Process and apparatus for coupled electromagnetic and acoustic stimulation of crude oil reservoirs using pulsed power electrohydraulic and electromagnetic discharge

• US 6,227,293 B1
• Filed: 02/09/2000
• Issued: 05/08/2001
• Est. Priority Date: 02/09/2000
• Status: Expired due to Fees

• Current Assignee: Conoco Incorporated (ConocoPhillips)
• Original Assignee: Conoco Incorporated (ConocoPhillips)
• Inventors: Wesley, Richard H., Huffman, Alan Royce
• Primary Examiner(s): Bagnell, David
• Assistant Examiner(s): Dougherty, Jennifer R.
• Application Number:
  US09/500,669
• Time in Patent Office: 454 Days
• Field of Search: 166/248, 166/249, 166/370, 166/177.1, 166/177.2, 166/177.6, 166/177.7
• US Class Current: 166/248
• 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 43/003 Vibrating earth formations

Abstract

Pulsed power sources are installed in one or more wells in the reservoir interval. The pulse sources include (1) an electrohydraulic generator that produces an intense and short lived electromagnetic pulse that travels at the speed of light through the reservoir, and an acoustic pulse from the plasma vaporization of water placed around the source that propagates through the reservoir at the speed of sound in the reservoir and (2) an electromagnetic generator that produces only an intense and short lived electromagnetic pulse that travels at the speed of light through the reservoir. The electromagnetic pulse produces a high frequency vibration of the reservoir that is active at the scale of the pores in the rock that acts to decrease the effective viscosity of the oil and lower the resistance of the crude oil to flow, and the acoustic pulse from the plasma effect enhances the mobility of the crude further. The combination of electrohydraulic and electromagnetic generators in the reservoir causes both the acoustic vibration and electromagnetically-induced high-frequency vibrations occur over an area of the reservoir where stimulation is desired. Single generators and various configurations of multiple electrohydraulic and electromagnetic generators stimulate a volume of reservoir and mobilize crude oil so that it begins moving toward a producing well. The method can be performed in a producing well or wells, an injector well or wells, or special wells drilled for the placement of the pulsed power EOR devices. The method can be applied with other EOR methods such as water flooding, CO2 flooding, surfactant flooding, diluent flooding in heavy oil reservoirs.

Claims

1. A method for recovering hydrocarbons from at least one porous zone of a subterranean formation, the method comprising:

(a) generating an electrical pulsed discharge in a first borehole at a distance from the at least one porous zone and propagating an electromagnetic wave into the formation at a first time, said electromagnetic wave reaching the at least one porous zone at a time substantially equal to the first time and inducing ultrasonic vibrations within said at least one porous zone;

(b) propagating at a second time an acoustic wave into the formation, said acoustic wave arriving at said at least one porous zone at a time substantially equal to the first time and combining with said ultrasonic vibrations thereby enhancing the mobility of previously immobile oil in the at least one porous zone; and

;

(c) producing the mobilized oil from a producing well in the at least one porous zone.

2. The method of claim 1 further comprising generating the acoustic wave in the first borehole.

3. The method of claim 2 wherein the acoustic wave is generated by an electrohydraulic discharge device contained within a sleeve of suitable material that allows propagation of the acoustic wave, but prevents interaction of a coupling fluid used in the generation of the acoustic wave with the fluids surrounding the electrohydraulic discharge device in the wellbore.

4. The method of claim 2 wherein the electromagnetic wave is produced by a first pulse generator and the acoustic wave is produced by a second pulse generator.

5. The method of claim 4 wherein the first and the second pulse generator each produce electromagnetic and acoustic pulses.

6. The method of claim 5 wherein the first and the second pulse generator are part of an array including a plurality of pulse generators, the method further comprising generating at least one additional electrical pulse for propagating at least one additional electromagnetic wave and acoustic wave, so that the second or later acoustic wave is permitted to reach a greater volume of the reservoir while the first or later electromagnetic wave is still causing induced acoustic vibration in the reservoir.

