Comparism of Discrete Fourier Transform and Short Time Fourier Transform in Mapping Stratigraphic Features In TMB Field, Niger Delta

Abstract

The research compares the Short Time Fourier Transform (STFT) and Discrete Fourier Transform (DFT) methods on seismic signal processing in mapping hidden stratigraphic features in the 3D seismic data. Seismic data volume, suites of well logs and checkshot data were used for this research. The software used for this research is MATLAB and Suffer-8 Software. An alternation of sand and shale lithology was delineated in the gamma ray logs. The reservoir window/interval ranging in depth from 6300ft – 6384ft, was converted to time using check shot and tied to the seismic data. The reservoir interval (sand - 2.440sec to 2.468sec) in the seismic data was then divided at an interval of 4ms and decomposed with the STFT and DFT. A total of 10 slices was obtained between the top of the sand interval (2.440 sec) and the base of the sand (2.468 sec). The original seismic magnitude and phase was plotted for the top sand (2.440 sec) and transformed using the DFT and STFT in MATHLAB Software determined the domain frequency in terms of seismic attributes, magnitude and frequency. The identified lithologies in the reservoir bandwidth across the field comprise sand and shale. The results revealed that the sands have low frequency while the shale has high frequency. It was observed that the amplitude decreased with depth which is an indication of changes in formation fluid and sequence boundary. From frequency maps (slices) at data sampling interval (4ms) over the reservoir window, the STFT approach gave a detailed lithology variation compared with DFT.

Publication Info:

Author: Ideozu, R.U. , Emujakporue, G.O. and Awolola, O.K.

Volume: 56

Issue: March

Published By: Journal of Mining and Geology, 2024-03-01