RESERVOIR CHARACTERIZATION FROM MULTICOMPONENT MICROSEISMIC DATA
A method for determining seismic anisotropy of subsurface rock formations includes measuring passive seismic signals at a plurality of locations above an area of the Earth's subsurface to be surveyed. The compressional- and shear-wave arrival times from at least one origin location of a seismic event occurring in the subsurface are determined from the measured seismic signals. The arrival times are inverted to obtain values of the seismic anisotropy parameters.
1 . A method for determining effective seismic anisotropy of subsurface rock formations, comprising:
measuring passive seismic signals at a plurality of locations above an area of the Earth's subsurface to be surveyed;
selecting, from the measured signals, shear wave arrival times and compressional wave arrival times from at least one origin location of a seismic event occurring in the subsurface;
inverting the shear wave and compressional wave arrival times to obtain values of seismic anisotropy parameters; and
at least one of storing and displaying the anisotropy parameters.
2 . The method of claim 1 further comprising determining a location of origin of at least one seismic event from the arrival times.
3 . The method of claim 1 further comprising repeating the measuring passive seismic signals, selecting arrival times, inverting the arrival times, and storing or displaying anisotropy parameters at at least one later time.
4 . The method of claim 1 further comprising inverting the compressional and shear arrival times for the anisotropy and using the anisotropy parameters to determine seismic migration velocities.
5 . The method of claim 1 further comprising using the anisotropy parameters to determine at least one of density of fractures in subsurface formations, orientation of fractures in the subsurface formations, maximum and minimum horizontal stresses in the subsurface formations and orientations thereof.
6 . A method for monitoring a formation fracturing procedure, comprising:
recording seismic signals at selected positions near the Earth's surface proximate a wellbore during pumping of fracturing fluid into the wellbore;
selecting, from the measured signals, shear wave arrival times and compressional wave arrival times from at least one origin location of a seismic event occurring in the subsurface;
inverting the shear wave and compressional wave arrival times to obtain values of seismic anisotropy parameters; and
determining a position of a fluid front from the inverted shear wave and compressional wave arrivals by determining a location of origin of at least one seismic event.
7 . The method of claim 6 further comprising repeating the inverting the shear wave and compressional wave arrival times and determining a position of a fluid front at at least one later time.
8 . The method of claim 7 further comprising determining at least one of density of fractures in subsurface formations, orientation of fractures in the subsurface formations, maximum and minimum horizontal stresses in the subsurface formations and orientations thereof from the repeated inverting shear wave and compressional wave arrival times and determining the fluid front location.