A Cepstral Technique for Unmasking Vital Sub-Seismic Stratigraphic Details Embedded in Dense 3D Seismic Data from Niger Delta (Published)
Seismic visibility is enhanced through the change of the seismic data outlook from the standard amplitude measurement to a new domain in order separate fact from artifact in seismic processing and interpretation. General seismic data interpretation involves direct fault and horizon mapping, sequence stratigraphy and seismic modeling to produce structural, stratigraphic and reservoir maps for the delineation, exploration and production of hydrocarbon in oil fields. These methods operate on stacked and migrated data and without adequate calibration. Besides, final stacks are inadequately displayed, processing is coarse and in time domain. Actual hydrocarbon entrapments are rarely detailed well enough to permit reliable location of wells from these studies alone owing to noise. This paper presents the results of the application of Cepstral transform (CT) in the interpretation of the 3D seismic data in the Niger Delta. The aim of the study was to develop a robust technique for mapping subtle stratigraphic units which are usually masked during normal data interpretation using Cepstral algorithm. The Cepstrum is the Fourier transform of the log of the spectrum of the data. The transform filters the field data recorded in time domain, and recovers lost sub-seismic geologic information in quefrency domain. Cepstral domain analysis separates source and transmission path effects. The algorithm is based on fast Fourier transform technique and was developed within Matlab software. The results of the Cepstral decomposition yielded gamnitude, saphe and quefrency maps of the reservoir and revealed sub-seismic faults, differences in lithology and better reservoir delineation and delimitation.
Citation: Orji, O.M., and Ofuyah, W.N. (2023) A Cepstral Technique for Unmasking Vital Sub-Seismic Stratigraphic Details Embedded in Dense 3D Seismic Data from Niger Delta, British Journal of Earth Sciences Research, 11 (1), 1-15
Keywords: Cepstrum, Fourier transform, Gamnitude, Hilbert transform, Homomorphic, Kepstrum, Quefrency, Saphe
A Cepstral Technique for Unmasking Vital Sub-Seismic Stratigraphic Details Embedded in Dense 3D Seismic Data from Niger Delta (Published)
Seismic visibility is enhanced through the change of the seismic data outlook from the standard amplitude measurement to a new domain in order separate fact from artifact in seismic processing and interpretation. General seismic data interpretation involves direct fault and horizon mapping, sequence stratigraphy and seismic modeling to produce structural, stratigraphic and reservoir maps for the delineation, exploration and production of hydrocarbon in oil fields. These methods operate on stacked and migrated data and without adequate calibration. Besides, final stacks are inadequately displayed, processing is coarse and in time domain. Actual hydrocarbon entrapments are rarely detailed well enough to permit reliable location of wells from these studies alone owing to noise. This paper presents the results of the application of Cepstral transform (CT) in the interpretation of the 3D seismic data in the Niger Delta. The aim of the study was to develop a robust technique for mapping subtle stratigraphic units which are usually masked during normal data interpretation using Cepstral algorithm. The Cepstrum is the Fourier transform of the log of the spectrum of the data. The transform filters the field data recorded in time domain, and recovers lost sub-seismic geologic information in quefrency domain. Cepstral domain analysis separates source and transmission path effects. The algorithm is based on fast Fourier transform technique and was developed within Matlab software. The results of the Cepstral decomposition yielded gamnitude, saphe and quefrency maps of the reservoir and revealed sub-seismic faults, differences in lithology and better reservoir delineation and delimitation.
Keywords: Cepstrum, Fourier transform, Gamnitude, Hilbert transform, Homomorphic, Kepstrum, Quefrency, Saphe
The Application of Edge Detection Techniques to Model and 3D Field Data Using Seismic Semblance and Cepstral Decomposition (Published)
Faults are critical to the accumulation of hydrocarbon and manifest themselves asabrupt, gradual or gentle changes of seismic amplitude. However reliable hydrocarbon entrapment in the presence of numerous subtlesub-parallel faults and their identification with computer–based algorithm is a major challenge.Fault detection technologies have proven to be important tools for seismic interpretation. Traditionally, edge detection techniques such as coherency algorithms, derivative methods, semblance,etcin time domain are employed in evaluating faulted hydrocarbon prospects by examining trace to trace similarity in data. These are inherently noisy. In frequency domain,spectral decomposition, requiring the use of a time window e.g. Fourier transform (FT),Hilbert transform(HT),Maximum entropy(ME),etc are used to unmask subtle events. However, these have high sensitivity to noise, weak frequency resolution arising from applied windows, and computational truncation, and are therefore unreliable. This has led to the need for improved techniques. We present the results of the application of amplitude-derived Semblance and Cepstral decomposition to model and 3D field data from the Niger Delta. The Semblance measures localized similarity while the Cepstrum is the Fourier transform of the log of the spectrum of the data and transforms the data from frequency to Quefrency domain. The attributes provide new improved information on the seal risk of hydrocarbon prospect. Our algorithm is based on fast Fourier transform convolution techniques. It was developed from basics and outside oil-industry interpretational platforms using standard processing routine such as Matlab,Gnuplot, Surfer. The results of the algorithm, when implemented on both oil-industry IHS Kingdom Advanced and general platforms were comparable and convincing. The Cepstral decomposition of the thin bed reservoir revealed subtle sub-parallel faults and provided an enhanced level of evaluating the seal risk on prospect. This will facilitate improved reservoir production and performance.
Keywords: Cepstrum, Depobelt, Fourier transform, Homomorphic, Maximum Entropy, Semblance