Pulse fracturing device and method

• US 8,220,537 B2
• Filed: 11/25/2008
• Issued: 07/17/2012
• Est. Priority Date: 11/30/2007
• Status: Active Grant

• Current Assignee: Chevron USA Incorporated (Chevron Corp.)
• Original Assignee: Chevron USA Incorporated (Chevron Corp.)
• Inventors: Fram, Joseph Henry, Leon, Jean-Francois
• Primary Examiner(s): Bagnell, David
• Assistant Examiner(s): Wallace, Kipp
• Application Number:
  US12/277,515
• Publication Number:
  US 20090294121A1
• Time in Patent Office: 1,330 Days
• Field of Search: 166/259, 166/308.1, 166/272.1, 166/281, 166/177.5
• US Class Current: 166/177.5
• CPC Class Codes: E21B 28/00 Vibration generating arrangements for boreholes or wells, e.g. for stimulating production for fishing for or freeing objects E21B31/005; for transmitting measuring-signals E21B47/14; for geophysical measurements G01V1/02
• CPC Class Codes: E21B 33/124 Units with longitudinally-spaced plugs for isolating the intermediate space
• CPC Class Codes: E21B 43/003 Vibrating earth formations
• CPC Class Codes: E21B 43/2405 in association with fracturing or crevice forming processes E21B43/247 takes precedence
• CPC Class Codes: E21B 43/26 by forming crevices or fractures
• CPC Class Codes: G01V 1/157 using spark discharges; using exploding wires

Abstract

A method of inducing fracture in at least a portion of a geologic structure includes inducing acoustic waves into a fluid medium present in a borehole extending at least partially into the structure. Embodiments may include preheating or pressurizing the fluid medium prior to inducing the acoustic wave therein. A device for fracturing at least a portion of a geologic structure includes electrodes for producing a spark to generate ordinary acoustic waves in the fluid medium. Embodiments may include structures for preheating or pressurizing the fluid medium prior to inducing the acoustic wave therein.

Claims

1. A method of inducing fracture in at least a portion of a geologic structure, comprising:

generating an acoustic wave in a fluid medium present in a borehole penetrating at least partially into the geologic structure, the acoustic wave being an ordinary acoustic wave and having frequency, duration and amplitude sufficient to induce fracture in the portion of the geologic structure and at least at a boundary between the fluid and the structure; and

injecting heated pressurized fluid into a region proximate an electrode used to generate the acoustic wave to create a temperature gradient in a portion of the fluid medium having a peak temperature below a boiling point of the fluid medium.

2. A method as in claim 1, wherein the fluid is injected through an aperture in the electrode.

3. A method as in claim 1, wherein the temperature below the boiling point of the fluid medium is within about 10% of the boiling point of the fluid medium.

4. A method as in claim 1, further comprising, prior to generating the pulsed acoustic wave, pressurizing the fluid in the borehole to a pressure below a threshold pressure above which the geologic structure would fracture.

5. A method as in claim 4, wherein the pressure below the threshold pressure is a pressure within about 10% of the threshold pressure.

6. A method as in claim 1, wherein the generating the acoustic wave comprises generating a spark discharge within the fluid to form an expanding gas bubble that exerts pressure on the fluid to generate the acoustic wave.

7. A method as in claim 1, further comprising, repeating the generating at a frequency below about 10 Hz.

8. A method as in claim 1, wherein:

the generating comprises generating a discharge within the fluid; and

a current of the discharge squared is greater than 3% of a peak value of the current of the discharge squared for more than 100 μ

s.

9. A method as in claim 1, further comprising injecting an agent into the fluid medium, the agent being selected to improve flowability of a material present in the geologic structure.

10. A method as in claim 9, wherein the agent comprises a chemical additive.

11. A method as in claim 10, wherein the chemical additive is an agent for inducing rock fracture.

12. A method as in claim 10, wherein the additive comprises steam.

13. A method as in claim 1, wherein the generating the acoustic wave comprises generating repeating spark discharges at a frequency below about 10 Hz to form expanding gas bubbles that create pressure impulses on the fluid.

14. A method as in claim 1, wherein the generating the acoustic wave comprises generating spark discharges with a pulsed rise time greater than about 100 μ

s.

15. A method as in claim 1, wherein the generating the acoustic wave comprises generating spark discharges at an energy of greater than about 100 kJ per pulse.