Walkaway VSP calibrated sonic logs
AssigneeSchlumberger Technology Corporation
InventorsStephen Allan Horne, Paolo Primiero
Life of this patent
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Abstract
Methods and related systems are described relating to processing subsurface sonic and seismic data. The described techniques use anisotropy estimates derived from a walkaway VSP to calibrate elastic properties derived from sonic logs. An empirical relationship between the sonic derived anisotropy parameters is modified until the upscaled elastic properties from the sonic log data best matches the anisotropy parameters measured with the walkway VSP. The result is a set of elastic constants consistent with the walkaway VSP measurements.
Claims20
A method for processing subsurface data comprising:
- receiving seismic data representing measurements made of seismic energy that has passed through a subsurface formation;
- receiving sonic data representing measurements made of sonic energy that has passed through the subsurface formation;
- making a first assumption with respect to the subsurface formation based at least in part on the sonic data, wherein the first assumption includes a relationship between sonic anisotropy parameters of the sonic data;
- calculating, by a processor and based on the assumed relationship and the sonic data, one or more elastic constants that can be used to describe anisotropy of the subsurface formation;
- calculating one or more sonic anisotropy parameters of the sonic data based on the one or more elastic constants;
- comparing the one or more sonic anisotropy parameters of the sonic data with one or more seismic anisotropy parameters of the seismic data so as to determine if the first assumption is acceptable based on a metric;
- altering the first assumption if the first assumption is not acceptable;
- and
- outputting a log of the sonic data based at least in part on the calculated elastic constants if the first assumption is acceptable.
A system for processing subsurface data comprising a processing system programmed and configured to:
- receive seismic data representing measurements made of seismic energy that has passed through a subsurface formation;
- receive sonic data representing measurements made of sonic energy that has passed through the subsurface formation;
- make a first assumption with respect to the subsurface formation based at least in part on the sonic data, wherein the first assumption includes a relationship between sonic anisotropy parameters of the sonic data;
- calculate, based on the assumed relationship and the sonic data, one or more elastic constants that can be used to describe anisotropy of the subsurface formation;
- calculate one or more sonic anisotropy parameters of the sonic data based on the one or more elastic constants;
- compare the one or more sonic anisotropy parameters of the sonic data with one or more seismic anisotropy parameters of the seismic data so as to determine if the first assumption is acceptable based on a metric;
- altering the first assumption if the first assumption is not acceptable;
- and
- outputting a log of the sonic data based at least in part on the calculated elastic constants if the first assumption is acceptable.
Dependencies are inferred from the claim text.