Patent ID: 11899151
Assignee: PGS GEOPHYSICAL AS
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 31:
32. In a technological process in which images from a monitor seismic survey are generated for comparison with images from a baseline seismic survey to detect changes in subsurface characteristics, wherein the monitor survey occurs after the baseline survey, the specific improvement comprising:
performing a transition survey using first and second different source types, the first type corresponding to a type used in the baseline seismic survey, and the second type corresponding to a type used or to be used in the monitor survey;
determining differences between signals recorded from the first and second source types during the transition survey; and
using the differences to adjust sensor signals from at least one of the baseline survey and the monitor survey, thereby enabling the generation of a monitor survey image and a baseline survey image such that differences between the images indicate changes in geological structures and not changes in seismic source types;
wherein the transition survey comprises a 4D seismic survey relative to at least one of the baseline survey and the monitor survey, such that both the transition survey and the at least one survey employ seismic sensors spaced apart in an inline direction and in a crossline direction, and such that an elapsed time between the transition survey and the at least one survey is sufficiently long to allow detectable changes in the subsurface characteristics to occur between a time of the transition survey and a time of the at least one survey.