# US 9,753,176 B2 · Estimating adsorbed gas volume from NMR and dielectric logs

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- Number: US 9,753,176 B2
- Document ID: US9753176B2
- Status: Granted
- Kind: B2
- Application number: 13/767,721
- Filed: 2013-02-14
- Published: 2014-08-14
- Granted: 2017-09-05
- Earliest claimed: 2013-02-14
- Assignees: Schlumberger Technology Corporation
- Applicants: Schlumberger Technology Corporation
- Inventors: Ashish Datey; Timothy Andrew John Hopper; Lalitha Venkataramanan
- Web page: https://patentgrep.com/patent/US9753176B2

## CPC

- G01V 3/32: operating with electron or nuclear magnetic resonance
- E21B 47/00: Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08)
- G01V 3/26: 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)
- Y02A 90/30: Assessment of water resources
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE

## 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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 2)

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.

### Claim 4 (depends on 2)

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.

### Claim 5 (depends on 1)

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.

### Claim 6 (depends on 1)

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.

### Claim 7 (depends on 1)

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

### Claim 8 (depends on 1)

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

### Claim 9 (depends on 1)

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

### Claim 10 (depends on 1)

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