Amplitude-preserved wave-equation migration Paul Sava & Biondo Biondi SEP108 (pages 1-27)
Wave-equation imaging Why? –Complex wavefields –Sharp velocity variation sub-salt What? –Reflectivity function of incidence angle Imaging Migration Velocity Analysis (MVA) Amplitude vs. Angle Analysis (AVA)
Angle-Domain Common Image Gathers Applications –imaging –S/G migration (Prucha et at., 1999) –shot-profile migration (Rickett, 2001) –seismic inversion (Prucha et. al., 2001) –MVA –traveltime tomography (Clapp, 2000) –wave-equation MVA (Sava & Biondi, 2000) –C-waves –polarity reversal (Rosales, 2001) –AVA –wave-equation AVA (Gratwick, 2001)
Angle-gathers vs. offset-gathers Offset gather Angle gather
Agenda ADCIG kinematics image space data space Amplitude-preserved migration general formulation weighting function COMAZ ADCIG amplitudes spatial bandwidth temporal bandwidth RTT Applications true-amplitude migration inversion WEMVA
Reflection scheme: global view SourceReceiver V(x,y,z)
Reflection scheme: local view 2h v
ADCIG methods Reflection angleOffset ray-parameter k-domain (RTT) x-domain (slant-stack)
ADCIG: example
ADCIG methods: comparison Reflection angleOffset ray-parameter indirectly –function of dip directlyReflection angle less sensitivesensitiveInaccurate velocity boundaries data space –mixed with migration image space –separated from migration Computation domain
Agenda ADCIG kinematics image space data space Amplitude-preserved migration general formulation weighting function COMAZ ADCIG amplitudes spatial bandwidth temporal bandwidth RTT Applications true-amplitude migration inversion WEMVA
Spatial bandwidth khkh kzkz max max kzkz max max
Synthetic: ideal gather frequency domainspace domainamplitude
Temporal bandwidth imageangle gather dataoffset gather wide frequency band narrow frequency band kzkz khkh kzkz khkh khkh kzkz
Temporal bandwidth frequency domainspace domainamplitude
RTT implementation Two possibilities: –push: loop over input –pull: loop over output khkh kzkz kzkz angle gather offset gather
push RTT offset-gatherangle-gather k-domain x-domain
pull RTT offset-gatherangle-gather k-domain x-domain
RTT amplitudes
Agenda ADCIG kinematics image space data space Amplitude-preserved migration general formulation weighting functions COMAZ ADCIG amplitudes spatial bandwidth temporal bandwidth RTT Applications true-amplitude migration inversion WEMVA
Amplitude-preserving migration Definition: the process of recovering the amplitude of the reflectivity vector given –perfect data –infinite bandwidth –infinite aperture
Modeling operator L: modeling operator A: Amplitude operator G: Reflection operator i 0 : seismic image r: reflectivity d: seismic data
Amplitude operator Clayton & Stolt (1981) L: modeling operator A: amplitude operator G: Reflection operator i 0 : seismic image r: reflectivity d: seismic data
Reflection operator L: modeling operator A: amplitude operator G: reflection operator i 0 : seismic image r: reflectivity d: seismic data Clayton & Stolt (1981) Stolt & Benson (1986)
Amplitude-preserving operator L: modeling operator A: amplitude operator G: reflection operator i 0 : seismic image r: reflectivity d: seismic data
Weighting operator modelingmigration
Agenda ADCIG kinematics image space data space Amplitude-preserved migration general formulation weighting functions COMAZ ADCIG amplitudes spatial bandwidth temporal bandwidth RTT Applications true-amplitude migration inversion WEMVA
Amplitude correction: the problem frequency domainspace domainamplitude
Jacobian: general expression image space data space
Jacobian: 2-D, image space 2h v
Jacobian: general expression image space data space
Jacobian: 2-D, data space 2h v
Jacobian: 2-D, flat reflectors (Wapenaar et al., 1999)
Amplitude correction: the problem frequency domainspace domainamplitude
AVA: correct amplitudes frequency domainspace domainamplitude
Agenda ADCIG kinematics image space data space Amplitude-preserved migration general formulation weighting function COMAZ ADCIG amplitudes spatial bandwidth temporal bandwidth RTT Applications true-amplitude migration inversion WEMVA
COMAZ: stationary-phase view from above 2-DCOMAZ
Amplitude component Phase-shift component COMAZ: stationary-phase correction
COMAZ: no amplitude corrections
COMAZ: all amplitude corrections
Agenda ADCIG kinematics image space data space Amplitude-preserved migration general formulation weighting function COMAZ ADCIG amplitudes spatial bandwidth temporal bandwidth RTT Applications true-amplitude migration inversion WEMVA
True-amplitude migration L: modeling operator A: amplitude operator G: reflection operator i 0 : seismic image r: reflectivity d: seismic data
True-amplitude migration: COMAZ OPERATORS L: modeling W: Jacobian A: amplitude A stat : stationary-phase G: reflection
True-amplitude migration: real data
Inversion: pseudo-unitary operators InversionMigration
Inversion: preconditioned regularization
Wave-equation MVA L: Wave-equation MVA m: slowness perturbation d: image perturbation References: SEP100, SEP103, SEP105
WEMVA: model
WEMVA: correct amplitudes
WEMVA: incorrect amplitudes
Summary The goal –Reflectivity function of reflection angle The means –correct ADCIG transformations –kinematics –amplitudes –correct migration amplitude
Applications true-amplitude migration seismic inversion AVA wave-equation MVA