Method and apparatus for detecting naphthenic acids

• US 7,750,302 B2
• Filed: 09/09/2008
• Issued: 07/06/2010
• Est. Priority Date: 09/09/2008
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Jamaluddin, Abul K. M., Mullins, Oliver C., Vannuffelen, Stephane
• Primary Examiner(s): Porta; David P
• Assistant Examiner(s): Baker; David S
• Application Number:
  US12/206,805
• Publication Number:
  US 20100059669A1
• Time in Patent Office: 665 Days
• Field of Search: 250/253, 250/256, 250/258, 250/269.1, 250/265, 250/339.11, 250/341.8, 250/254, 250/255, 250/257, 250/259, 250/339.12, 250/343, 356/70, 731/52
• US Class Current: 250/339.12
• CPC Class Codes: E21B 49/08 Obtaining fluid samples or testing fluids, in boreholes or wells

Abstract

A method and apparatus for determining the concentration of organic acids in formation fluids is provided including pumps for pumping fluids from a subterranean formation into the body of a downhole tool and sources for illuminating the flow with infrared radiation to obtain the infrared absorption or a related parameter at one or more wavelengths, and processors for converting the measured absorption into the concentration of the organic acids, using for example a multi-value calibration matrix which relates IR absorption spectral values to concentration measurement under downhole conditions.

Claims

1. A method of determining the concentration of naphthenic acids in formation fluids, said method comprising the steps of:

allowing said formation fluids to flow through a body of a downhole tool;

radiating said flow with infrared radiation to obtain infrared absorption parameters at one or more wavelengths under downhole conditions, and

determining the concentration of said naphthenic acid by converting said absorption parameters.

2. The method of claim 1 wherein the infrared radiation is radiation in the mid-IR range of 30 μ

m-1.4 μ

m.

3. The method of claim 1 wherein the infrared radiation is transmitted through the flow.

4. The method of claim 1 wherein the infrared radiation is reflected from an interface with the flow.

5. The method of claim 1 wherein the absorption parameters are converted into concentrations using a calibration derived from absorption values of mixtures with known concentrations of the naphthenic acid.

6. The method of claim 1 further comprising the step of determining the concentrations of the naphthenic acid and of hydrocarbons in the fluid.

7. The method of claim 1 further comprising the step of determining the total acid number (TAN) of the fluid.

8. An apparatus for determining the concentration of naphthenic acids in formation fluids, said apparatus comprising

a flow line for allowing said formation fluids to flow from a downhole formation through a body of said apparatus at a downhole location;

one or more sources of infrared radiation for radiating flow in said flow line with infrared radiation;

one or more detectors to obtain absorption parameters at one or more wavelengths under downhole conditions, and

a processor for determining the concentration of said naphthenic acid by converting said absorption parameters.

9. The apparatus of claim 8 wherein the infrared radiation is radiation in the mid-IR range of 30 μ

m-1.4 μ

m.

10. The apparatus of claim 8 wherein the infrared radiation is transmitted through the flow.

11. The apparatus of claim 8 wherein the infrared radiation is reflected from an interface with the flow.

12. The apparatus of claim 8 wherein the absorption parameters are converted into concentrations using a calibration derived from absorption values of mixtures with known concentrations of the naphthenic acid.