Attenuated total reflection based measurement of refractive index and carbon dioxide concentration

Patent metadata

Field	Value
Publication number	US-2023304928-A1
Application number	US-202318178085-A
Country	US
Kind code	A1
Filing date	Mar 3, 2023
Priority date	Mar 24, 2022
Publication date	Sep 28, 2023
Grant date	—

Abstract

Systems and methods presented herein generally relate to a tool for determining a refractive index of a formation fluid using attenuated total reflection. The tool includes a body having a fluid admitting assembly and a flow line that receives the formation fluid. The tool also includes two different crystals having faces in contact with fluid in the flow line. The tool further includes at least one light source coupled to the crystals and configured to direct light into the crystals. In addition, the wavelength, the refractive indices, and the angles of incidence are configured such that the light undergoes total internal reflection at interfaces between the crystals and the formation fluid. The tool also includes at least one light detector coupled to the crystals and configured to measure reflected light exiting the crystals. The tool further includes at least one processor coupled to the at least one light detector.

First claim

1 . A tool for determining a refractive index of a formation fluid, comprising:
a body having a fluid admitting assembly and a flow line that receives the formation fluid; two different crystals having faces in contact with fluid in the flow line, wherein the crystals have at least one of different refractive indices and different angles of incidence; at least one light source coupled to the crystals and configured to direct light into the crystals, wherein the light has at least one wavelength, and wherein the wavelength, the refractive indices, and the angles of incidence are configured such that the light undergoes total internal reflection at interfaces between the crystals and the formation fluid; at least one light detector coupled to the crystals and configured to measure reflected light exiting the crystals; and at least one processor coupled to the at least one light detector, wherein the at least one processor is configured to continuously and iteratively, in substantially real-time:
determine attenuations of the light entering the crystals; and
determine the refractive index of the formation fluid and a carbon dioxide concentration in the formation fluid utilizing the attenuations to account for variations in the refractive index of the formation fluid.

2 . The tool of claim 1 , wherein the at least one processor is configured to determine the refractive index of the formation fluid utilizing the attenuations to account for variations in penetration depth.

3 . The tool of claim 1 , wherein the at least one processor is configured to determine the refractive index of the formation fluid at the temperature and pressure of the sampled fluid.

4 . The tool of claim 1 , wherein the at least one processor is configured to determine the refractive index of the formation fluid correcting for background radiation.

5 . The tool of claim 1 , wherein the at least one processor is configured to use a plurality of reference wavelengths to determine the refractive index of the formation fluid, wherein each reference wavelength of the plurality of reference wavelengths corresponds to a different attenuation coefficient of a component in the formation fluid.

6 . The tool of claim 1 , wherein the at least one processor is configured to normalize the gain with respect to a reference fluid.

7 . The tool of claim 1 , wherein the at least one processor is configured to estimate optimal concentrations of components in the formation fluid.

8 . The tool of claim 1 , wherein the at least one processor is configured to verify light and heavy component concentrations in the formation fluid.

9 . The tool of claim 1 , wherein the two different crystals comprise different materials.

10 . The tool of claim 1 , wherein each of the crystals comprises diamond, sapphire, or zirconia.

11 . A method for determining a refractive index of a formation fluid, comprising:
placing into a borehole a tool having a fluid admitting assembly, a flow line, two different crystals in contact with the formation fluid in the flow line, at least one light source, at least one light detector and associated signal processing circuitry, and at least one processor, wherein the crystals have at least one of different refractive indices and different angles of incidence; moving the fluid admitting assembly of the tool into contact with a formation at a location of interest in the formation; causing formation fluid to flow into the flow line of the tool and into contact with the crystals; directing light from the at least one light source into the crystals; detecting with the at least one light detector the light exiting the crystals, wherein the crystals and the at least one light source are configured such that the light will undergo total internal reflection at interfaces between the crystals and the formation fluid; using the associated signal processing circuitry to compare the exiting light to a reference light value for the at least one light source associated with the at least one detector in order to obtain attenuation values; and using the at least one processor to continuously and iteratively, in substantially real-time:
determine attenuations of the light entering the crystals;
determine the refractive index of the formation fluid; and
determine a carbon dioxide concentration in the formation fluid utilizing the attenuations to account for variations in the refractive index of the formation fluid at measurement wavelengths and reference wavelengths.

12 . The method of claim 11 , comprising using the at least one processor to determine the refractive index of the formation fluid utilizing the attenuations to account for variations in penetration depth.

13 . The method of claim 11 , comprising using the at least one processor to determine the refractive index of the formation fluid at the fluid conditions of temperature and pressure.

14 . The method of claim 11 , comprising using the at least one processor to determine the refractive index of the formation fluid correcting for background radiation.

15 . The method of claim 11 , comprising using the at least one processor to use a plurality of reference wavelengths to determine the refractive index of the formation fluid, wherein each reference wavelength of the plurality of reference wavelengths corresponds to a different attenuation coefficient of a component in the formation fluid.

16 . The method of claim 11 , comprising using the at least one processor to estimate optimal concentrations of components in the formation fluid.

17 . The method of claim 11 , comprising using the at least one processor to verify light and heavy component concentrations in the formation fluid.

18 . The method of claim 11 , wherein the two different crystals is composed of different materials.

19 . The method of claim 11 , wherein each of the crystals is composed of diamond, sapphire, or zirconia.

20 . A tool for determining a refractive index of a formation fluid, comprising:
two different crystals having faces in contact with fluid in a flow line, wherein the crystals have at least one of different refractive indices and different angles of incidence; at least one light source coupled to the crystals and configured to direct light into the crystals; at least one light detector coupled to the crystals and configured to measure reflected light exiting the crystals; and at least one processor coupled to the at least one light detector, wherein the at least one processor is configured to continuously and iteratively, in substantially real-time:
determine attenuations of the light entering the crystals; and
determine the refractive index of the formation fluid and a carbon dioxide concentration in the formation fluid utilizing the attenuations to account for variations in the refractive index of the formation fluid.

Assignees

• Schlumberger Technology Corp

Inventors

• Ramakrishnan Terizhandur S
• O'Leary Robert

Classifications

• G01N21/41 Primary

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

• G01N33/2823 Primary

  Raw oil, drilling fluid or polyphasic mixtures · CPC title

• G01N33/2841

  Gas in oils, e.g. hydrogen in insulating oils · CPC title

• E21B49/081

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

• G01N2201/0638

  Refractive parts · CPC title