Abstract: This application relates to seismic data gathering devices and to testing the impedances of the geophone channels of such devices. The invention includes impressing a test current on each channel to be tested, said current developing a test voltage indicative of the impedance; generating a high reference voltage which corresponds to the maximum acceptable impedance of the channel; generating a low reference voltage which corresponds to the minimum acceptable impedance of the channel; and comparing the test voltage with the reference voltages.

Abstract: A method and apparatus for improving the power output of a seismic vibrator are provided. Compliant elements with variable stiffnesses are interposed between and connected to the holddown mass and the baseplate. When the compliant elements have a first stiffness, the vibrator-earth system has a first resonant frequency. When the compliant elements have a second stiffness, the vibrator-earth system has a second resonant frequency. During sweep, the compliant elements are set on the first stiffness until the vibrator has passed through the first resonant frequency; then the compliant elements are changed to their second stiffness and the sweep continues through the second resonant frequency.

Abstract: An open-ended seismic source for use in a liquid medium such as water is disclosed. The source includes a source of explosive gas, a firing chamber connected to the source, a capacitor discharge ignition system connected to the firing chamber for igniting the gas in the firing chamber, a barrel connected to the firing chamber, defining an explosion chamber and having an outlet at its lower end, a plurality of baffle plates fixed in the barrel near the outlet for permitting the exploded gas to enter the medium and for retarding the entry of the medium into the barrel, and a reaction plate attached to the barrel and disposed below the outlet so that the exploded gas entering the medium impinges on the plate and the recoil of the barrel is reduced.

Abstract: A method is disclosed for determining the relative amounts of two fluid phases in a subterranean formation, one phase being mobile and the other being substantially immobile. A sweep fluid which is substantially free of the immobile fluid is injected into the formation by means of a well in an amount such that a measurable first portion of the sweep fluid in the formation adjacent the injection well remains unsaturated with the immobile fluid, and a second portion adjacent the first portion becomes saturated. The sweep fluid is then produced from the formation, preferably by means of the injection well. The concentration of immobile fluid dissolved in the produced sweep fluid is measured as a function of volume produced to determine the volumes of the two sweep fluid portions; these volumes are then used to calculate the relative amounts of the two fluid phases in the formation.