Exxonmobil Upstream Research Company

David L Hinkley

Jerome R Krebs

John E Anderson

Ramesh Neelamani

Thomas A Dickens

Christine E Krohn

Charlie Jing

Peter Traynin

Anatoly I Baumstein

Sunwoong Lee

Charles Jing

Method for reducing the time needed to perform geophysical inversion by using simultaneous encoded sources in the simulation steps of the inversion process. The geophysical survey data are prepared by encoding () a group of source gathers (), using for each gather a different encoding signature selected from a set () of non-equivalent encoding signatures. Then, the encoded gathers are summed () by summing all traces corresponding to the same receiver from each gather, resulting in a simultaneous encoded gather. (Alternatively, the geophysical data are acquired from simultaneously encoded sources.) The simulation steps needed for inversion are then calculated using a particular assumed velocity (or other physical property) model () and simultaneously activated encoded sources using the same encoding scheme used on the measured data. The result is an updated physical properties model () that may be further updated () by additional iterations.

Iterative inversion of data from simultaneous geophysical sources

A method for efficient inversion of measured geophysical data from a subsurface region to prospect for hydrocarbons. Gathers of measured data () are encoded () using a set of non-equivalent encoding functions (). Then all data records in each encoded gather that correspond to a single receiver are summed (), repeating for each receiver to generate a simultaneous encoded gather (). The method employs iterative, local optimization of a cost function to invert the encoded gathers of simultaneous source data. An adjoint method is used to calculate the gradients of the cost function needed for the local optimization process (). The inverted data yields a physical properties model () of the subsurface region that, after iterative updating, can indicate presence of accumulations of hydrocarbons.

Efficient method for inversion of geophysical data

Method for converting seismic data to obtain a subsurface model of, for example, bulk modulus or density. The gradient of an objective function is computed () using the seismic data () and a background subsurface medium model (). The source and receiver illuminations are computed in the background model (). The seismic resolution volume is computed using the velocities of the background model (). The gradient is converted into the difference subsurface model parameters () using the source and receiver illumination, seismic resolution volume, and the background subsurface model. These same factors may be used to compensate seismic data migrated by reverse time migration, which can then be related to a subsurface bulk modulus model. For iterative inversion, the difference subsurface model parameters () are used as preconditioned gradients ().

Methods for subsurface parameter estimation in full wavefield inversion and reverse-time migration

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Spring, TX, United States of America

David L Hinkley