System and Methods for Controlled Fracturing in Formations

• US 20150167439A1
• Filed: 12/12/2014
• Published: 06/18/2015
• Est. Priority Date: 12/13/2013
• Status: Active Grant

• Current Assignee: Chevron USA Incorporated (Chevron Corp.)
• Original Assignee: Chevron USA Incorporated (Chevron Corp.)
• Inventors: Kasevich, Raymond Stanley, Rong, Jeb Xiaobing, Koffer, James Preston, Looney, Mark Dean, Rijken, Margaretha Catharina Maria
• Granted Patent: US 9,890,627 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: E21B 33/124 Units with longitudinally-spaced plugs for isolating the intermediate space
• CPC Class Codes: E21B 43/006 Production of coal-bed methane E21B43/243 takes precedence
• CPC Class Codes: E21B 43/168 Injecting a gaseous medium
• CPC Class Codes: E21B 43/24 using heat, e.g. steam injection
• CPC Class Codes: E21B 43/26 by forming crevices or fractures
• CPC Class Codes: E21B 7/15 of electrically generated heat

Abstract

Controlled fracturing in geologic formations is carried out in a method employing a combination of alternating and impulsive current waveforms, applied in succession to achieve extensive fracturing and disintegration of rock materials for liquid and gas recovery. In a pre-conditioning step, high voltage discharges and optionally with highly ionizable gas injections are applied to a system of borehole electrodes, causing the formation to fracture with disintegration in multiple directions but confined between the locations of electrode pairs of opposite polarity. After pre-conditioning, intense current waveform of pulse energy is then applied to the system of borehole electrodes to create waves of ionization or shock waves with bubbles of heated gas that propagate inside and outside the high conductivity channels, resulting in rock disintegration with attendant large scale multiple fracturing.

Claims

1. A method of generating fractures in geologic formation, the method comprising:

providing a plurality of boreholes in the formation;

placing a plurality of electrodes in the boreholes with one electrode per borehole, with the plurality of electrodes defining a fracture pattern for the geologic formation;

applying a sufficient amount of energy to the electrodes to generate a least a conductive channel between a pair of electrodes, wherein the conductivity in the channel between the pair of electrodes is defined has a ratio of final to initial channel conductivity of 10;

1 to 50,000;

1; and

applying electrical impulses to the electrodes, the electrical impulses having a voltage output ranging from 100-2000 kV, an energy output of 10-1000 kJ, wherein the pulses have a rise time ranging from 0.05-500 microseconds and a half-value time of 50-5000 microseconds;

wherein the application of the electrical pulses generates multiple fractures within and about the conductive channel by disintegration of minerals and pyrolysis of organic materials in the formation.

2. The method of claim 1, wherein the sufficient amount of energy applied to the electrodes to generate the conductive channel is selected from electromagnetic conduction, radiant energy and combinations thereof.

3. The method of claim 1, wherein the sufficient amount of energy applied to the electrodes is varied by time phasing of input current or voltage to change energy distribution between the electrodes in the boreholes and thereby controlling the fracturing pattern in the formation.

4. The method of claim 1, wherein the sufficient amount of energy ranges from 1 kV to 2 MV at a frequency range of DC to 100 MHz for any of continuous waveforms and pulsed waveforms.

5. The method of claim 1 after applying a sufficient amount of energy to each pair of electrodes, further comprising:

measuring volumetric and channel electrical resistance between at least the pair of electrodes of the formation.

6. The method of claim 5, wherein

the measurement of volumetric electrical resistance is by network analyzer and the measurement of channel electrical resistance is by impedance spectroscopy;

and

wherein the electrical impulses are applied after the impedance spectroscopy and network analyzers measurements to indicate sufficient reduction of electrical impedance indicating presence of a conductive channel.

7. The method of claim 1, wherein at least one electrode is contained within a borehole wall, and wherein the at least one electrode is in contact with borehole wall through a spring loaded pin.

8. The method of claim 1, wherein each electrode is contained within a borehole wall and at least one electrode extends into the formation through the borehole wall by telescopically.

9. The method of claim 1, wherein a resultant change in volume resistivity of the formation to be fractured is measured between a pair of boreholes by impedance spectroscopy method, with borehole to borehole network analyzer measurement made over a range of frequencies from 60 Hz to 10 MHz to provide Cole-Cole plots of complex dielectric constant to characterize frequencies.

10. The method of claim 1, wherein the plurality of electrodes are connected to at least a surface waveform generator, and wherein the generator generates a voltage waveform to provide shock waves causing multiple fractures between the electrodes.

