Method and apparatus for analyzing fractures using AVOAz inversion
AssigneeCgg Services SAS
InventorJonathan Downton
Life of this patent
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Abstract
Fracture orientation ambiguity in the results of amplitude variation with offset and azimuth inversion is overcome by using additional geological information. Methods, apparatus and executable codes stored on non-transitory media cause, for each interface encountered by traces in a CMP gather, calculating angle-dependent azimuthal Fourier coefficients, performing a nonlinear inversion of amplitude versus offset and azimuth, AVOAz, equations built using the angle-dependent azimuthal Fourier coefficients to determine possible fracture orientations, and selecting one of the possible fracture orientations using constraints based on the additional geological information.
Claims20
A method for characterizing a fracture in an underground structure, the method comprising:
- receiving seismic data acquired during a seismic survey of the underground structure, and additional geological information;
- generating common midpoint, CMP, gathers of traces from the seismic data;
- for each interface encountered by traces in at least one of the CMP gathers:
- (i) estimating angle-dependent azimuthal Fourier coefficients, FCs,
- (ii) performing a nonlinear inversion of amplitude versus offset and azimuth angle, AVOAz, equations built using the angle-dependent azimuthal Fourier coefficients to determine possible fracture orientations, and
- (iii) selecting one of the possible fracture orientations using a stress constraint, a symmetric fracture constraint, a penny shape fracture constraint, an empirical constraint and/or a continuity constraint based on the additional geological information;
- and
- producing an image of the underground structure including the fracture with the selected one of the possible fracture orientations, the image being usable to design a hydrocarbon extraction plan.
A seismic data processing apparatus is configured to obtain an image of a fracture in an underground structure probed using seismic waves, the apparatus including:
- a user input interface configured to receive seismic data acquired during a seismic survey of the underground structure, and additional geological information;
- one or more processors configured to generate common midpoint, CMP, gathers of traces from the seismic data, and then, for each interface encountered by traces in at least one of the CMP gathers, the one or more processors being further configured to,
- (i) estimate angle-dependent azimuthal Fourier coefficients, FCs,
- (ii) perform a nonlinear inversion of amplitude versus offset and azimuth angle, AVOAz, equations built using the angle-dependent azimuthal FCs to determine possible fracture orientations, and
- (iii) select one of the possible fracture orientations using a stress constraint, a symmetric fracture constraint, a penny shape fracture constraint, an empirical constraint and/or a continuity constraint based on the additional information;
- and
- a display configured to display reflectivity in vertical slices of the underground structure, including the fracture with the selected one of the possible fracture orientations, these vertical slices being usable to design a hydrocarbon extraction plan.
A non-transitory computer-readable recording medium storing executable codes which, when executed by a computer, make the computer perform a method for characterizing a fracture in an underground structure, the method comprising:
- receiving seismic data acquired during a seismic survey of the underground structure, and additional geological information;
- generating common midpoint, CMP, gathers of traces from the seismic data;
- for each interface encountered by traces in at least one of the CMP gathers:
- (i) estimating angle-dependent azimuthal Fourier coefficients, FCs,
- (ii) performing a nonlinear inversion of amplitude versus offset and azimuth angle, AVOAz, equations built using the angle-dependent azimuthal Fourier coefficients to determine possible fracture orientations, and
- (iii) selecting one of the possible fracture orientations using a stress constraint, a symmetric fracture constraint, a penny shape fracture constraint, an empirical constraint or a continuity constraint based on the additional information;
- and
- producing an image of the underground structure including the fracture with the selected one of the possible fracture orientations, the image being usable to design a hydrocarbon extraction plan.
Dependencies are inferred from the claim text.