Determining continuous capillary pressure curves for subsurface earth formations using saturation and NMR log data

Patent metadata

Field	Value
Publication number	US-9671525-B2
Application number	US-201313790619-A
Country	US
Kind code	B2
Filing date	Mar 8, 2013
Priority date	Mar 8, 2013
Publication date	Jun 6, 2017
Grant date	Jun 6, 2017

Abstract

Continuous capillary pressure (P c ) curves of subsurface rock formations adjacent wells are determined based on translation relaxation time (T 2 ) data from nuclear magnetic resonance (NMR) and from wireline well logs, such as resistivity logs, to obtain water saturation (S w ) of the rock in the formations. The T 2 data and the hydrocarbon density, water density, free water level, and paleo-water level of the formation are processed to obtain parameters of Thomeer hyperbolas that closely conform to water saturation values obtained from the other well logs. The Thomeer hyperbolas so determined are converted to capillary pressure curves.

First claim

What is claimed is:

1. A computer implemented method of obtaining measures in a data processing system of capillary pressure of pore systems in formation rock adjacent a well in a subsurface reservoir at a formation depth point of interest in the well, the method comprising the computer processing steps of:
(a) receiving nuclear magnetic resonance well log data comprising transverse relaxation time amplitude distribution obtained from the formation by a nuclear magnetic resonance log of the well at the formation depth point of interest;
(b) receiving resistivity well log data regarding the water saturation of the formation from measurements obtained from the formation by a resistivity well log of the well at the formation depth point of interest;
(c) obtaining a measure of water saturation of the formation from the received resistivity well log data at the formation depth point of interest;
(d) determining an initial measure of capillary pressure of the formation at the formation depth point of interest based on the received transverse relaxation time amplitude distribution;
(e) performing a calibration of the initial measure of capillary pressure of the formation to a reference capillary pressure of the formation rock at the depth point of interest, the calibration being perform based on the measure of water saturation obtained from the received resistivity well log data from the formation at the depth point of interest;
(f) forming a model of capillary pressure as a function of water saturation at the formation at the depth of interest;
(g) testing the model of capillary pressure, and if the model of capillary pressure is acceptable, storing the tested model capillary pressure as the capillary pressure of the formation pore systems at the depth of interest; and
(h) forming an output display of the accepted capillary pressure of the formation pore systems at the depth of interest for reservoir simulation.

2. The computer implemented method of claim 1 , wherein the step of receiving nuclear magnetic resonance well log data comprises the step of:
receiving nuclear magnetic resonance well log data regarding a plurality of depths of interest in the formation.

3. The computer implemented method of claim 2 , wherein the step of receiving resistivity well log data regarding the water saturation of the formation comprises the step of:
receiving resistivity well log data regarding the water saturation at a plurality of depths of interest in the formation.

4. The computer implemented method of claim 3 , wherein the step of determining an initial measure of capillary pressure of the formation comprises the step of:
determining an initial measure of capillary pressure of the formation at a plurality of depths of interest in the formation.

5. The computer implemented method of claim 4 , wherein the step of performing a calibration of the initial measure of capillary pressure comprises the step of:
performing a calibration of the initial measure of capillary pressure at a plurality of depths in the formation to a postulated capillary pressure at a plurality of depths in the formation.

6. The computer implemented method of claim 5 , further including the step of:
storing a record of the postulated capillary pressure at a plurality of depths in the formation.

7. The computer implemented method of claim 6 , further including the step of:
forming an output display of the postulated capillary pressure at a plurality of depths in the formation.

8. The computer implemented method of claim 1 , wherein the accepted capillary pressure of the formation pore systems at the depth of interest comprises formation cumulative bulk percentage and entry pressure.

9. A data processing system for obtaining measures in a data processing system of capillary pressure of pore system in formation rock adjacent a well in a subsurface reservoir at a formation depth point of interest in the well, the data processing system comprising:
(a) a processor performing the steps of:
(1) receiving nuclear magnetic resonance well log data comprising transverse relaxation time amplitude distribution obtained from the formation by a nuclear magnetic resonance log of the well at the formation depth point of interest;
(2) receiving resistivity well log data regarding the water saturation of the formation from measurements obtained from the formation by a resistivity well log of the well at the formation depth point of interest;
(3) obtaining a measure of water saturation of the formation from the received resistivity well log data at the formation depth point of interest;
(4) determining an initial measure of capillary pressure of the formation at the formation depth point of interest based on the received transverse relaxation time amplitude distribution;
(5) performing a calibration of the initial measure of capillary pressure of the formation to a reference capillary pressure of the formation rock at the formation depth point of interest, the calibration being performed based on the measure of water saturation obtained from the received resistivity well log data from the formation at the depth point of interest;
(6) forming a model of capillary pressure as a function of water saturation at the formation at the depth of interest;
(7) testing the model of capillary pressure, and if the model of capillary pressure is acceptable, storing the tested model capillary pressure as the capillary pressure of the formation pore systems at the depth of interest; and

(b) an output display forming a display of accepted capillary pressure of the formation pore systems at the depth of interest for reservoir simulation.

10. The data processing system of claim 9 , wherein the processor in receiving nuclear magnetic resonance well log data from measurements obtained from the formation by nuclear magnetic resonance log from the well performs the step of:
receiving nuclear magnetic resonance well log data regarding a plurality of depths of interest in the formation.

11. The data processing system of claim 10 , wherein the processor in receiving resistivity well log data regarding the water saturation of the formation performs the step of:
receiving resistivity well log data regarding the water saturation at a plurality of depths of interest in the formation.

12. The data processing system of claim 11 , wherein the processor in determining an initial measure of capillary pressure of the formation performs the step of:
determining an initial measure of capillary pressure of the formation at a plurality of depths of interest in the formation.

13. The data processing system 12 , wherein the processor in performing a calibration of the initial measure of capillary pressure performs the step of:
performing a calibration of the initial measure of capillary pressure at a plurality of depths in the formation to a postulated capillary pressure at a plurality of depths in the formation.

14. The data processing system of claim 13 , wherein the output display forms an output display of the postulated capillary pressure at a plurality of depths in the formation.

15. The data processing system of claim 9 , further including:
a memory storing a record of the accepted capillary pressure of the formation pore systems at the depth of interest for reservoir simulation.

16. The data processing system of claim 9 , wherein the accepted capillary pressure of the formation pore systems at the depth of interest comprises formation cumulative bulk percentage and entry pressure.

17. A data storage device having stored in a computer readabl

Assignees

• Saudi Arabian Oil Co

Inventors

• Al-Ibrahim Mustafa
• Mezghani Mokhles Mustapha
• Buiting Johannes Jacobus

Classifications

• G01V9/02 Primary

  Determining existence or flow of underground water · CPC title

• G01V3/32

  operating with electron or nuclear magnetic resonance · CPC title

• G01V11/00

  Prospecting or detecting by methods combining techniques covered by two or more of main groups G01V1/00 - G01V9/00 · CPC title

• G01V3/14 Primary

  operating with electron or nuclear magnetic resonance · CPC title

• Y02A90/30

  Assessment of water resources · CPC title