7. The method of claim 5 wherein the first and the second pulse generator are part of an array including a plurality of pulse generators, the method further comprising generating multiple electrical pulses at the same time, but with variable pulse durations and energies that permit the simultaneous stimulation of different scale dependent features with the reservoir.

8. The method of claim 7, further comprising generating at least one additional electrical pulse for propagating at least one additional electromagnetic wave and acoustic wave at a time substantially after the first discharge time, so that the first or later acoustic wave is permitted to reach a greater volume of the reservoir while the second or later electromagnetic wave is still causing induced acoustic vibration in the reservoir.

9. The method of claim 4 wherein the first and the second pulse generator are part of an array including a plurality of pulse generators, the method further comprising generating at least one additional electrical pulse for propagating at least one additional electromagnetic wave at a time after the first time, and propagating at least one additional acoustic wave, so that the first acoustic wave is permitted to reach a greater volume of the reservoir while the first or later electromagnetic wave is still causing induced acoustic vibration in the reservoir.

10. The method of claim 9 wherein the at least one porous zone comprises at least two spaced apart porous zones, the method further comprising activating the plurality of pulse generators at selected times, said times being selected for enabling an acoustic and an electromagnetic wave from different pulse generators to arrive at each of the at least two porous zones at substantially the same time.

11. The method of claim 4 wherein the said electromagnetic wave, generated from a pulse generator or generators in an array of pulse generators, that reaches the at least one porous zone causes a vibration that has a finite time duration such that the acoustic wave generated from the first pulse generator can pass a given location in the at least one porous zone while the ultrasonic vibration induced by the electromagnetic pulse is still active.

12. The method of claim 4 wherein the first and the second pulse generator are part of an array including a plurality of pulse generators, the method further comprising generating multiple electromagnetic waves at the same time, but with variable pulse durations and energies that permit the simultaneous stimulation of different scale dependent features with the reservoir by electromagnetically-induced acoustic vibration.

13. The method of claim 1 further comprising generating the acoustic wave in a second borehole different from the first borehole.

14. The method of claim 1 wherein a difference between the first time and the second time is selected based upon a velocity of propagation of the acoustic wave in the formation.

15. The method of claim 1 further comprising introducing a material selected from (i) steam, (ii) water, (iii) a surfactant, (iv) diluent, and, (v) CO₂ into the subterranean formation, said introduced material further enabling at least one of (A) increased mobility of the hydrocarbons, and, (B) increased flow of the hydrocarbons.

16. The method of claim 15 wherein introducing the introduced material into the formation further comprises injecting said material in an injection well.

17. The method of claim 1 wherein the said first electromagnetic wave that reaches the at least one porous zone causes a vibration that has a finite time duration such that the acoustic wave can pass a given location in the at least one porous zone while the electromagnetic vibration is still active.

18. The method of claim 1 wherein the electrical pulsed discharge generates the electromagnetic wave using a magnetic pulse generator that discharges electricity into a single- or multiple-turn coil, thus producing an electromagnetic wave, but produces no direct acoustic wave.

19. The method of claim 1 wherein the pulsed electric discharge is initiated using a filament of flexible conductive material that extends across a gap between a pair of electrodes and reduces wear on the electrodes during discharge, said filament being replaced after each discharge through an automated spooling feed device that feeds new filament into the discharge gap through a hole in one of the electrodes.

20. The method of claim 1 wherein the pulsed electric discharge is initiated using a pencil-shaped filament of rigid conductive material that extends across a gap between a pair of electrodes and reduces wear on the electrodes during discharge, said filament being replaced after each discharge through an automated feed device that feeds new filament into the discharge gap through a hole in one of the electrodes.

21. The method of claim 1 wherein the pulsed electric discharge is initiated using a jet of combustible gas that extends across a gap between a pair of electrodes and reduces wear on the electrodes during discharge, said gas being applied under pressure through a hole in one of the electrodes.

22. The method of claim 1 wherein the electrical pulsed discharge is produced by an electrical pulsed discharge device contained within a packer assembly, said packer assembly being designed to isolate the discharge device from the rest of the wellbore, and with inflow and outflow fluid lines so as to provide re-circulation of fluids around the discharge device in the packed off interval, and to apply and maintain positive fluid pressure to improve the coupling of the acoustic wave to the wellbore.

