GB934749A - Acoustical generator and seismic exploring system - Google Patents

Abstract

934,749. Generating combustion products under pressure. SOCONY MOBIL OIL CO. Inc. Nov. 18, 1959, No. 39187/59. Class 51 (1). [Also in Groups XXXVIII and XL (c)] An acoustical generator for producing seismic waves comprises a combustion chamber provided with an elongated open-ended extension piece for transmitting acoustic pulses into land or water, means for loading the chamber and the extension piece with a combustible gas mixture, and means for periodically igniting the gas mixture in the chamber so as to initiate a combustion wave which travels downward through the extension piece, the extension piece or means therein causing an increase in the velocity of the wave toward detonation velocity as it travels down the extension piece. The generator is particularly suitable for echo sounding and geophysical prospecting (see Group XL (c)). Combustible fluid, e.g. propane, enters mixing chamber 40, Fig. 3, via port 41 and oxygencontaining fluid enters via port 42; the fluids, which are under pressure, pass through screens 43a, 43b, forming a flame barrier, into ignition chamber 44 which incorporates a sparking-plug igniter. Elongated tubes 51 . . . 55 include elements, e.g. 56, with tapered bores to couple the elongated tubes to further tubes, e.g. 59. Once ignition is established, the flame front proceeds rapidly down the elongated tubes with an increasing speed exceeding that of sound and detonation occurs. The length/diameter ratio of tubes 51 ... 55 lies between forty and eighty. The fluid mixtures may alternatively be hydrogen and air or oxygen, or acetylene and air or oxygen; atomized liquids may also be used. Over land areas it is preferred to couple the generator via a pool of water, since this is stated to lead to higher energy efficiency and to reduction of noise due to air waves. Or a bag of coupling liquid in a flexible container attached to the generator may be provided, Fig. 6 (not shown). Substantially continuous flow of combustible mixture under pressure is stated to prevent ingress of the coupling liquid. To increase wave frequency and reduce pulse energy in shallow strata prospecting only one elongated tube is made effective, Fig. 8 (not shown). The frequency content of the pulses is varied by changing the richness of the combustible mixture. Pulse rates in the range 100 to several thousand per second may be employed.