalike crystals for directing light into said 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 crystals and the fluid; at least one light detector coupled to said two crystals for measuring the reflected light exiting said crystals; and a processor coupled to said at least one light detector, said processor determining attenuations of said light entering said crystals and determining said refractive index of the fluid utilizing said attenuations.

2 . The borehole apparatus of claim 1 , wherein said processor determines said refractive index utilizing said refractive indices and said angles of incidence of said crystals.

3 . The borehole apparatus of claim 2 , wherein said processor determines said refractive index according to

A
2

A
1

=

K
2



η

c



1

K
1



η

c



2



sin
2



Θ
1



(

η
f

/

η

c



1

)

2

sin
2



Θ
2



(

η
f

/

η

c



2

)

2

,

where A 1 and A 2 are said attenuations of a first and a second of said crystals, η f said refractive index of the fluid, η c1 is the refractive index of said first crystal, η f is the refractive index of the second crystal, Θ 1 is the angle of incidence of the first crystal, and Θ 2 is the angle of incidence of the second crystal.

4 . The borehole apparatus of claim 2 , wherein said processor determines said refractive index according to

A
1

A
2

=

K
1



d

p



1

K
2



d

p



2

=

h


(

η

c


Assignees

• Schlumberger Technology Corp

Inventors

• Sharma Richa
• Shankar Raji
• Ramakrishnan Terizhandur S

Classifications

• G01N21/41

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

• E21B49/081

  with down-hole means for trapping a fluid sample (E21B49/10 takes precedence) · CPC title

• G01N21/3577 Primary

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

• G01N21/552 Primary

  Attenuated total reflection · CPC title

• G01N2021/1755

  and using two apparatus or two probes · CPC title