Determining orientation of vertical fractures with well logging tools
AssigneeExxon Production Research Company
InventorsChih-Ping J. Lu, Long D. Pham, Sen-Tsuen Chen
Life of this patent
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Abstract
The orientation of vertical fractures in subsurface rock formations is determined. A cross-dipole logging tool collects four-component shear-wave seismic data through a formation interval of interest in a subsurface formation adjacent a well bore. A gyroscope is typically provided to indicate compass orientation of the logging tool. The collected seismic data are then transformed within a time window containing arrivals of the shear waves to a new coordinate system within which the motion of the shear waves becomes linear. In the new coordinate system, the shear wave data are processed to determine the presence and orientation of fractures in the formation.
Claims20
A method of obtaining a measure of vertical fractures in subsurface formations adjacent well boreholes, comprising the steps of:
- positioning a logging tool at a depth of interest in the well borehole with two orthogonal shear wave seismic sources and two pairs of shear wave receivers, one receiver of each pair being axially aligned with one of the seismic sources;
- sending shear wave energy into the formation from the seismic sources;
- receiving shear wave energy at each receiver in the pairs of receivers;
- transforming the received shear wave energy into planes in which the wave motion is linear;
- and
- resolving the shear waves into component waves of different velocities, caused by polarization of the shear wave energy, in the planes of linear wave motion to indicate possible formation fractures.
A method of obtaining a measure of vertical fractures in subsurface formations adjacent a well logging tool in a well borehole, comprising the steps of:
- sending shear wave seismic energy from the logging tool into the subsurface formation in orthogonal planes;
- receiving the shear wave seismic energy at a pair of seismic receivers;
- transforming the received shear wave seismic energy into faster and slower shear wave components caused by polarization of the shear wave energy in the formation;
- and
- determining the time delay between the faster and slower shear wave components to indicate the presence of vertical fractures in the subsurface formation.
Dependencies are inferred from the claim text.