Petrophysically regularized time domain NMR inversion

Patent metadata

Field	Value
Publication number	US-10353107-B2
Application number	US-201214355498-A
Country	US
Kind code	B2
Filing date	Oct 31, 2012
Priority date	Oct 31, 2011
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

A petrophysically regularized time domain nuclear magnetic resonance (NMR) inversion includes using an NMR tool to acquire NMR data and inverting the acquired NMR data in a time domain using petrophysical constraints. The inverted NMR data is analyzed. The petrophysical constraints may be identified by: determining a number of porobodons to seek, defining a plurality of zones in which only a subset of porobodon sets is present, and stacking all NMR echoes in each zone satisfying discriminators. The number of porobodons to seek may be based on knowledge of core samples, logs, and NMR sensitivity. The discriminator logs may be logs sensitive to porosity partitioning. A computing system having a processor, a memory, and a program stored in memory may be configured to perform the method. The system may be conveyed downhole on a wireline, a while-drilling drill string, a coiled tubing, a slickline, or a wired drill pipe.

First claim

What is claimed is:

1. A method, comprising:
using a nuclear magnetic resonance (NMR) tool to acquire NMR data from a wellbore traversing a subterranean formation, wherein the NMR data includes at least one of NMR distributions of T1, T2, or diffusion coefficient, and wherein petrophysical constraints comprise intervals for distribution parameters related to T1, T2, and diffusion;
inverting the acquired NMR data in a time domain using petrophysical constraints comprising

0
≤

a
k

≤

a

k
⁢

⁢
m
⁢

⁢
a
⁢

⁢
x

m

k
⁢

⁢
m
⁢

⁢
i
⁢

⁢
n

≤

m
k

≤

m

k
⁢

⁢
m
⁢

⁢
a
⁢

⁢
x

a

k
⁢

⁢
m
⁢

⁢
a
⁢

⁢
x

∈

{

0
,

+
∞

}

,

k
=
1

,

…
⁢

⁢
NG

,

σ

k
⁢

⁢
m
⁢

⁢
i
⁢

⁢
n

≤

σ
k

≤

σ

k
⁢

⁢
m
⁢

⁢
a
⁢

⁢
x

wherein a k are porobodon amplitudes, m k are porobodon positions, σ k are porobodon widths, and NG is a number of porobodons;
analyzing the inverted NMR data to determine a characteristic of a fluid in the subterranean formation; and
using the determined characteristic of the fluid in the subterranean formation in an oilfield operation or evaluation.

2. The method of claim 1 , wherein inverting the acquired NMR data is applied to a one-dimensional distribution of a relaxation time T1, a relaxation time T2, or a diffusion coefficient; a multi-dimensional distribution of the relaxation time T1, the relaxation time T2, and the diffusion coefficient; or a subset of those distributions.

3. The method of claim 2 , wherein the subset of those distributions includes a distribution based on a priori petrophysical knowledge.

4. The method of claim 2 , wherein the subset of those distributions includes linear superpositions of log-normal distributions for the relaxation time T1 and the relaxation time T2 and a normal distribution for the diffusion coefficient.

5. The method of claim 1 , wherein inverting the acquired NMR data is performed according to the equations:

log
⁡

(

T

2
⁢
j

)

Assignees

• Schlumberger Technology Corp
• Saudi Arabian Oil Co

Inventors

• Allen David F
• Bordakov George
• Crary Steve F
• Savundararaj Philip
• Eyvazzadeh Ramsin
• Clerke Edward Alan
• Buiting Johannes J
• Smith Paul
• Funk Jim

Classifications

• G01V3/32 Primary

  operating with electron or nuclear magnetic resonance · CPC title

• G01R33/4625

  Processing of acquired signals, e.g. elimination of phase errors, baseline fitting, chemometric analysis · CPC title

• G01N24/081

  Making measurements of geologic samples, e.g. measurements of moisture, pH, porosity, permeability, tortuosity or viscosity · CPC title

• G01R33/44

  using nuclear magnetic resonance [NMR] (G01R33/24, G01R33/62 take precedence) · CPC title