METHOD FOR CONTINUOUS INTERPRETATION OF MONITORING DATA

• US 20080065332A1
• Filed: 11/05/2007
• Published: 03/13/2008
• Est. Priority Date: 06/04/2004
• Status: Active Grant

• Current Assignee: Bhavani Raghuraman, Terizhandur Ramakrishnan
• Original Assignee: Bhavani Raghuraman, Terizhandur Ramakrishnan
• Inventors: Raghuraman, Bhavani, Ramakrishnan, Terizhandur
• Granted Patent: US 7,715,984 B2
• Time in Patent Office: Days
• US Class Current: 702/11
• CPC Class Codes: G01V 1/40 specially adapted for well-logging

Abstract

It is shown that a pressure pulse originating in a well is correlated to a pulse observed at a distant well with a characteristic time. The correlation time is directly related to the diffusion time scale arising out of the pressure diffusion equation. The relationship is affected by the source-observer or observer-observer distance but the correction is small for large distances. In practice, further corrections have to be included for finite width pulses. For these pulses, a practical scheme for continuous permeability monitoring is presented.

Claims

1. A method for monitoring characteristics of a region of earth formation over time, comprising:

a. obtaining source pressure pulses at at least one location in a source well;

b. obtaining observer pressure data at at least one location in an observer well, wherein said observer data may be correlated to said source data;

c. repeating (a) and (b) one or more times;

d. developing a correlation between said source data and said observer data as a function of time, wherein said correlation is based on a propagation function governed by pressure diffusion;

e. determining the time location of the maximum value of said correlation and analyzing the decay of said maximum value over time.

f. analyzing said correlation to monitor at least the permeability of said earth formation; and

g. storing said data.

2. The method of claim 1, further comprising correcting said correlation time for storage effects at said source well.

3. The method of claim 1, further comprising correcting said correlation time for the distance between said observer well and said source well.

4. The method of claim 1, further comprising correcting said correlation time for the width of said pressure pulses.

5. A method of monitoring permeability of a region of earth formation over time comprising:

a. inducing one or more pressure pulses at at least one location in at least one source well, wherein data on said induced pressure pulses is gathered;

b. measuring pressure pulse data at at least one location in at least one observer well, wherein said pressure pulse data includes pressure pulses having diffused through at least a portion of said earth formation;

c. repeating (a) and (b) one or more times;

d. developing a correlation between said induced pressure pulses and said diffused pressure pulses as a function of time; and

e. analyzing said correlation to monitor the permeability the region of earth formation.

6. The method of claim 5, wherein said correlation is based on a propagation function governed by pressure diffusion.

7. The method of claim 5, further comprising analyzing the shape of said correlation over time.

8. The method of claim 5, further comprising determining the determining the time location of the maximum value of said correlation and analyzing the decay of said maximum value over time.

9. The method of claim 8, wherein said correlation is governed by pressure diffusion, and wherein at least one of said one or more characteristics is permeability.

10. The method of claim 5, wherein said induced pressure pulse data gathered at the source well and said diffused pressure pulsed data gathered at the observer well is differentiated pressure data.

11. The method of claim 5, wherein said induced pressure pulse data is flow data and said diffused pressure pulse is pressure data.

12. The method of claim 5, further comprising repeating (a), (b) and (c) for more than one observer well.

13. The method of claim 5, further comprising repeating (a), (b), and (c) for more than one source well.

14. The method of claim 10, further comprising correcting said correlation time for storage effects at said source well.

15. The method of claim 10, further comprising correcting said correlation time for the distance between said observer well and said source well.

16. The method of claim 10, further comprising correcting said correlation time for the width of said induced pressure pulses.