Combination of Amplitude and Frequency Modulation for Communication in Seismograph Exploration for Petroleum Reservoirs

The reflection seismograph method of exploring and contouring various subsurface geological beds suitable for petroleum deposits is reviewed briefly. Instrumentation techniques are passed over briefly with the exception of equipment as described which is devised to transmit and receive by frequency modulation certain electrical impulses generated coincident with the detonation of the dynamite charge and with the arrival of the seismic impulse at the earth's surface immediately above the explosive charge. Amplitude modulation of voice signals was devised for transmission and reception over the same radio channel. The combination of the two schemes of modulation provided suitable voice reception without interfering with the frequency-modulation system to record the time break and uphole geophone electrical impulses free of static and accurate to 1/1000 of a second. The apparatus provides also for transmission of these impulses and voice signals by wire transmission with the same magnitude, clarity, and precision by means of simple switching arrangements. The 10-watt input amplitude-modulation-frequency-modulation transmitter devised is ample for the purpose up to 1 mile which is sufficient for reflection seismograph exploration.