Mid-infrared carbon dioxide sensor

Patent metadata

Field	Value
Publication number	US-2017242149-A1
Application number	US-201515511164-A
Country	US
Kind code	A1
Filing date	Sep 9, 2015
Priority date	Sep 15, 2014
Publication date	Aug 24, 2017
Grant date	—

Abstract

A sensor for monitoring CO 2 in a fluid regardless of the phase properties of the fluid, i.e., regardless of whether the fluid contacting the window is a liquid water-based phase, a liquid oil-based phase, a mixture of liquid water and liquid oil-based phases, or a gas phase. The sensor includes an internal reflection window for contacting with the fluid. A mid-infrared light source directs a beam of mid-infrared radiation into the window and the beam is internal reflected at an interface between the window and the fluid. The reflected beam is passed through three narrow bandpass filters which preferentially transmit mid-infrared radiation over bands of wavelengths corresponding to absorbance peaks of water, oil and CO 2 . The amount of CO 2 is determined from the intensities of the mid-infrared radiation passing through the three filters

First claim

1 . A sensor for monitoring CO 2 in a fluid, the sensor comprising:
an internal reflection window configured in use to contact the fluid; a mid-infrared light source configured to direct a beam of mid-infrared radiation into the window to provide for attenuated internal reflection of the beam of mid-infrared radiation at an interface between the window and the fluid; a set of three narrow bandpass filters configured to filter the internally reflected mid-infrared radiation received from the window wherein:
a first narrow bandpass filter of the set of three narrow bandpass filters comprises a water filter and is configured to preferentially transmit mid-infrared radiation over a band of wavelengths corresponding to respective absorbance peaks of water;
a second narrow bandpass filter of the set of three narrow bandpass filters comprises an oil filter and is configured to preferentially transmit mid-infrared radiation over a band of wavelengths corresponding to respective absorbance peaks of oil; and
a third narrow bandpass filter of the set of three narrow bandpass filters comprises a CO 2 filter and is configured to preferentially transmit mid-infrared radiation over a band of wavelengths corresponding to respective absorbance peaks of CO 2 ;
one or more infrared detector(s) configured to detect filtered mid-infrared radiation transmitted through the set of three narrow bandpass filters; and a processor arrangement, operably coupled to the one or more infrared detector(s) and configured to measure intensities of the detected mid-infrared radiation transmitted through the set of three narrow bandpass filters and determine therefrom an amount of CO 2 in the fluid, notwithstanding whether the fluid contacting the window is a liquid water-based phase, a liquid oil-based phase, a mixture of liquid water- and liquid oil-based phases, or a gas phase.

2 . The sensor according to claim 1 , wherein the first, second, and third narrow bandpass filters of the set of three narrow bandpass filters preferentially transmit mid-infrared radiation over bands of wavelengths corresponding to absorbance peaks of about 3330 cm- 1 for water, about 2900 cm- 1 for oil, and about 2340 cm- 1 for CO 2 .

3 . The sensor according to claim 1 , wherein, to determine the amount of CO 2 in the fluid, the processor arrangement calculates the phase of the fluid from the measured intensities of the mid-infrared radiation transmitted through the water and oil filters, and then calculates from the phase of the fluid and the measured intensity of the mid-infrared radiation transmitted through the CO 2 filter the amount of CO 2 in the fluid.

4 . The sensor according to claim 3 , wherein the processor arrangement uses the refractive index of the fluid, derived from the phase of the fluid, in the calculation of the amount of CO 2 in the fluid.

5 . The sensor according to claim 1 , wherein each narrow bandpass filter of the set of three narrow bandpass filters is configured such that its wavelength transmission band is substantially temperature invariant over all temperatures in the range from about 25° C. to about 150° C.

6 . The sensor according to claim 5 , wherein each of the narrow bandpass filters comprises an interference filter having a substrate and at each opposing side of the substrate alternating high and low refractive index layers.

