NMR measurement of wax appearance in fluids

• US 7,688,071 B2
• Filed: 10/16/2007
• Issued: 03/30/2010
• Est. Priority Date: 01/31/2007
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Cheng, Yuesheng, Kharrat, Abdel M.
• Primary Examiner(s): Shrivastav; Brij B.
• Assistant Examiner(s): Fetzner; Tiffany A
• Application Number:
  US11/872,906
• Publication Number:
  US 20090066330A1
• Time in Patent Office: 896 Days
• Field of Search: 324300-322, 324336-343, 600407-435
• US Class Current: 324/321
• CPC Class Codes: G01N 24/08 by using nuclear magnetic resonance G01N24/12 takes precedence
• CPC Class Codes: G01N 24/081 Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity
• CPC Class Codes: G01R 33/307 specially adapted for moving the sample relative to the MR system, e.g. spinning mechanisms, flow cells or means for positioning the sample inside a spectrometer
• CPC Class Codes: G01R 33/50 based on the determination of relaxation times , e.g. T1 measurement by IR sequences; T2 measurement by multiple-echo sequences
• CPC Class Codes: G01R 33/5617 using RF refocusing, e.g. RARE
• CPC Class Codes: G01V 3/32 operating with electron or nuclear magnetic resonance

Abstract

A method for determining a wax appearance temperature of a fluid includes obtaining nuclear magnetic resonance (NMR) measurements of the fluid at a plurality of temperatures; deriving a NMR parameter from each of the NMR measurements; and determining the wax appearance temperature by analyzing the NMR parameter as a function of temperature. An apparatus for detecting wax appearance in a fluid includes a sample cell for holding a fluid for nuclear magnetic resonance (NMR) measurements at a plurality of temperatures; a temperature measuring device disposed proximate the sample cell; a magnet for polarizing molecules in the fluid in the sample cell; at least one radiofrequency (RF) coil for generating pulses of magnetic field and for detecting NMR signals; and circuitry for controlling and measuring the temperature of the fluid in the sample cell and for obtaining NMR measurements.

Claims

1. A method for determining the wax appearance temperature of a fluid comprising:

obtaining nuclear magnetic resonance (NMR) measurements of the fluid at a plurality of fluid temperatures;

deriving an NMR parameter from each of the NMR measurements; and

determining the wax appearance temperature of the fluid by analyzing the NMR parameter as a function of fluid temperature.

2. The method of claim 1, wherein the NMR parameter is one selected from the group consisting of T₁, a logarithmic mean of T₁ distribution, T₂, a logarithmic mean of T₂ distribution, T_1/T₂, diffusion constant (D), a logarithmic mean of diffusion constants, and NMR signal intensity.

3. The method of claim 1, wherein the NMR parameter is a logarithmic mean of T₂ or T_1/T₂.

4. The method of claim 1, wherein the NMR parameter is a diffusion constant or a logarithmic mean of diffusion constant distribution.

5. The method of claim 1, wherein the NMR parameter is NMR signal intensity.

6. A nuclear magnetic resonance (NMR) apparatus that detects wax appearance in a fluid, comprising:

a sample cell configured for holding a fluid while NMR measurements are performed at a plurality of temperatures;

a temperature measuring device disposed proximate the sample cell;

a magnet configured for polarizing molecules within the fluid in the sample cell;

at least one radiofrequency (RF) coil configured for generating pulses of magnetic field and configured for detecting NMR signals; and

circuitry configured for controlling and measuring the temperature of the fluid in the sample cell and configured for obtaining NMR measurements.

7. The NMR apparatus of claim 6, wherein the sample cell has an inlet and an outlet such that it measures the fluid flowing therethrough.

8. The NMR apparatus of claim 6, further comprising a thermocouple disposed ill the sample cell that measures the temperature of the fluid therein.

9. Tile NMR apparatus of claim 6, wherein tile apparatus is configured to be used on a pipeline.

10. The NMR apparatus of claim 6, wherein the apparatus is configured to be used on a downhole tool.