SYNTHETIC SEISMOGRAMS FOR GENERALIZED SHOT—DETECTOR GEOMETRY OVER OIL AND GAS TRAPS

Abstract

Geophysicists have long sought reliable means of detecting the presence, far below the ground, of natural gas and possibly oil too. Although direct location of oil without drilling seemed to be an impossible dream, no one had dared claim the ability to do so even in the early days, over a century ago, when water deviners were successfully hawking their services to credulous wild catters. Today there appears to be a distinct possibility of obtaining and decipherning direct messages from di l and gas horizons. Seismic energy may be introduced in the earth by a variety of sources, usually artifically created explosions. This energy travels outward from the focus of the disturbance much like light rays from a source and suffer reflection and refraction whenever variations in densities and velocities such as those produced by lithological discontinuties are encountered. Until recently, only the arrival times of echoes returned to the surface by buried geological reflectors has been generally used in reflection seismic mapping. A careful analysis of their travel times yields a fairly good indication of the shape and composition of buried rock strata, from which one may infer the presence (or absence) of traps favourable for the accumulation of oil or gas or both. Success achieved by this procedure in India is about 40 percent........