MICROSEISMIC FRACTURE MAPPING USING SEISMIC SOURCE TIMING MEASUREMENTS FOR VELOCITY CALIBRATION

1 - 10 . (canceled)

11 . A method for calibrating microseismic velocity, comprising the acts of:

transmitting a first signal through a wireline to trigger a seismic source;

detecting the first signal;

identifying a first time value associated with the first signal;

detecting an event associated with the seismic source;

transmitting a second signal from a first receiver unit to an analyzer, the second signal associated with the seismic source event; and

calibrating a microseismic velocity based on the time difference between the first time value and a second time value associated with the second signal.

12 . The method of claim 11 , further comprising the act of:

transmitting a third signal from a second receiver unit to the analyzer, the third signal also associated with the seismic source event.

13 . The method of claim 11 , wherein the act of transmitting a first signal comprises transmitting an electric current through the wireline, and wherein the act of the detecting the first signal comprises detects a change in the electric current in the wireline.

14 . The method of claim 11 , further comprising the act of filtering the first signal; and

wherein the act of identifying the first time value comprises generating a high-amplitude timing pulse associated with the first signal.

15 . The method of claim 11 , wherein the act of calibrating a microseismic velocity further comprises performing a ray-tracing inversion associated with the seismic source event.

16 . The method of claim 15 further comprising the act of applying a general forward model to the ray-tracing inversion.

17 . The method of claim 11 , further comprising the act of conducting a grid search to determine a velocity structure of the event.

18 . A computer readable medium containing executable instructions, which, when executed in a processing system, cause said processing system to perform operations comprising:

transmitting an electric current through a wireline to trigger a seismic source;

receiving an indicator of a change in the electric current to the first wireline;

identifying a first time value by generating a high-amplitude timing pulse associated with the signal;

transmitting the first time value;

receiving a second signal associated with the event; and

calibrating a microseismic velocity based on the time difference between the first time value and a second time value associated with the second signal.

19 . A computer readable medium containing executable instructions, which, when executed in a processing system, cause said processing system to perform operations comprising:

calculating an angle associated with a microseismic event;

estimating a velocity of a wave associated with the microseismic event;

receiving perforation arrival-time data associated with the microseismic event;

updating the estimated velocity using the perforation arrival-time data;

re-calculating the angle using the updated estimated velocity; and

calculating the velocity using the re-calculated angle.

20 . A method of monitoring microseismic events, comprising the acts of:

transmitting a first signal through a wireline to actuate a seismic source;

identifying a time value associated with the first signal;

detecting a microseismic event resulting from actuation of the seismic source;

determining a time difference between the transmitting of the first signal and the detecting of the microseismic event; and

determining a formation velocity in reference to the determine time difference.

21 . The method of claim 20 , wherein the act of identifying a time value associated with the first signal comprises communicating information to an analyzer which establishes a time reference for the first signal.

22 . The method of claim 21 , further comprising the act of communicating information associated with the detecting of the microseismic event to the analyzer, and wherein the determining of a time difference between the transmitting of the first signal and the detecting of the microseismic event is performed by the analyzer.

23 . The method of claim 20 , wherein the seismic source comprises a perforating gun.

24 . The method of claim 20 , wherein the act of detecting a microseismic event resulting from actuation of the seismic source comprises using a plurality of receivers to detect the microseismic event.

25 . A method of determining a formation velocity, comprising the acts of:

transmitting a trigger signal through a wireline to actuate a seismic source, the seismic source located in a first well;

generating a reference signal identifying the time of transmission of the trigger signal;

using a first receiver to detect a microseismic event resulting from actuation of the seismic source and to generate a receiver signal indicative of the microseismic event, the first receiver located in a second well;

determining a time difference between the transmitting of the trigger signal and the detecting of the first microseismic event resulting from the seismic source through reference to the reference signal and the receiver signal; and

evaluating the formation velocity of the formation between the first and second wells in reference to the determined time difference.

26 . The method of claim 25 , further comprising the acts of:

communicating the reference signal to an analyzer; and

communicating the receiver signal to the analyzer; and

wherein the act of determining a time difference is performed by the analyzer.

27 . The method of claim 26 , wherein the steps of communicating the reference signal and the receiver signal to the analyzer are each performed essentially as the signals are generated.

28 . The method of claim 25 , further comprising the acts of:

using a plurality of receivers to detect the microseismic event, and

determining the average velocity between the seismic source and at least a portion of the plurality of receivers.