Method and apparatus for hydraulic fracture geometry evaluation

1. A method of hydraulic fracturing geometry evaluation, comprising:

injecting a fracturing fluid comprising a magnetic material into a subsurface fracture;

energizing the subsurface fracture by sequential activation of one or more electric current sources disposed at different subsurface positions, including at least one position in the subsurface fracture and other positions located at different distances from the subsurface fracture, wherein the sequential activation comprises activation according to a spatial sequence of the different subsurface positions;

measuring an electric field induced by the energizing of the subsurface fracture;

measuring a magnetic field generated by the magnetic material in the subsurface fracture; and

modeling, based on the measuring, a geometry of the fracture.

2. The method of claim 1 , further comprising monitoring the amount of magnetic material in the fracturing fluid during fracturing, and adjusting the amount of magnetic material based on the monitoring.

3. The method of claim 1 , further comprising injecting a conductive fluid into the fracturing fluid.

4. The method of claim 1 , wherein measuring at least one of (a) the magnetic field and (b) the electric field comprises measuring the field within a wellbore.

5. The method of claim 1 , wherein measuring at least one of (a) the magnetic field and (b) the electric field comprises measuring the field at the earth's surface.

6. The method of claim 1 , further comprising changing the rate at which the fracturing fluid is injected in the fracture based on the modeled geometry of the fracture.

7. The method of claim 1 , wherein the magnetic material comprises a powder.

8. An apparatus for hydraulic fracturing geometry evaluation, comprising:

at least one electric current source configured for energizing a subsurface fracture by sequential activation of each at least one electric current source, the at least one electric current source disposed at different subsurface positions, including at least one position in the subsurface fracture and other positions located at different distances from the subsurface fracture, wherein the sequential activation comprises activation according to a spatial sequence of the different subsurface positions;

means for providing measurement of an electric field induced by the energizing of the subsurface fracture;

means for providing measurement of a magnetic field generated by a magnetic material of a fracturing fluid, the fracturing fluid having been injected into the subsurface fracture; and

means for modeling, based on the measurements, a geometry of the fracture.

9. The apparatus of claim 8 , wherein the means for modeling calculates a length, a width and a depth of the subsurface fracture.

10. The apparatus of claim 8 , wherein the means for modeling calculates an optimal position of at least one of (a) the means for providing measurement of the electric field, and (b) the means for providing measurement of the magnetic field.

11. The apparatus of claim 8 , wherein the means for modeling calculates the sensitivity of at least one of (a) the electric field measurement and (b) the magnetic field measurement, at the different distances from the subsurface fracture.

12. The apparatus of claim 8 , wherein at least one of (a) the means for providing measurement of the electric field and (b) the means for providing measurement of the magnetic field detects the respective field at the different distances from the subsurface fracture.

13. An apparatus for hydraulic fracturing geometry evaluation, comprising:

at least one processor;

a memory coupled to the at least one processor, the memory comprising executable instructions that, when executed, cause the at least one processor to:

receive measurements of a magnetic field generated by a magnetic material of a fracturing fluid in a subsurface fracture;

receive measurements of an electric field induced by energizing the subsurface fracture by sequential activation of at least one electric current source disposed at different subsurface positions, including at least one position in the subsurface fracture and other positions located at different distances from the subsurface fracture, wherein the sequential activation comprises activation according to a spatial sequence of the different subsurface positions; and

model a geometry of the subsurface fracture based on the measurements.

14. The apparatus of claim 13 , wherein the at least one processor determines a length, a width and a depth of the subsurface fracture.

15. The apparatus of claim 13 , wherein the at least one processor determines optimal positions for one or more sensors, wherein the sensors are configured to receive measurements of the magnetic field generated by the magnetic material of the fracturing fluid or measurements of the electric field induced by energizing the subsurface fracture.

16. The apparatus of claim 13 , wherein the at least one processor determines the sensitivity of at least one of (a) the electric field measurements and (b) magnetic field measurements, at the different distances from the subsurface fracture.

17. The apparatus of claim 13 , further comprising one or more sensors that detect at least one of (a) the magnetic field and (b) the electric field.