Determining fracture length via resonance
View Patent ↗A system and method to determine a length of a fracture induced from a borehole are described. The method includes isolating a portion of the borehole, the portion of the borehole including an end of the fracture at the borehole wall, increasing fluid pressure in the portion of the borehole, deploying a low-frequency source in the portion of the borehole, and varying a frequency of the low-frequency source to generate resonance oscillations at a resonance frequency in the fracture. The method also includes determining the length of the fracture based on the resonance frequency.
1. A method of determining a length of a fracture induced from a borehole, the method comprising:
isolating a portion of the borehole, the portion of the borehole including an end of the fracture at the borehole wall;
increasing fluid pressure in the portion of the borehole;
deploying a low-frequency source in the portion of the borehole;
varying a frequency of the low-frequency source to generate resonance oscillations at a resonance frequency in the fracture; and
determining the length of the fracture based on the resonance frequency;
wherein the increasing fluid pressure is by movement of a piston within a pipe in the portion of the borehole.
2. The method according to claim 1 , wherein the isolating the portion of the borehole includes positioning packers above and below the portion of the borehole.
3. The method according to claim 1 , wherein the increasing fluid pressure causes the fracture to open and elongate.
4. The method according to claim 1 , wherein the increasing fluid pressure begins a cycle of fluid movement into and out of the fracture.
5. The method according to claim 1 , further comprising determining the resonance frequency as a function of parameters including the length of the fracture.
6. The method according to claim 5 , wherein the resonance frequency is theoretically determined as a function of volume of the portion of the borehole, transverse cross-section of the fracture, viscosity of the fluid, and the length of the fracture.
7. The method according to claim 6 , wherein the resonance frequency is measured, the volume of the portion of the borehole, the transverse cross-section of the fracture, and the viscosity of the fluid are known, and the length of the fracture is determined based on the function.
8. A system to determine a length of a fracture induced from a borehole, the system comprising:
packers disposed to isolate a portion of the borehole that includes an end of the fracture at the borehole wall;
a piston deployed in a pipe coupled to a packer, the piston movement increasing fluid pressure in the portion of the borehole;
a low-frequency source deployed in the portion of the borehole, the low-frequency source generating resonance oscillations at a resonance frequency in the fracture; and
a processor configured to determine the length of the fracture based on the resonance frequency.
9. The system according to claim 8 , wherein the piston increasing the fluid pressure causes the fracture to open and elongate.
10. The system according to claim 8 , wherein the piston movement corresponds with a cycle of fluid movement into and out of the fracture.
11. The system according to claim 8 , wherein the processor determines the resonance frequency as a function of parameters including the length of the fracture.
12. The system according to claim 11 , wherein the processor theoretically determines the resonance frequency as a function of volume of the portion of the borehole, transverse cross-section of the fracture, viscosity of the fluid, and the length of the fracture.
13. The system according to claim 12 , wherein the resonance frequency is measured, the volume of the portion of the borehole, the transverse cross-section of the fracture, and the viscosity of the fluid are known, and the processor determines the length of the fracture based on the function.