Device and method for calculating 3D angle gathers from reverse time migration

A non-transitory computer readable medium including computer executable instructions, wherein the instructions, when executed, implement a method for calculating angle domain common image gathers (ADCIGs) for use in generating a final image of a subsurface of the earth, the method comprising:

• calculating with wavefield forward propagation, in a time-space domain, a source wavefield pF of a seismic source;
• calculating with wavefield back propagation, in the time-space domain, a receiver wavefield pB of a seismic receiver configured to detect a seismic wave generated by the seismic source, wherein the seismic wave emitted by the seismic source enters the subsurface of the earth and gets reflected on a reflector of the subsurface prior to arriving at the seismic receiver;
• applying an algorithm of anti-leakage Fourier transform (ALFT) to transform the source wavefield pF to a wavenumber domain;
• applying the ALFT algorithm to the receiver wavefield to transform the receiver wavefield in the wavenumber domain;
• determining an imaging condition to the ALFT source and receiver wavefields in the wavenumber domain;
• computing a reflection angle θ and an azimuth angle φ of the source wavefield pF and receiver wavefield pB in the wavenumber domain;
• calculating the ADCIGs in the wavenumber domain;
• and
• applying an inverse fast Fourier transform (FFT) to determine the ADCIGs in the space domain.

A processing device configured to calculate angle domain common image gathers (ADCIGs) for use in generating a final image of a subsurface of the earth, the processing device comprising:

• an interface configured to receive seismic data;
• and
• a processor connected to the interface and configured to,
• calculate with wavefield forward propagation, in a time-space domain, a source wavefield pF of a seismic source,
• calculate with wavefield back propagation, in the time-space domain, a receiver wavefield pB of a seismic receiver configured to detect a seismic wave generated by the seismic source, wherein the seismic wave emitted by the seismic source enters the subsurface of the earth and gets reflected on a reflector of the subsurface prior to arriving at the seismic receiver,
• apply an algorithm of anti-leakage Fourier transform (ALFT) to transform the source wavefield pF to a wavenumber domain,
• apply the ALFT algorithm to the receiver wavefield to transform the receiver wavefield in the wavenumber domain,
• determine an imaging condition to the ALFT source and receiver wavefields in the wavenumber domain,
• compute a reflection angle θ and an azimuth angle φ of the source wavefield pF and receiver wavefield pB in the wavenumber domain,
• calculate the ADCIGs in the wavenumber domain, and
• apply an inverse fast Fourier transform (FFT) to determine the ADCIGs in the space domain.