A method of seismic data processing is described in which a particular wavelet is selected from a plurality of wavelets as being most characteristic of a received seismic signal. A subtracted signal can be determined by subtracting a weighted signal of the particular wavelet from the received signal. From the subtracted signal, an additional particular wavelet can be chosen. The process of subtracting a signal and determining an additional particular one of the plurality of wavelets can be repeated until a criterion is met. The method can be repeated at several depths. The resultant spectral analysis can be used to determine, for example, an absorption coefficient.
The invention relates to a method for the detection and exploration of subterranean hydrocarbon deposits by receivers of acoustic waves in a frequency range from 0.2-30 Hz arranged at or near the surface, whereby, according to the invention, acoustic signals are recorded for a period of time T, subjected to a frequency analysis in time windows shifted by a period of time .DELTA.t, according to which each time window is subdivided into frequency channels and at least two frequency groups and then the amplitude values of the frequency channels of the frequency groups are correlated and the time deviation .tau. is determined for the first peak of the correlation function that is unequal to zero, and the ratio of the variation of the amplitude values of the peaks of the frequency groups from one time window to at least one other is determined for this time deviation .tau. and used to derive the magnitude of the hydrocarbon deposit, and the depth is calculated from the time deviation .tau..
The transfer function of the communication channel in a mud pulse telemetry system is determined by sending a known signal through the channel and spectral analysis of the received signal. The known signal may be a chirp signal or a stepped frequency signal. Based on the determined transfer function, operating parameters of the pulser are adjusted.
The method for exploring desired characteristics of a subsurface sector, having at least one resonant frequency, is based on selectively transmitting suitable narrowband energy waves into the subsurface sector, thereby producing narrowband signals reflected off the subsurface sector. The transmitted narrowband energy waves can be selectively and optimally adjusted in real time so as to provide optimum illumination of the desired characteristics from the explored sector.
