Patent GB-1069908-A (GB)
Title: Displaying seismic data
IPC: G01V1/24
Filed: 1964-07-03
Abstract: 1,069,908. Geophysical prospecting. PAN AMERICAN PETROLEUM CORPORATION. July 3, 1964 [Nov. 22, 1963], No. 27628/64. Heading H4D. [Also in Division G2] In a method for showing the correlation between a group of related seismic' traces derived using a common sub-surface reflection point, the traces are corrected for static and dynamic differences of seismic wave travel time with reference to a common datum and are then displayed as adjacent narrow traces which tend to merge into each other at normal viewing distances, whereby primary reflections appear as essentially continuous alignments of the corresponding sections of the traces while non-random interfering waves (such as multiple reflections, shear waves, layer- or boundary-guided waves, conversion waves and other reverberations) may appear as non-continuous alignments: It is stated that this arrangement enables errors to be shown up which would normally be masked by conventional electrical trace-compositing methods, enables the probable effect of the non-random waves on the desired reflections to be estimated, and enables the effectiveness of measures to reduce particular interfering wave types to be evaluated. In the embodiment of Fig. 1, corrected traces ready for display are stored on rotating magnetic drums 10. During one display Period, traces selected by a switching matrix 14 are read off by reproducing heads. 13 feeding into amplifiers. 15. The amplifiers 15 energize glow tubes 16 to expose , through a row of apertures in a mask 17, a series of variable density traces on a photographie recording medium 18 wrapped around, a drum 19 rotated insynchronism with the drums 10. In a second display period, the mask 17, and glow tube array 16 are shifted length-wise, as a unit along a lead screw 20 by an amount equal to the width of a mask aperture and a second, series of traces is recorded. The procedure is repeated to build up a. display as in Fig. 7 (not shown), comprising a series of groups of related traces. Each group may correspond to a different subsurface reflection point with adjacent traces in a particular group corresponding to systematically varied geophone positions or shot-points, or any other' grouping of the traces according to shot-point, geophone position and reflectionpoint may be arranged depending on the setting of the switching matrix 14. The width of the apertures in the mask 17 is selected according to the number of related traces per group (Figs. 2 and 3, not shown). Narrow-trace variable-area recording may be used instead of the variabledensity recording. In the embodiment of Figs. 4, 6 and 7 (not shown), for converting conventional variable-density, variable area or other constant width traces. into the required narrow trace form, a pair, of motor-driven rollers (32 and 33) draw a conventional thin-paper recording   ro transparency (31) in a direction perpendicular to the lenght of the traces past a narrow slit, (35), illuminated from above by a sources (41), to produce a recording on a photographic medium (36) wrapped around a rotating drum (37) The drum (37) is driven from the roller (32) through a speed reducer (39) whose reduction ratio determines the lateral compression-ratio of the final recording (36) relative to the recording (31). A combination of photographic reduction and lateral compression by the apparatus may be used to alter both the vertical (time) and horizontal (distance) scates of the recording (31).