Q tomography method
AssigneeExxonMobil Upstream Research Company
InventorWenyi Hu
Life of this patent
Estimating the term…
Abstract
Method for reconstructing subsurface Q models (110) from seismic data (10) by performing ray-based (60), centroid frequency shift (50) Q tomography. The seismic source waveform's amplitude spectrum is approximated by a frequency-weighted exponential function of frequency (40), having two parameters to adjust to fit the frequency shift data, thereby providing a better fit to various asymmetric source amplitude spectra. Box constraints may be used in the optimization routine, and a multi-index active-set method used in velocity tomography is a preferred technique for implementing the box constraints (100).
Claims20
A ray-based, centroid frequency shift Q tomography method for reconstructing a subsurface Q model from seismic data measured by receivers in a survey using a seismic source, comprising:
- selecting a mathematical function to approximate the seismic source's amplitude spectrum, and using this to calculate the spectrum's centroid frequency shift due to earth attenuation, and relating said centroid frequency shift to attenuation by a line integral along a ray path connecting the seismic source to a receiver, said attenuation being represented by the reciprocal of quality factor Q, and solving for Q or 1/Q by iterative, linear optimization using a computer, wherein the optimization has box constraints to keep estimated Q values between an upper limit and a lower limit, which limits may be constant or may vary with position.
A ray-based, centroid frequency shift Q tomography method for reconstructing a subsurface model for Q or 1/Q from seismic data measured by receivers in a survey using a seismic source, comprising:
- using a frequency-weighted exponential function of frequency to approximate the seismic source's amplitude spectrum in order to calculate the spectrum's centroid frequency shift due to earth attenuation, and relating said centroid frequency shift to attenuation by a line integral along a ray path connecting the seismic source to a receiver, said attenuation being represented by the reciprocal of quality factor Q, and solving for Q or 1/Q by iterative, linear optimization performed using a computer.
Dependencies are inferred from the claim text.