Abstract: The present invention provides a method for determining net-sand thickness and net-reservoir volume over a broad range of gross sand thickness in a target zone. A net-resource attribute is designed to estimate net-sand thickness based upon the inner product of the determined probe function and the segment of the seismic trace that includes the target zone. The net-resource attribute and the geographic location for each trace can be stored and a net-resource table may be created. Maps and net-reservoir volume can be generated from the geographical location information and the net-resource attributes. Net-sand thickness allows the determination of the total volume of sand and thus the size of the hydrocarbon container or the net-reservoir volume.

Abstract: The present invention provides a method for determining net-sand thickness and net-reservoir volume over a broad range of gross sand thickness in a target zone. A net-resource attribute is designed to estimate net-sand thickness based upon the inner product of the determined probe function and the segment of the seismic trace that includes the target zone. The net-resource attribute and the geographic location for each trace can be stored and a net-resource table may be created. Maps and net-reservoir volume can be generated from the geographical location information and the net-resource attributes. Net-sand thickness allows the determination of the total volume of sand and thus the size of the hydrocarbon container or the net-reservoir volume.

Abstract: A method of measuring the propagation velocity of one or more of a plurality of different types of elastic waves in a borehole. It employs a source of elastic waves at a given location in a borehole. The elastic waves generated have a given known frequency. There are a plurality of receivers spaced at different distances from the source. The signals developed by the receivers are digitally multiplexed at a high scan rate relative to the generated frequency. Then the multiplexed signals are analyzed to determine the wave lengths of the received signals. From the wave lengths the propagation velocities, v, may be computed by using the fundamental relationship v=f.lambda., in which f is the frequency and .lambda. is the wave length.

Abstract: A method, when practiced, enhances seismic data so as to suppress noise in the seismic data. The seismic data was generated in a conventional manner by at least one receiver apparatus whose position does not substantially change. The method includes combining at least two elementary seismograms to form noise seismograms containing little or none of the desired signal. The number of different noise seismograms so derived is at least equal to the number of elementary seismograms to be combined to form a final seismogram. The probability distribution of noise is determined for each trace of the noise seismograms from the probability distributions of noise in the traces of the noise seismograms. The most probable form of the desired signals is derived from the probability distribution of noise in the traces of the elementary seismograms to provide the enhanced seismic data.

Abstract: A method determines the extent of subsurface reactions in which random acoustic signals are radiated from a whole area covered by the reaction or from a boundary region, hereafter termed reaction front, between largely undisturbed rocks and those already covered by the reaction. The signals are recorded by at least two receivers positioned at different locations outside the reaction area. The recorded signals are cross-correlated as a function of a time shift between the recorded signals so that at least one surface confining the reaction area is determined from the cross-correlation.

Abstract: A method is provided for obtaining wide band seismograms made from a plurality of narrow band seismic surveys using vibrator type sources. Several different narrow frequency band seismograms are obtained using vibrator type signal sources. The narrow band seismogram having different frequency band responses are stacked, or added together, to provide a single wide band seismogram having improved signal to noise characteristics.

Abstract: The apparatus and method provides for an improvement to a system which converts wide amplitude range digital data recorded in floating point digital word form to analog signals within a limited amplitude range. The apparatus and method provides for the situation wherein the digital data can represent an analog signal for which on a general decrease in amplitude increases may be superimposed. The apparatus includes a digital/analog converter whose reference voltage is individually determined for each sample. This reference voltage is taken from a saw tooth oscillator at an instant of time determined by a delay timer which responds to changes, with respect to a desired average amplitude, of the actual amplitude of the converted data.

Abstract: Apparatus and method determines the time shift and total phase difference between two alternating current signals. A value .psi. (f) corresponding to the phase relationship between the two signals is determined for each frequency f contained in the two signals. A slope A and an ordinate section B of the best fitting straight line g(f)=Af + B through the totality of the values .psi. (f) so obtained is determined. The phase shift .psi..sub.o =B modulo (2.pi.) is determined from the ordinate section B and the time shift .tau. = A/2.pi. from the slope A.

Abstract: A method of suppressing noise trains that develop from harmonics of a vibrator-type sweep signal. It includes the step of generating a plurality of such sweep signals in series and with the phase of each succeeding sweep signal being shifted relative to the previous one by a predetermined phase angle which is a fraction of 2.pi.. The generated signals are separately recorded and transformed by inverse phase shifting before being added or stacked in a conventional manner.