Exxonmobil Upstream Research Company

Exxonmobil Technology and Engineering Company

Jonathan Liu

Jerome R Krebs

Spyridon K Lazaratos

Reeshidev Bansal

Hongchuan Sun

Lorie K Bear

Eric G Wildermuth

Velocity tomography using time lags of wave equation migration is disclosed. Seismic tomography is a technique for imaging the subsurface of the Earth with seismic waves by generated a migration velocity model from a multitude of observations using combinations of source and receiver locations. The migration velocity model may be updated in order to reduce depth differences of reflection events (also called residual depth errors (RDE)). Direct measurement of RDE may be difficult in certain complex subsurface areas. In such areas, the RDE may be reconstructed based on time lags of wave equation migration and then used to update the migration velocity model. In particular, the RDE may be directly reconstructed from the time lags of wave equation migration, such as based on a direct relation between RDE and the time lags.

Velocity tomography using time lags of wave equation migration

A method, including: obtaining a velocity model generated by an acoustic full wavefield inversion process; generating, with a computer, a variable Q model by applying pseudo-Q migration on processed seismic data of a subsurface region, wherein the velocity model is used as a guided constraint in the pseudo-Q migration; and generating, with a computer, a final subsurface velocity model that recovers amplitude attenuation caused by gas anomalies in the subsurface region by performing a visco-acoustic full wavefield inversion process, wherein the variable Q model is fixed in the visco-acoustic full wavefield inversion process.

Q-compensated full wavefield inversion

Method for building a subsurface model of velocity or other elastic property from seismic reflection data using tomography. The method uses velocity scans to pick a focusing velocity model at each image point (). The focusing velocities are used to pick depth errors from tables () generated using a tomographic inversion matrix () and a suite of different velocity models (). The depth errors are then reconstructed at each image point from the velocity scans based on the difference between the base velocity model and the most coherent velocity from the scan (). The reconstructed depth errors are used to compute the velocity model update ().

Velocity tomography using property scans

Method for reducing instability and increasing computational efficiency in tomographic inversion for velocity model building. A system of tomographic equations is developed for a uniform grid. A non-uniform parameterization is found for which a linear mapping exists between the space of the uniform grid and the space of the non-uniform grid. The matrix that relates velocity to the tomographic data in the non-uniform representation is then given by the matrix product of the corresponding matrix in the uniform grid representation and the mapping matrix. Inversion can then be performed for the non-uniform parameterization on a smaller, more stable matrix.

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Houston, TX, United States of America

Jonathan Liu