15. The method of claim 1, wherein the boreholes are any of vertical boreholes, horizontal boreholes, and combinations thereof to establish required volume of fracture.

16. The method of claim 1, wherein each borehole is provided with at least one electrode.

17. The method of claim 1, where each borehole is provided with a plurality of electrodes, with the plurality of electrodes being placed at different depths in the borehole.

18. The method of claim 1, wherein the plurality of electrodes are connected to at least a surface waveform generator for generating a time sequence of waveforms to generate electric shock wave excitations in the mineral and organic materials in the formation, generating fracture volume in the formation.

19. The method of claim 1, wherein at least one of the electrodes further comprises a plurality of secondary electrodes.

20. The method of claim 19, wherein the plurality of secondary electrodes are in contact with the formation.

21. The method of claim 19, further comprising injecting an easily ionizable gas in the boreholes.

22. The method of claim 19, wherein each secondary electrode is insulated from an adjacent secondary electrode.

23. The method of claim 19, wherein the plurality of secondary electrodes are placed in casing or open-hole in the boreholes to maximize radial electric field intensity initializing voltage discharge between the plurality of secondary electrodes and the formation.

24. The method of claim 1, wherein at least two electrodes are employed in each borehole.

25. The method of claim 1, further comprising using a borehole radar to gather information about the multiple fractures generated in the formation.

26. The method of claim 25, wherein the borehole radar is used to gather information relating to any of distribution, size of fracture and propagation velocity of the multiple fractures generated in the formation.

27. The method of claim 25, wherein the information about the multiple fractures includes any of location, orientation, and lateral extent of fracture zones intersecting the boreholes.

28. The method of claim 1, wherein placing the plurality of electrodes in the boreholes comprises positioning the electrodes in the boreholes for forming electrode configurations selected from two-wire transmission line, four-wire transmission line, cage-like transmission line structure, antennas, and combinations thereof.

30. The method of claim 1, wherein the formation is any of tight gas, shale gas, tight oil, tight carbonate, diatomite, geothermal, coalbed methane, methane hydrate containing formation, mineral containing formation, metal containing formation, a bedrock formation having a permeability in the range of 0.01 microdarcy to 10 millidarcy.

31. The method of claim 30, wherein the formation contains gas, and wherein the multiple fractures allows pressure in the formation to force recovery of gas contained within the formation.

32. The method of claim 30, wherein the formation is a diatomite formation, and further comprising:

injecting any of steam and water into the formation and through the multiple fractures; and

recovering hydrocarbons from the formation.

33. The method of claim 30, wherein the formation is any of a tight gas, a shale gas, or a coalbed methane formation, and further comprising:

injecting a liquid stream into the formation and the multiple fractures; and

recovering hydrocarbons from the formation.

34. The method of claim 30, wherein the formation is a coalbed methane formation, further comprising:

pumping water out of the formation through the multiple fractures; and

recovering methane gas from the formation.

35. The method of claim 30, wherein the formation is a geothermal formation, and further comprising:

recovering any of steam, heated water, and combinations thereof from the formation through the multiple fractures.

36. The method of claim 34, further comprising:

injecting any of water and steam into the formation into through the multiple fractures for the water to be heated by the geothermal formation.

11. The method of claim 11, wherein the voltage waveform has a frequency spectrum coinciding with a Cole-Cole plots for complex dielectric constant and Smith Chart plots for complex impedance.

12. The method of claim 11, wherein the voltage waveform has a frequency spectrum coinciding with a frequency range of lowest formation resistivity and maximum shock wave effect for fracture.

13. The method of claim 11, wherein the voltage waveform exceeds 100 kilovolts in amplitude with a corresponding current exceeding 1000 amperes in magnitude at peak value of a generator output waveform.

14. The method of claim 11, wherein the waveform generator is characterized by having a voltage and a current with a plurality of shapes selected from pulse, damped sine wave, and exponential decay.

29. A method of generating fractures in a formation containing connate water, the method comprising:

providing a plurality of boreholes in the formation;

placing a plurality of electrodes in the boreholes with one electrode per borehole, with the plurality of electrodes defining a fracture pattern for the geologic formation;

applying a sufficient amount of energy to the electrodes to heat the connate water in the formation to any of subcritical condition or supercritical condition; and

applying electrical impulses having a voltage output ranging from 100-2000 kV, an energy output of 10-1000 kJ, wherein the pulses have a rise time ranging from 0.05-500 microseconds and a half-value time of 50-5000 microseconds;

wherein the application of the electrical pulses generates allow plasma shock waves in the water creating multiple fractures in the formation.