7 . The sensor according to claim 1 , further comprising:
a reference narrow bandpass filter configured to transmit mid-infrared radiation over a band of wavelengths corresponding to a reference portion of the absorbance spectrum of the fluid, wherein the or a further infrared detector is configured to detect filtered mid-infrared radiation transmitted through the reference filter, and wherein the processor arrangement is configured to measure a reference intensity of the detected mid-infrared radiation transmitted through the reference filter and use the measured reference intensity in the determination of the amount of the CO 2 in the fluid.

8 . The sensor according to claim 1 , wherein the beam of mid-infrared radiation is pulsed.

9 . The sensor according to claim 1 , wherein the window comprises one of a diamond window or a sapphire window.

10 . The sensor according to claim 1 , further comprising:
a heater configured to heat the window and cleaning a surface of the window in contact with the fluid.

11 . The sensor according to claim 1 , further comprising:
a pressure pulse arrangement configured to produce a pressure pulse in the fluid at the window and clean the surface of the window in contact with the fluid.

12 . (canceled)

13 . (canceled)

14 . A method of monitoring CO 2 in a fluid, the method comprising:
providing the sensor of claim 1 such that the internal reflection window is in direct contact with the fluid; and operating the sensor to determine an amount of CO 2 in the fluid.

15 . A method of determining an amount of CO 2 in a fluid, the method comprising:
receiving respective measured intensities of mid-infrared radiation filtered by three narrow bandpass filters which preferentially transmit mid-infrared radiation over bands of wavelengths corresponding to respective absorbance peaks of water, oil, and CO 2 , the mid-infrared radiation, prior to filtering, being produced by directing a beam of mid-infrared radiation into an internal reflection window for attenuated internal reflection at an interface between the window and a fluid in direct contact with window; calculating from the measured intensities of the mid-infrared radiation filtered by the water and oil filters the phase of the fluid; and calculating from the phase of the fluid and the measured intensity of the mid-infrared radiation filtered by the CO 2 filter the amount of CO 2 in the fluid.

16 . A well tool including the sensor of claim 1 .

17 . A method for detecting or measuring CO 2 in a fluid, the method comprising:
directing a beam of mid-infrared radiation into a window in contact with the fluid; passing an attenuated internal reflection of the beam of mid-infrared radiation at an interface between the window and the fluid through a set of three narrow bandpass filters configured to filter the internally reflected mid-infrared radiation received from the window wherein:
a first narrow bandpass filter of the set of three narrow bandpass filters comprises a water filter and is configured to preferentially transmit mid-infrared radiation over a band of wavelengths corresponding to respective absorbance peaks of water;
a second narrow bandpass filter of the set of three narrow bandpass filters comprises an oil filter and is configured to preferentially transmit mid-infrared radiation over a band of wavelengths corresponding to respective absorbance peaks of oil; and
a third narrow bandpass filter of the set of three narrow bandpass filters comprises a CO 2 filter and is configured to preferentially transmit mid-infrared radiation over a band of wavelengths corresponding to respective absorbance peaks of CO 2 ;
using one or more infrared detector(s) to detect the mid-infrared radiation passing through each of the set of three narrow bandpass filters; measuring intensities of the detected mid-infrared radiation passed through the set of three narrow bandpass filters; and determining an amount of CO 2 in the fluid from the measured intensities, wherein the fluid contacting the window is one or more of a liquid water-based phase, a liquid oil-based phase, a mixture of liquid water and liquid oil-based phases, or a gas phase.

Assignees

• Schlumberger Technology Corp

Inventors

• Fujisawa Go
• Chao Sheng
• Jones Timothy
• Lawrence Nathan
• Rustad Rolf
• Jiang Li
• Gahlings Steven

Classifications

• G01V8/10 Primary

  Detecting, e.g. by using light barriers (by reflection from the object G01S17/00) · CPC title

• G01N21/15

  Preventing contamination of the components of the optical system or obstruction of the light path · CPC title

• E21B49/08

  Obtaining fluid samples or testing fluids, in boreholes or wells · CPC title

• G01N21/3504 Primary

  for analysing gases, e.g. multi-gas analysis · CPC title

• G01N2201/0696

  Pulsed · CPC title