US 12,436,103 B2
Attenuated total reflection based measurement of refractive index and carbon dioxide concentration
Terizhandur S. Ramakrishnan, Boxborough, MA (US); and Robert O'Leary, Cambridge, MA (US)
Assigned to Schlumberger Technology Corporation, Sugar Land, TX (US)
Filed by Schlumberger Technology Corporation, Sugar Land, TX (US)
Filed on Mar. 3, 2023, as Appl. No. 18/178,085.
Claims priority of provisional application 63/269,882, filed on Mar. 24, 2022.
Prior Publication US 2023/0304928 A1, Sep. 28, 2023
Int. Cl. G01N 21/41 (2006.01); E21B 49/08 (2006.01); G01N 33/28 (2006.01)
CPC G01N 21/41 (2013.01) [E21B 49/081 (2013.01); G01N 33/2823 (2013.01); G01N 33/2841 (2013.01); G01N 2201/0638 (2013.01)] 20 Claims
OG exemplary drawing
 
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 comprise a first crystal and a second crystal, wherein the crystals have at least one of different refractive indices or different angles of incidence with respect to light directed to the crystals;
at least one light source coupled to the crystals and configured to direct the 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;
determine a crystal correction coefficient based on:
a first ratio of a first refractive index of the first crystal to a reference refractive index at the at least one wavelength; and
a second ratio of a second refractive index of the second crystal to the reference refractive index at the at least one wavelength, wherein the reference refractive index is between a third refractive index of diamond and a fourth refractive index of sapphire at the at least one wavelength;
normalize the attenuations based at least in part on the crystal correction coefficient; and
determine the refractive index of the formation fluid and a carbon dioxide concentration in the formation fluid utilizing the normalized attenuations to account for variations in the refractive index of the formation fluid.