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Volume 10,     Number 2,     Summer 2002

 

LEAST-SQUARES SEISMIC MIGRATION USING WAVEFIELD PROPAGATORS FOR AVP INVERSION
HENNING KUEHL AND MAURICIO D. SACCHI

Abstract. The imaging of geological subsurface structures with seismic reflection energy is a powerful tool for the detection and the assessment of hydrocarbon reservoirs. The seismic method can be understood as a multi-source and multi-receiver reflection scattering experiment. The seismic sources and receivers are placed at the earth's surface. The sources emit seismic energy into the subsurface and the receivers record the earth's response (the backscattered energy) as a function of time and position relative to the source. The goal of seismic imaging is to invert the recorded seismograms for the subsurface structures and their underlying lithological properties. Seismic imaging is usually called migration when only structural image information is desired. The term inversion is used if the goal is to invert for physical properties of the subsurface. In this paper, we do not attempt to invert for true physical parameters. Instead, we aim at preserving the angle or the closely related ray-parameter dependence of migrated seismic data. In a subsequent step, this information can then be used to invert for the lithological parameters that determine the angle/ray-parameter dependent subsurface reflectivity. In the framework of linearized scattering theory seismic data modelling and migration is defined as a pair of adjoint operators. This definition leads to the formulation of an iterative least-squares seismic migration method. The modelling/migration operator pair is implemented using a wave eld propagator technique. We propose least-squares migration with a regularization term that imposes continuity on amplitude variations as a function of ray-parameter (AVP). This regularization is based on the idea that roughness along the ray-parameter axis stems from numerical artifacts and incompletely and/or irregularly sampled seismic wave fields. A synthetic seismic data example is given for illustration.

 

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