23. The method of claim 1 wherein the electrical pulsed discharge is generated using a reflecting cone that allows the acoustic wave to be directed at a given azimuth or range of azimuths, said reflecting cone also being designed to focus the acoustic energy at a given inclination from the wellbore and also being controlled such that the energy can be redirected to different azimuths from time to time during operation by repositioning of the reflecting cone through a remote control.

24. The method of claim 1, the method further comprising controlling the pulse characteristics of the electromagnetic wave so that an acoustic vibration induced by the electromagnetic wave in the reservoir produces vibration frequencies that are optimized to enhance stimulation at a given scale of inclusion in the reservoir including (i) the pore scale, (ii) the grain scale, (iii) the flat crack scale, (iv) the fracture scale, (v) the lamina scale, (vi) the bedding scale, (vii) the reservoir body length scale, or (ix) any other scale appropriate for stimulation of oil production.

25. A system for improving the recovery of crude oil from at least one porous zone of a subterranean formation, the system comprising:

(a) at least one source within a borehole in the subterranean formation for generating an electromagnetic (EM) pulse at a first time, said EM pulse propagating into the formation and reaching said at least one porous zone at a time substantially equal to the first time and thereby inducing ultrasonic vibrations therein;

(b) at least one source for transmitting an acoustic pulse into the formation, said acoustic pulse having a velocity of propagation in the formation and arriving at said porous zone at a time substantially equal to the first time; and

(c) a timing and synchronization device for activating said at least one acoustic source at a time that is a function of the first time, said velocity of propagation and a distance from said at least one acoustic source to said porous zone.

26. The system of claim 25 wherein the at least one EM source and the at least one acoustic source are located in a single borehole in the subsurface.

27. The system of claim 26 wherein the at least one EM source and the at least one acoustic source are part of an electrohydraulic device.

28. The system of claim 27 wherein the electrohydraulic device further comprises a sleeve for isolating the interior of the electrohydraulic device from fluids surrounding the electrohydraulic device in the wellbore.

29. The system of claim 26 wherein said at least one EM source and said at least one acoustic source are part of an array including a plurality of pulse generators.

30. The system of claim 29 further comprising a controller for generating multiple electrical pulses at the same time with variable pulse durations and energies for simultaneous stimulation of different scale-dependent features of the subterranean formation.

31. The system of claim 25 wherein the at least one EM source and the at least one acoustic source are located in different boreholes in the subsurface.

32. The system of claim 25 further comprising a device for introducing at least one of (i) steam, (ii) water, (iii) a surfactant, (iv) a diluent, and, (v) CO₂ into the subterranean formation.

33. The system of claim 25 wherein the at least one EM source further comprises a magnetic pulse generator that discharges electricity into a single or multiple-turn coil, thus producing an EM wave but no direct acoustic wave.

34. The system of claim 25 wherein the at least one EM source further comprises

(i) a filament of flexible conductive material extending across a discharge gap between two electrodes, and

(ii) a spooling device for feeding new filament into the discharge gap through a hole in one of said electrodes.

35. The system of claim 25 wherein the at least one EM source further comprises a pencil-shaped filament of rigid conductive material that extends across a discharge gap between two electrodes, said pencil shaped filament being replaced through a feed device that feeds new filament into the discharge gap through a hole in one of the electrodes.

36. The system of claim 25 wherein the at least one EM source further comprises:

(i) a pair of electrodes defining a discharge gap there between; and

(ii) a tube within one of said pair of electrodes for conveying combustible gas into said discharge gap.

37. The system of claim 25 wherein the at least one EM source and the acoustic source is contained within a packer assembly, said packer assembly designed to isolate said at least one source from the rest of the wellbore.

38. The system of claim 25 wherein the at least one acoustic source further comprises a reflecting cone for directing the acoustic pulse at a predetermined inclination to the wellbore.

39. The system of claim 38 wherein the at least one acoustic source further comprises a mechanism for orienting the reflecting cone at a predetermined azimuth.