Abstract: To eliminate undesirable energy recorded during seismic surveying, a trace that models the undesirable energy on the recorded data trace is prepared. The model trace is first estimated using a suitable technique, such as wavefield extrapolation. Then, the model trace is modified using a best estimate of the amplitude, phase and time delay differences between the model trace and the data trace. The estimated amplitude, phase and time delay differences may be used to design a cross-equalization filter, which is used to cross-equalize the model trace with the data trace. Alternatively, the best estimate determination may include using a weighted sum of the model trace, its imaginary component, and their derivatives. When weighted and summed together, these components form a cross-equalized model trace that closely approximates the undesirable energy on the recorded data trace. Lastly, the cross-equalized model trace is subtracted from the data trace to substantially eliminate the undesirable energy.

Abstract: The present invention provides method of interpolating spatially aliased seismic data. This method produces high resolution interpolated data based on a locally planar model of reflection events using a two dimensional power diversity slant stack process that transforms the data from the t-x-y domain to t-xslope-yslope domain. The present invention further provides an improved technique for the 3D interpolation of aliased events and is applicable to the interpolation of 2D seismic data.

Abstract: A method for attenuating coherent and incoherent noise in seismic signal data is provided. Seismic signal data is transformed from a time-space domain using a Radon-transform domain. In the Radon-transform domain, coherent noise is attenuated by muting and incoherent noise is attenuated by diversity stacking. Data remaining in the Radon-transform domain in transformed back to the time-space domain by an inverse Radon transform.

Abstract: A system of monitoring the fluid contents of a petroleum reservoir, wherein a reservoir model is employed to predict the fluid flow in the reservoir, includes a check on the reservoir model by comparison of synthetic seismograms with the observed seismic data. If the synthetic output predicted by the model agrees with the observed seismic data, then it is assumed that the reservoir is being properly worked. If not then the reservoir model, in particular its reservoir description, is updated until it predicts the observed seismic response. The seismic survey may be periodically repeated during the productive life of the reservoir and the technique used to update the reservoir model so as to ensure that the revised reservoir description predicts the observed changes in the seismic data and hence reflects the current status of fluid saturations. Implementation of this invention results in more efficient reservoir management.

Abstract: A method for carrying out dip moveout correction on seismic data which provides true-amplitude seismic images is provided. A calibration process is used to design a set of filters that correct the seismic amplitudes during dip moveout correction so as to provide true-amplitude imaging. These filtrs can be designed and applied in any known implementation of dip-moveout, in three or two dimensions.

Abstract: A vibrator seismic source has a hydraulic system, including a pad, for applying reciprocating forces to the ground and sensor means for generating a feedback signal representative of the force applied to the ground. Circuitry is provided for generating a pilot signal representative of the desired force to be applied to the ground. The pilot and feedback signals are single sideband shifted to increase both frequencies by a predetermined frequency. The high frequency pilot and feedback signals have their phase difference conventionally detected and provided to a digital computer for phase shifting the signal for controlling the vibrator so that the feedback signal is in phase with the pilot signal. In another embodiment, the instantaneous phase of each signal is computed continuously by a digital computer. The control signal digital representation is corrected to correspond with the pilot digital representation and an analog output signal is generated to provide the proper analog control signal.

Abstract: A vibrator seismic source has a sweep generator for providing a pilot signal and sensors for generating a feedback signal representative of the force imparted to the ground by the vibrator pad. Circuitry is incorporated for separating the fundamental signal from the feedback signal and for separating the distortion from the feedback signal. Means are provided for generating a control signal for controlling the action of the vibrator, the control signal being reduced or increased by the difference between the pilot signal and the fundamental signal, and further reduced by the distortion, if any. A threshold circuit is employed to ignore distortion below the threshold level and a threshold circuit is provided to ignore differences in amplitude between the pilot and fundamental signals when the difference is below the threshold. Additionally, the control system employs a phase detector circuit that outputs any phase difference between the feedback and pilot signals.

Abstract: A method of seismic prospecting is disclosed in which the seismic source is excited in such a manner as to maximize the use of the energy generated by the seismic source. In certain cases it may be desirable to convert the received seismic signals to their frequency domain counterparts before performing subsequent processing. Such conversion may be performed using the discrete Fourier transform with the result that transformed values are obtained only at certain discrete frequencies. It may further be desirable that processing be performed only at subsets of the total set of discrete frequencies with the values at the remaining frequencies being discarded. In the practice of the present invention, source energy is generated only at those discrete frequencies at which subsequent processing is to be performed. As a result there is substantially no source energy in the transform values at the frequencies which are discarded.