Method for calculating spatial and temporal distribution of the Gutenberg-Richter parameter for induced subsurface seismic events and its application to evaluation of subsurface formations
A method for evaluating fractures induced in subsurface formations includes determining hypocenters and origin times of induced seismic events from seismic signals detected by seismic sensors deployed above a volume of the subsurface formations to be evaluated and recording the detected signals for a selected time. A modified Gutenberg-Richter exponent is determined for each induced seismic event having at least a selected number of other induced seismic events within a selected radial distance thereof. A spatial distribution of the modified Gutenberg-Richter exponents is used to determine at least one property of the induced fractures.
1. A method for evaluating fractures induced in subsurface formations, comprising:
determining hypocenters and origin times of induced seismic events from seismic signals detected by seismic sensors deployed above a volume of the subsurface formations to be evaluated and recording the detected signals for a selected time;
determining, using a computer, a modified Gutenberg-Richter exponent for each induced seismic event having at least a selected number of other induced seismic events within a selected radial distance thereof;
using a spatial distribution of the modified Gutenberg-Richter exponents to determine at least one property of the induced fractures.
2. The method of claim 1 wherein the at least one property comprises identification of whether an induced seismic event is caused by reactivation of an existing fault or creation of a new fault.
3. The method of claim 1 wherein the at least one property comprises identification of whether an induced seismic event is a result of a tectonic fault or an induced fault.
4. The method of claim 1 wherein determining the modified Gutenberg-Richter exponent for each induced seismic event comprises:
identifying a smallest magnitude one of the induced seismic events;
calculating an arithmetic mean of magnitudes of all induced seismic events within the selected radial distance; and
using the smallest magnitude and arithmetic mean to determine the modified Gutenberg-Richter exponent.
5. The method of claim 1 wherein determining the modified Gutenberg-Richter exponent for each induced seismic event comprises:
identifying a smallest magnitude one of the induced seismic events;
calculating an arithmetic mean of magnitudes of all induced seismic events within the selected radial distance and closest in time of occurrence to the induced seismic event being evaluated; and
using the smallest magnitude and arithmetic mean to determine the modified Gutenberg-Richter exponent.
6. The method of claim 1 wherein the induced seismic events are generated by pumping a fracture treatment into a wellbore drilled through selected subsurface formations.
7. A computer readable medium having stored thereon a computer program, the program having logic operable to cause programmable computer to perform a method for evaluating fractures induced in subsurface formations, the method including steps comprising:
determining hypocenters and origin times of induced seismic events from seismic signals detected by seismic sensors deployed above a volume of the subsurface formations to be evaluated and recording the detected signals for a selected time;
determining a modified Gutenberg-Richter exponent for each induced seismic event having at least a selected number of other induced seismic events within a selected radial distance thereof;
using a spatial distribution of the modified Gutenberg-Richter exponents to determine at least one property of the induced fractures.
8. The computer readable medium of claim 7 wherein the at least one property comprises identification of whether an induced seismic event is caused by reactivation of an existing fault or creation of a new fault.
9. The computer readable medium of claim 7 wherein the at least one property comprises identification of whether an induced seismic event is a result of a tectonic fault or an induced fault.
10. The computer readable medium of claim 7 wherein determining the modified Gutenberg-Richter exponent for each induced seismic event comprises:
identifying a smallest magnitude one of the induced seismic events;
calculating an arithmetic mean of magnitudes of all induced seismic events within the selected radial distance; and
using the smallest magnitude and arithmetic mean to determine the modified Gutenberg-Richter exponent.
11. The computer readable medium of claim 7 wherein the determining he modified Gutenberg-Richter exponent for each induced seismic event comprises:
identifying a smallest magnitude one of the induced seismic events;
calculating an arithmetic mean of magnitudes of all induced seismic events within the selected radial distance and closest in time of occurrence to the induced seismic event being evaluated; and
using the smallest magnitude and arithmetic mean to determine the modified Gutenberg-Richter exponent.
12. The computer readable medium of claim 7 wherein the induced seismic events are generated by pumping a fracture treatment into a wellbore drilled through selected subsurface formations.