Abstract: In seismic exploration, refracted seismic energy is detected by seismic receivers to produce seismograms of subsurface formations. The seismograms are produced by directing seismic energy from an array of sources at an angle to be refracted by the subsurface formations and detected by the receivers. The directivity of the array is obtained by delaying the seismic pulses produced by each source in the source array.

Abstract: A seismic exploration process consisting of the application to the surface of the soil of a plurality of vertical impacts at points separated by a vertical trench cut into the soil. The vibrations propagating in the soil as a result of said impacts are then recorded, with the longitudinal wave components being eliminated from consideration. This makes it possible to produce agitation having a strong transverse wave component.

Abstract: Firing of a seismic source of the type called an air gun is detected by means of a fluid pressure sensor located in the housing of a solenoid actuated control valve. Through a pressurized gas support port the pressure sensor is in fluid contact with a shuttle-operating chamber of the air gun, and the sensor detects a surge in fluid pressure resulting from rapid motion of the shuttle. if a misfire or malfunction of the air gun is detected by means of the fluid pressure sensor, the malfunctioning air gun can be shut down by actuating the solenoid valve, which is a novel dual action solenoid valve, thereby preventing pressurized gas from being supplied to that particular air gun. The valve includes a valve stem with radial gas inlet ports and radial triggering ports. A solenoid plunger is movable to close one or the other of the sets of ports.

Abstract: A powerful seismic impulse is generated in a body of water by a slug of water propelled from a seismic source by expanding pressurized gas, but the gas is retained in the source for use in subsequent firings. The seismic energy source, which is called a "hydro gun", is recharged by pumping an incompressible liquid, preferably, water, at high pressure into the gun to compress the retained pressurized gas. The hydro gun includes a firing cylinder, and a piston follower in the firing cylinder divides it into a liquid-charge chamber and a gas-propulsion chamber. The liquid-charge chamber is closed from liquid discharge ports by a shuttle which is held closed by the high pressure of gas in an operating chamber. By pumping an incompressible liquid into the liquid-charge chamber, the follower is forced to compress the pressurized gas which is trapped in the gas-propulsion chamber.

Abstract: In marine seismic exploration, measurements of reflectivity and water depth are made from seismograms produced by the firing of a seismic energy source towed by a marine vessel. The measurements are made by generating the auto-correlation coefficients of a window of the seismogram and combining these coefficients for different time lags. The time lag producing the minimum energy in the combined autocorrelation coefficients represents water depth. The reflectivity of the water bottom is obtained by generating an estimate of the reflectivity from the values of the auto-correlation function of the window, and modifying this estimate by a factor which converts the estimate to the reflectivity. The measured water depth and reflectivity are converted into an inverse operator. A linear array of sources is then fired in a sequence such that the acoustic pulses combine to produce a resultant acoustic pressure wave having the inverse time domain operator characteristics.

Abstract: In seismic exploration, particularly at sea, several seismic acoustic sources selected from different genera of such sources are combined in a single array. The several sources are fired substantially simultaneously so that the acoustic pulses from the several sources blend together to create a single composite seismic wave. The source genera are selected such that their initial impulses are in phase but their caudal transients are incoherent with respect to one another so that the initial impulse is enhanced at the expense of the after-pulses.

Abstract: In marine seismic exploration, seismograms recording reflected energy generated from the firing of a seismic source are used to measure the characteristics of the medium through which the energy passes. These measurements are converted into control parameters for an array of seismic sources. When the array is fired under control of these parameters, seismograms having enhanced reflections are produced. As an example, at least one seismic source is fired to produce seismograms which are used in the measurement of water bottom reflectivity and water depth. The measured reflectivity and water depth are converted into a time domain operator representative of the inverse of the reverberation distortion in the water layer. An array of sources is then fired in a sequence which produces an acoustic pressure wave having the inverse time domain characteristics.

Abstract: The invention concerns a process for seismic exploration. It consists in simultaneously emitting disturbances from a plurality of sources S1 . . . Sn immersed at various depths and positions chosen so as to maximize the power transmitted vertically and to minimize the power transmitted in certain determined oblique directions. The reflected or refracted seismic signals are gathered by hydrophones. By this means certain parasitic refractions are eliminated.

Abstract: In marine seismic exploration, a long array of sources efficiently transfers energy along the reflection path. Multiple reflection rejection is achieved by normal move-out discrimination at selected trace distances for each reflection. The length of the source array is changed in accordance with the geological characteristics of the sub-surface formations being explored and the reflection time of reflections from formations of interest. A split source array allows one section of the array to be moved with respect to the other to change the overall length of the array without changing the number of sources which are fired. Primary to multiple reflection enhancement is obtained by selecting only traces having source to detector offset distances with a primary to multiple amplitude response ratio greater than one.

Abstract: A system for marine seismic exploration has arrays of sources and receivers which discriminate against horizontal traveling source-generated noise. Directive arrays of sources or receivers have a length which is longer than the wavelength of the lowest frequency of the seismic pulse. The spacing between the elements in the array is less than the wavelength of the highest characteristic frequency in the seismic pulse.

Abstract: A method and apparatus for simultaneously towing and handling multiple airguns are disclosed for use in marine seismic surveying which provide for ease in handling large numbers of airguns and enable them to stream out at a desired depth behind a submerged towing head in a long flexible streamer, or a plurality of simultaneously towed airgun streamers, whose level below the surface can be changed, if desired, while the survey is progressing. A plurality of airguns are included in each streamer extending for a length behind the survey vessel for providing an effective geographic diversity in the location of the airguns which can be simultaneously fired, or can be fired with time delay, for generating very powerful large area seismic energy wavefronts travelling down through the body of water. The buoyancy of the airgun streamer is controllable to provide neutral buoyancy during towing, if desired, and slight positive buoyancy to float the streamer in preparation for taking it on board the towing vessel.

Abstract: Disclosed is an improved air gun construction which lends itself to use with a plurality or array of similarly improved air guns which enables easy synchronization and timing of such array of air guns relative to one another. In the preferred embodiment, the air gun comprises a shuttle having magnetic properties and an electrical coil in proximity to said shuttle. When the air gun is actuated and the shuttle is accelerated, a voltage is induced in the coil by the flux lines from the magnetized shuttle moving through the turns of the coil. Electrical circuit means associated with each gun senses when a predetermined voltage is induced in the coil and generates a timing signal for each air gun. Additional electrical circuit means phases each of the timing signals from the air guns to occur at a predetermined time to thereby insure firing each of the air guns accurately.

Abstract: Apparatus for effecting and controlling the firing of energy sources, particularly is seismic work, includes means for automatically correcting the delays between the desired and actual firing times which may be different for different sources. These means comprise a number of programmable counters for initiating the firing of different sources, a reference time counter to indicate the desired firing time or times and comparator means responsive to differences between actual and desired firing times to cause the programmable counters to bring the actual firing times towards the desired firing times.