Electrically conductive proppant coating and related methods
An electrically conductive proppant coating and a method for applying the coating to the proppant, whereby the coated electrically conductive proppant can determine formation characteristics, such as dimensions, orientation, and conductivity.
1. A method for determining geometry of a fracture in a subterranean formation, the method comprising:
a. injecting a coated proppant into the fracture to cause the fracture to function as an emitting antenna while opening the fracture or holding the fracture open, the coated proppant including a proppant suspended in an electrically-conductive coating, the electrically-conductive coating (i) deposited on a proppant surface of the proppant, (ii) stabilized with an oxidizing agent, and (iii) including a mixture of carbon residue forming material and a solvent, the coated proppant carbonized and graphitized, the carbon residue forming material being petroleum pitch, the solvent being toluene, xylene, quinoline, tetrahydrofuran, tetralin, or naphthalene;
b. sending, via electrical connections, a time-varying electrical signal into the fracture to charge the coated proppant, the time-varying electrical signal generated at a top surface above the fracture;
c. detecting, via a plurality of surface antennas at the top surface, the time-varying electrical signal, the plurality of surface antennas spaced from each other over an area above the fracture; and
d. determining the geometry of the fracture based on the time-varying electrical signal detected by the plurality of surface antennas.
2. The method according to claim 1 , wherein the solvent is toluene.
3. The method according to claim 1 , wherein the solvent is xylene.
4. The method according to claim 1 , wherein the electrically-conductive coating is graphitized immediately after being carbonized.
5. The method according to claim 1 , wherein the electrical connections extend from the surface of the fracture to a well casing.
6. The method according to claim 1 , wherein the electrical connections extend to a mud pit.
7. The method according to claim 1 , wherein the time-varying electrical signal is generated via a reversing DC current.
8. The method according to claim 1 , wherein the time-varying electrical signal is generated via an AC current.
9. The method according to claim 1 , wherein the detecting the time-varying electrical signal includes recording the time-varying electrical signal.
10. The method according to claim 1 , wherein the plurality of surface antennas are spaced from each other over different parts of the fracture.
11. The method according to claim 1 , wherein the oxidizing agent is a gaseous oxidizing agent.
12. The method according to claim 11 , wherein the gaseous oxidizing agent is selected from a group consisting of oxygen, sulfur fumes, gaseous oxides, nitrogen oxide gas, ambient air, halogens or combinations thereof.
13. A method for determining geometry of a fracture in a subterranean formation, the method comprising:
a. injecting a coated proppant into the fracture, the coated proppant including a proppant suspended in an electrically-conductive coating material deposited on a surface of the proppant and stabilized with an oxidizing agent, the coated proppant carbonized and graphitized;
b. sending a time-varying electrical signal into the fracture to charge the coated proppant;
c. detecting, via a plurality of surface antennas, the time-varying electrical signal, the plurality of surface antennas spaced from each other over an area above the fracture; and
d. determining the geometry of the fracture based on the time-varying electrical signal detected by the plurality of surface antennas.
14. The method according to claim 13 , wherein the coating material includes a mixture of carbon residue forming material and a solvent or combination of solvents.
15. The method according to claim 14 , wherein the carbon residue forming material is petroleum pitch.
16. The method according to claim 14 , wherein the solvent or combination of solvents is selected from a group consisting of toluene, xylene, quinoline, tetrahydrofuran, tetralin, naphthalene or combinations thereof.
17. The method according to claim 13 , wherein the coated proppant is injected into the fracture during creation of the fracture.
18. The method according to claim 13 , wherein the plurality of surface antennas are spaced from each other over different parts of the fracture.