12. Imaging/Interpretation Frontiers
Overpressure Detection with Time-frequency Attribute
Ehsan Zabihi Naeini and Hamid Reza Siahkoohi
Institute of Geophysics, University of Tehran, Iran.
Abstract
Abnormal pressure, or pressures above or below hydrostatic pressure, occurs on all continents in a wide range of geological conditions. Various physical processes cause anomalous pressures in an underground fluid. The most commonly cited mechanisms for abnormal pressure generation in petroleum provinces are compaction disequilibrium and hydrocarbon generation including oil-to-gas cracking (Mann and Mackenzie, 1990; Luo and Vasseur, 1994). In young (Tertiary) deltaic sequences, compaction disequilibrium is the dominant cause of abnormal pressure. In older (pre-Tertiary) lithified rocks, hydrocarbon generation and tectonics are most often cited as the causes of overpressure (Law et al, 1998). Overpressure regime cause significant attenuation of seismic energy. Also some attenuation and velocity anisotropies are reported in literatures. In this study Instantaneous Dominant Frequency which is obtained from time-frequency map of wavelet transform is used to detect overpressure region. Wavelet transform has an optimum time-frequency resolution in comparison with short time fourier transform. Seismic data of a reservoir in south-west of Iran is used in this study. Overpressure is reported by geologists in Gachsaran horizon which is in agreement with the result of our attribute.
Last modified: Fri May 19 19:58:30 2006