Shear wave source for VSP and surface seismic exploration
AssigneeHalliburton Energy Services, Inc.
InventorMark E. Willis
Life of this patent
Estimating the term…
Abstract
Seismic shear-wave survey systems and methods that employ inclined borehole pairs with directional detonations. If the boreholes have substantially equal inclinations in opposite azimuthal directions, the resulting signal traces can be combined to isolate shear wave energy contributions, thereby offering potentially enhanced resolution and reduced-complexity interpretation. The boreholes may be cased to ensure repeatability for, e.g., monitoring of reservoir fracturing, treatments, and/or drainage. The directional charges may be immersed to improve coupling of seismic energy into the formation.
Claims25
A method of surveying with seismic shear waves, the method comprising:
- generating the seismic shear waves with directional detonations detonated separately but at approximately a same time, the directional detonations in a pair of inclined boreholes that cross from a side profile but do not intersect and have similar inclination angles of approximately 45° from vertical in opposite azimuthal directions;
- acquiring signals representative of a receiver array's response to each of the pair of directional detonations;
- subtracting the response signals to suppress compressional wave information and enhance shear wave information;
- and
- displaying a subsurface log or image derived from the subtracted responses, wherein the acquired signals reflect a diffraction or scattering of the generated seismic shear waves as they pass through a fluid-filled fracture in a formation being surveyed.
A shear wave surveying system that comprises:
- a pair of inclined boreholes that cross from a side profile but do not intersect and have similar inclination angles of approximately 45° from vertical in opposite azimuthal directions;
- a receiver array that provides data in the form of one or more sets of seismic traces in response to shear waves generated by directional detonations detonated separately but at approximately a same time in each of said boreholes;
- a recording system that records each set of seismic traces;
- and
- a processing system that subtracts the sets to extract enhanced shear-wave information and provide a subsurface log or image of subsurface formation structures, wherein the enhanced shear-wave information reflects a diffraction or scattering of the generated shear waves as they pass through a fluid-filled fracture in a formation being surveyed.
Dependencies are inferred from the claim text.