Estimating adsorbed gas volume from NMR and dielectric logs

Patent metadata

Field	Value
Publication number	US-9753176-B2
Application number	US-201313767721-A
Country	US
Kind code	B2
Filing date	Feb 14, 2013
Priority date	Feb 14, 2013
Publication date	Sep 5, 2017
Grant date	Sep 5, 2017

Abstract

Adsorbed gas in a formation may be estimated. Nuclear magnetic resonance (NMR) data for a subsurface geological formation is obtained, and at least a portion of the NMR data is corrected to produce corrected NMR data. A NMR-based estimate of formation porosity is determined using the corrected NMR data. Dielectric permittivity data for the subsurface geological formation is obtained, and a dielectric permittivity-based estimate of the formation water-filled porosity is determined using the dielectric permittivity data. A gas volume is determined using the determined NMR-based estimate of the formation porosity and the determined dielectric permittivity-based estimate of the formation water-filled porosity. The gas volume may be determined by subtracting the determined dielectric permittivity-based estimate of the formation water-filled porosity from the determined NMR-based estimate of the formation porosity. The gas volume per unit volume of the formation may be determined using an equation of state.

First claim

What is claimed is:

1. A method, comprising:
placing an NMR system downhole;
obtaining nuclear magnetic resonance (NMR) data for a subsurface geological formation;
correcting at least a portion of the NMR data to produce corrected NMR data;
determining a NMR-based estimate of formation porosity using the corrected NMR data;
obtaining dielectric permittivity data for the subsurface geological formation;
determining a dielectric permittivity-based estimate of the formation water-filled porosity using the dielectric permittivity data; using the determined estimates for a more efficient drilling or production operation;
in one or more processors, determining a gas volume using the determined NMR-based estimate of the formation porosity and the determined dielectric permittivity-based estimate of the formation water-filled porosity; and
using the determined estimates for a more efficient drilling or production operation;
wherein the formation water-filled porosity indicates a percentage of pore volume of the subsurface geological formation filled with water.

2. The method of claim 1 , wherein the correcting at least a portion of the NMR data comprises correcting a short transverse relaxation time (T2) portion of the NMR data.

3. The method of claim 2 , wherein the correcting at least a short transverse relaxation time (T2) portion of the NMR data comprises weighting the T2 distribution.

4. The method of claim 2 , wherein the correcting at least a short transverse relaxation time (T2) portion of the NMR data comprises accounting for the signal-to-noise ratio of the T2 distribution.

5. The method of claim 1 , wherein the correcting at least a portion of the NMR data comprises weighting an estimated porosity obtained from inverting the NMR data.

6. The method of claim 1 , wherein the determining a gas volume using the determined NMR-based estimate of the formation porosity and the determined dielectric permittivity-based estimate of the formation water-filled porosity comprises subtracting the determined dielectric permittivity-based estimate of the formation water-filled porosity from the determined NMR-based estimate of the formation porosity.

7. The method of claim 1 , further comprising making a steering decision for an LWD tool based on the determined gas volume.

8. The method of claim 1 , further comprising planning a fracturing operation based on the determined gas volume.

9. The method of claim 1 , further comprising planning a well completion based on the determined gas volume.

10. The method of claim 1 , further comprising determining an economic viability for a formation based on the determined gas volume.

Assignees

• Schlumberger Technology Corp

Inventors

• Datey Ashish
• Hopper Timothy Andrew John
• Venkataramanan Lalitha

Classifications

• G01V3/26

  operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device (with electromagnetic waves G01V3/30) · CPC title

• G01V3/32 Primary

  operating with electron or nuclear magnetic resonance · CPC title

• E21B47/00

  Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) · CPC title

• Y02A90/30

  Assessment of water resources · CPC title