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The Application of 3D Seismic Semblance for Faults and Stratigraphic Features Using Cepstral Decomposition

Alao, Olatunbosun A.1; Adepelumi, Adekunle A.*1; Ako, Bankole D.1; Ofuyah, William N.1
(1) Department of Geology, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria, Ile-Ife, Nigeria.

Faults are critical to the accumulation of hydrocarbon and manifest themselves as abrupt, gradual or gentle changes of seismic amplitude. However, an important element of entrapment is the presence of numerous subtle sub-parallel faults and their identification with computer-based algorithm is a major challenge. Traditionally, edge detection techniques such as derivative, coherence, semblance, etc attributes in time domain are employed in evaluating faulted hydrocarbon prospects by examining trace to trace similarity in data, in frequency domain, spectra decomposition, requiring the use of a time window e.g. fast Previous HitFourierNext Hit Previous HittransformNext Hit (FFT), Hilbert Previous HittransformNext Hit (HT), Maximum entropy (ME), etc are used to unmask subtle events. Prospects dependent on fault closure are considered more risky than anticlinal trap because of blurred understanding of the principles of fluid migration in the viscosity of faults. Fault closure traps are capable of providing large and excellent hydrocarbon accumulations. However, these have high sensitivity to noise, weak frequency resolution arising from applied windows, and computational truncation. We present the results of the application of Cepstral decomposition of seismic amplitude and amplitude-derived semblance data in the interpretation of 3D seismic data from the Niger Delta. The cepstrum is the Previous HitFourierNext Hit Previous HittransformNext Hit of the natural logarithm of the Previous HitFourierNext Hit Previous HittransformTop of the data and transforms the data from the frequency to quefrency domain, while the semblance measures localized similarities. The developed Cepstral-based algorithm provides new improved information on the seal risk of hydrocarbon prospect by revealing the presence of multiple sub-parallel faults that can increase probability of up-dip lateral seal for hydrocarbon traps. The practical relevance of this study is illustrated by means of cross section of trap creating multiple sub-parallel faults which provides a convincing image to guide exploration management at progressive state of fault analysis on projects.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California