| 摘要 |
1,111,911. Seismic prospecting. ATLANTIC RICHFIELD CO. 10 Jan., 1966 [29 Jan., 1965], No. 1122/66. Heading H4D. In a method for compositing a plurality of seismic traces recorded using a corresponding plurality of horizontal spacings of shot-point and geophone and using a common subsurface reflection point, static and dynamic corrections are applied to the traces and the effect of frequency distortion due to the dynamic corrections is substantially eliminated from the summation of the corrected traces by suppressing initial sections of the corrected traces where dynamic corrections are greater than a predetermined value. The dynamic correction to be applied to a trace increases with the shot-point to geophone spacing and decreases with increased depth of the reflecting subsurface formation, and is thus a function of the angle of reflection of a seismic signal at a subsurface formation. In one embodiment, trace sections involving reflection angles greater than 35 degrees are suppressed, sections involving angles between 20 and 35 degrees may optionally be suppressed or suppressed to a lesser degree, and sections involving angles less than 20 degrees are included in their entirety in the summation process. The percentage change in frequency of a seismic signal as a result of time delays imposed in making the dynamic corrections is proportional to the time delay, and in a preferred embodiment those trace sections involving a frequency change of 10% or more are suppressed, those involving a change of between 5 and 10% may optionally be suppressed or suppressed to a lesser degree, and those involving a change of less than 5 % are not suppressed. The frequency change is determined by comparing visual records of the original seismic data and the corrected seismic data. A visual record is prepared from the composite of the unsuppressed traces and unsuppressed trace sections. Details of a circuit for suppressing the initial section of a trace for a selected length of time are given. |
