CONTINUOUS MICROSEISMIC MAPPING FOR REAL-TIME 3D EVENT DETECTION AND LOCATION

• US 20090259406A1
• Filed: 04/08/2009
• Published: 10/15/2009
• Est. Priority Date: 04/09/2008
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Leaney, W. Scott, Leslie, Harold David, Khadhraoui, Bassem, Michaud, Gwenola
• Granted Patent: US 8,494,777 B2
• Time in Patent Office: Days
• US Class Current: 702/14
• CPC Class Codes: G01V 1/288 Event detection in seismic signals, e.g. microseismics G01V1/36 takes precedence
• CPC Class Codes: G01V 1/40 specially adapted for well-logging
• CPC Class Codes: G01V 2210/123 Passive source, e.g. microseismics
• CPC Class Codes: G01V 2210/1429 Subsurface, e.g. in borehole or below weathering layer or mud line

Abstract

A method for the detection and localization of microseismic events is proposed which operates in real-time. It provides hypocenters in three spatial dimensions along with an estimate of the event origin time. Sensor positions may be distributed in 3D space, and are not confined to linear arrays in vertical wells. The method combines and improves two existing approaches. For detection and localization purposes the method makes use of the generalized beam-forming and forward modeling properties defined in the “CMM” algorithm. For location refinement, the method uses a stabilized version of the generalized “Geiger” approach.

Claims

1. A method of detecting and locating a microseismic event, comprising:

providing an estimate of a velocity model for a formation;

estimating a volume of space in which the event will most likely occur;

dividing the volume into a plurality of sub-volumes;

receiving data of a microseismic event with at least a first and a second seismic sensor located on a tool in a wellbore;

approximating a location of the event by coalescing a plurality of seismic signals received with the receivers at selected locations and time in the volume to determine in which sub-volume the event occurred; and

determining a more precise location of the event by locating the events within the sub-volume utilizing the signals.

2. A method of detecting and locating a microseismic event, comprising:

providing an estimate of a velocity model for a formation;

estimating a volume of space in which the event will most likely occur;

dividing the volume into a plurality of sub-volumes;

receiving data of a microseismic event with at least a first and a second seismic sensor located on a tool in a wellbore;

approximating a location of the even in the volume to determine in which sub-volume the event occurred; and

determining a more precise location of the event by locating the event within the sub-volume utilizing the signals.