Method for monitoring seismic events

• US 20050190649A1
• Filed: 12/22/2004
• Published: 09/01/2005
• Est. Priority Date: 12/29/2003
• Status: Abandoned Application

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: A Delaware Limited Liability Company, WesternGeco LLC (Schlumberger NV)
• Inventors: Primiero, Paolo, Eisner, Leo
• Application Number:
  US11/019,401
• Publication Number:
  US 20050190649A1
• Time in Patent Office: Days
• US Class Current: 367/38
• CPC Class Codes: G01V 1/40 specially adapted for well-logging
• CPC Class Codes: G01V 2210/123 Passive source, e.g. microseismics

Abstract

A microseismic method of monitoring fracturing operation or other passive seismic events in hydrocarbon wells is described using the steps of obtaining multi-component signal recordings from locations in the vicinity of a facture; and performing a waveform inversion to determine parameters representing a source characteristics of the event.

Claims

1. A method of passively monitoring a subterranean location comprising the steps of obtaining multi-component signals of a microseismic event within the location;

and performing a waveform inversion to determine parameters representing source characteristics of said microseismic event.

2. The method of claim 1 wherein the signal recordings are at least for the purpose of determining the source characteristics low-pass filtered or bandlimited to a frequency range within 0 to 100 Hz.

3. The method of claim 1 wherein the microseismic event is caused by a fracturing operation in a wellbore.

4. The method of claim 1 including the step of evaluating a Green'"'"'s function to derive the source characteristics from the obtained signals.

5. The method of claim 1 wherein the obtained signals are processed to identify P-wave or S-wave events prior to the wavefield inversion.

6. The method of claim 1 wherein the parameters of the source characteristics are represented by a moment tensor and/or source location and/or origin time.

7. The method of claim 1 further comprising the step of using single value decomposition to stabilize the waveform inversion.

8. The method of claim 1 including the step of minimizing the difference between obtained signals and synthetic signals.

9. The method of claim 1 including the step of minimizing the difference between obtained signals and synthetic signals with the synthetic signals depending on the estimated source characteristics.

10. The method of claim 9 wherein the step of minimizing the difference between obtained signals and synthetic signals includes a search over source locations and origin times for an estimated source characteristics.

11. The method of claim 9 wherein the step of minimizing the difference between obtained signals and synthetic signals includes a grid search over source locations, origin times for an estimated source characteristics.

13. The method of claim 1 wherein a source time function of the fracture is approximated by a delta function.

12. The method of claim 12 further comprising the steps of

estimating the initial origin time at possible source locations;

carrying out a search around the estimated origin time for each source location;

for said origin times finding the unique solution of a moment tensor of the source;

evaluating the least-square misfit between the recorded signals and synthetic signals derived by calculating the signals caused by a source of said moment tensor at the receiver locations; and

storing the best fitted solution for each source location.