Planning and performing re-fracturing operations based on microseismic monitoring

Patent metadata

Field	Value
Publication number	US-9822626-B2
Application number	US-201514615033-A
Country	US
Kind code	B2
Filing date	Feb 5, 2015
Priority date	Feb 5, 2015
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

An embodiment of a method of stimulating an earth formation includes: disposing a stimulation device at a borehole in an earth formation, the earth formation having been stimulated by an initial stimulation operation; subsequent to the stimulation operation, performing a probe operation configured to cause movement of existing fractures in the formation; and measuring microseismic events occurring in the formation by one or more seismic receivers. The method further includes: identifying one or more target zones in the formation based on the measuring, the one or more target zones exhibiting a reduced micro seismicity relative to another zone in the formation; and designing a re-stimulation operation configured to stimulate the one or more target zones to increase hydrocarbon production from the formation.

First claim

The invention claimed is:

1. A method of stimulating an earth formation, comprising:
disposing a stimulation device at a borehole in an earth formation, the earth formation having been stimulated by an initial stimulation operation, the initial stimulation operation being an initial hydraulic fracturing operation that includes injection of a stimulation fluid into the formation at a pressure at least equal to a fracturing pressure of the formation;
subsequent to the stimulation operation, performing a probe operation configured to cause movement of existing fractures in the formation, wherein performing the probe operation includes injecting a treatment fluid into the formation at a pressure that is less than the fracturing pressure;
measuring microseismic events occurring in the formation by one or more seismic receivers;
identifying one or more target zones in the formation based on the measuring, the one or more target zones exhibiting a reduced microseismicity relative to another zone in the formation; and
designing a re-stimulation operation configured to stimulate the one or more target zones to increase hydrocarbon production from the formation.

2. The method of claim 1 , wherein:
performing the probe operation includes injecting a treatment fluid at a pressure sufficient to pressurize the formation and cause one or more existing fractures in the formation to slip without causing new fractures to form, and subsequently allowing the one or more existing fractures to relax;
measuring the microseismic events includes detecting seismic waves generated by at least the slip of the one or more existing fractures;
identifying the one or more target zones includes identifying at least one depletion zone based on the measured microseismic events, the at least one depletion zone having a greater concentration of microseismic events than the one or more target zones; and
designing the re-stimulation operation includes designing a stimulation device to inject stimulation fluid into the one or more target zones while preventing a substantial amount of treatment fluid from entering the at least one depletion zone.

3. The method of claim 1 , wherein the existing fractures include natural fractures and any fractures created or activated by the initial stimulation operation.

4. The method of claim 1 , wherein the stimulation fluid includes a proppant, and the treatment fluid does not include a proppant.

5. The method of claim 1 , further comprising performing the re-stimulation operation by injecting stimulation fluid at a pressure that is at least equal to the fracturing pressure, and directing the stimulation fluid to the one or more target zones while substantially preventing the stimulation fluid from flowing into the another zone.

6. The method of claim 1 , wherein measuring microseismic events includes detecting a plurality of seismic events occurring during and after the probe operation, and associating each seismic event with a location relative to the borehole.

7. The method of claim 6 , wherein identifying the one or more target zones includes differentiating the one or more target zones from one or more depletion zones, the one or more depletion zones having a high concentration of microseismic events therein relative to the one or more target zones.

8. The method claim 7 , further comprising performing the re-stimulation operation disposing a stimulation device in the borehole, activating the stimulation device to isolate the one or more depletion zones, and injecting stimulation fluid into the one or more target zones at a pressure that is at least equal to a fracturing pressure of the formation.

9. A system for stimulating an earth formation, comprising:
a stimulation device configured to be disposed at a borehole in an earth formation, the earth formation having been stimulated by an initial stimulation operation, the initial stimulation operation being an initial hydraulic fracturing operation that includes injection of a stimulation fluid into the formation at a pressure at least equal to a fracturing pressure of the formation;
a microseismic monitoring system including one or more seismic receivers; and
a processor configured to perform:
subsequent to the stimulation operation, performing a probe operation via the stimulation device to cause movement of existing fractures in the formation, wherein performing the probe operation includes injecting a treatment fluid into the formation at a pressure that is less than the fracturing pressure;
measuring microseismic events occurring in the formation by the one or more seismic receivers;
identifying one or more target zones in the formation based on the measuring, the one or more target zones exhibiting a reduced microseismicity relative to another zone in the formation; and
designing a re-stimulation operation configured to stimulate the one or more target zones to increase hydrocarbon production from the formation.

10. The system of claim 9 , wherein:
performing the probe operation includes injecting a treatment fluid at a pressure sufficient to pressurize the formation and cause one or more existing fractures in the formation to slip without causing new fractures to form, and subsequently allowing the one or more existing fractures to relax;
measuring the microseismic events includes detecting seismic waves generated by at least the slip of the one or more existing fractures;
identifying the one or more target zones includes identifying at least one depletion zone based on the measured microseismic events, the at least one depletion zone having a greater concentration of microseismic events than the one or more target zones; and
designing the re-stimulation operation includes designing a stimulation device to inject stimulation fluid into the one or more target zones while preventing a substantial amount of treatment fluid from entering the at least one depletion zone.

11. The system of claim 9 , wherein the existing fractures include natural fractures and any fractures created or activated by the initial stimulation operation.

12. The system of claim 9 , wherein the stimulation fluid includes a proppant, and the treatment fluid does not include a proppant.

13. The system of claim 9 , wherein the processor is further configured to perform the re-stimulation operation by injecting stimulation fluid at a pressure that is at least equal to the fracturing pressure, and directing the stimulation fluid to the one or more target zones while substantially preventing the stimulation fluid from flowing into the another zone.

14. The system of claim 9 , wherein measuring microseismic events includes detecting a plurality of seismic events occurring during and after the probe operation, and associating each seismic event with a location relative to the borehole.

15. The system of claim 14 , wherein identifying the one or more target zones includes differentiating the one or more target zones from one or more depletion zones, the one or more depletion zones having a high concentration of microseismic events therein relative to the one or more target zones.

16. The system claim 15 , wherein the processor is further configured to perform the re-stimulation operation by disposing a stimulation device in the borehole, activating the stimulation device to isolate the one or more depletion zones, and injecting stimulation fluid into the one or more target zones at a pressure that is at least equal to a fracturing pressure of the formation.

Assignees

• Dumoit Jeremy
• Katz David
• Hurt Robert
• Baker Hughes A Ge Co Llc

Inventors

• Dumoit Jeremy
• Katz David
• Hurt Robert

Classifications

• G01V2210/1425

  Land surface · CPC title

• G01V1/42

  using generators in one well and receivers elsewhere or vice versa (G01V1/52 takes precedence) · CPC title

• G01V2210/646

  Fractures · CPC title

• E21B43/267 Primary

  reinforcing fractures by propping · CPC title

• G01V1/30

  Analysis (G01V1/50 takes precedence) · CPC title