IDENTIFICATION AND CLASSIFICATION OF SEISMIC REFLECTION VELOCITY PROPERTIES ON SEISMIC REFLECTION SECTIONS

摘要

1293220 Seismic signal processing PETTY GEOPHYSICAL ENG CO 29 Dec 1970 [5 Jan 1970] 61534/70 Heading H4D A seismic reflection display which includes velocity information is prepared automatically by plotting processed seismic signals as a time or depth section, plotting an overlay representative of interval velocity data and having horizontal and vertical scales in the same ratio as for the seismic section, and superimposing the overlay (e.g. an opaque sheet or a transparency, superimposed directly or by optical projection) on the seismic section. In the Fig. 6 example the seismic section is a depth section and the overlay is in the form of iso-time lines 602 . . . 612. Each such line represents the profile of a hypothetical reflector giving the same two-way seismic travel time at different points along a traverse, taking into account velocity charges such as those due to low velocity zone 601. In the Fig. 5 example the seismic section is a time-section and the overlay is in the form of iso-depth lines such as 102. By comparison with line 102, line 134 is seen to represent a dipping reflector and is not falsely interpreted as showing a structural high below the point 0.5 miles along the traverse. The overlay is preferably coloured differently from the seismic section. Several overlays may be prepared, based on different velocity functions. It is stated that velocity data may be obtained from well logs or from the seismic reflection signals. An overlay based on the velocity down to a reflector causing multiple reflections and on the same velocity for all deeper depths may be used to identify multiple reflections in the seismic section. An automatic data processing system is described in which (a) digitally recorded common depth point (CDP) seismic reflection signals are processed to obtain interval velocity data, (b) normal moveout corrections based on these velocity data are applied to the signals and the corrected CDP signals are stacked, (c) the stacked signals are subjected to further processing including deconvolution and filtering, (d) the processed signals are plotted as a time or depth section, (e) iso-depth or iso-time values are computed from the interval velocity data and (f) these values are plotted as an overlay transparency.