Resolution enhancement with relative amplitude preservation for unconventional targets

Our primary objective was to evaluate a method that enhances the resolution of 3D seismic data that does not disturb the relative amplitude preservation. The formations that are the subject of the analysis are Lower Silurian: the Jantar Formation and the Ordovician Sasino Formation (the onshore part of the Baltic Basin, northern Poland). Both formations are seismically thin layers and have been recent targets for unconventional exploration. Resolution enhancement designed to help the structural interpretation may enable precise structural interpretation of thinly layered intervals. The method that we applied is poststack spectral blueing. To verify the effectiveness of the spectral blueing procedure, we designed an algorithm that compares the amplitude values along evenly distributed seismic traces. The algorithm addresses the preservation of the relative amplitude ratio. We did not want to disturb the amplitude values by the enhancement algorithm and introduce information that would be false for seismic inversion analysis. Hence, it was crucial for us to obtain the enhanced seismic volume suitable for structural interpretation that holds relative amplitude relation criterion. The algorithm helped obtain the optimal enhanced seismic volume that is preferable for the structural interpretation of seismic data and possibly could be used successfully for a seismic inversion process. With the optimal enhanced seismic volume, we were able to conduct a more accurate structural interpretation — an entirely new seismic horizon that indicates that the top of one of the formations under analysis was clearly visible and thus possible for interpretation. We applied the acoustic inversion to the original and the enhanced seismic data — the latter enabled the determination of two additional anomalous zones that had not been previously possible to distinguish within the seismic volume.

Nonstationary differential resolution: An algorithm to improve seismic resolution

High-resolution seismic data enables better well ties, structure delineation, stratigraphic mapping, and reservoir characterization. Differential resolution (DR) is a data-driven method to improve seismic resolution, but it can introduce a false spatial amplitude variation in the seismic output due to whole trace normalization. The newly proposed normalization technique decomposes the input seismic trace using a translating Gaussian window and then implements the DR algorithm on each window. The introduced weight factors give the interpreter control of the degree of spectral broadening. These developments enable the algorithm to account for the nonstationary properties of the seismic trace, reduce spurious spatial amplitude variation, and provide broader bandwidth seismic data for detailed analysis. We described the mathematical derivation of the nonstationary differential resolution (NSDR) algorithm and its implementation on synthetic and real seismic data. A comparison of NSDR with the original and DR shows better relative amplitude preservation.

Generalized staining algorithm for seismic modeling and migration

The staining algorithm is introduced to improve the signal-to-noise ratio (S/N) of poorly illuminated subsurface structures in seismic imaging. However, the amplitudes of the original and the stained wavefield, i.e., the real and the imaginary wavefields, differ by several orders of magnitude, and the waveform of the stained wavefield may be greatly distorted. We have developed a generalized staining algorithm (GSA) to achieve amplitude preservation in the stained wavefield. The real wavefield and the stained wavefield propagate in the same velocity model. A source wavelet is used as the source of the real wavefield; however, the real wavefield is extracted from the stained area as the source of the stained wavefield. The GSA maintains some properties of the original staining algorithm. The stained wavefield is synchronized with the real wavefield, and it contains only information relevant to the target region. By imaging with the stained wavefield, we obtain higher S/Ns in images of target structures. The most significant advantage of our method is the amplitude preservation of the stained wavefield, which means that this method could potentially be used in quantitative illumination analysis and velocity model building. The GSA could be adopted easily for frequency-domain wavefield propagators and time-domain propagators. Furthermore, the GSA can generate any number of stained wavefields. Numerical experiments demonstrate these features of the GSA, and we apply this method in target-oriented modeling and imaging as well as obtaining amplitude-preserved stained wavefields and higher S/Ns in images of target structures.