الملخص الإنجليزي
Oil and gas industry nowadays heads towards complex reservoirs. This study aimed at
predicting Upper Gharif channels in Central Oman by discriminating sand from shale.
Two main approaches were followed: a) establishing Rock Physics Modelling (RPM)
relationships via well data: Density- P-wave Velocity – Shear-wave Velocity (Rho-VpVs) and recognizing separate models for the reservoirs and non-reservoirs, and b)
advanced seismic attributes such as Spectral Decomposition (Fast Fourier Transform
(FT), Continuous Wavelet Transform (CWT), Shell Spectral Decomposition (SSD)) and
Artificial Neural Network (ANN)-based attributes. Density-P-wave Velocity (Rho (Vp))
relationship suggests that the Middle Gharif clastics differ from Upper and Lower Gharif.
This hints at the alteration in sediments source, mineralogy, depositional environment
and/or other geological factors. Density-Porosity (Rho (φ)) marks possible variant pore
types and factors (diagenetic, local facies changes for example) in Upper and Middle
Gharif. RPM scenarios concluded that Acoustic Impedance (AI) and synthetic seismic
trace suggest dimming features indicating Gharif sand bodies (high AI). Far Stack seismic
reflectivity at Θ=35o
is tested for sand-shale discrimination and showed dimming in
relation to Near Stack seismic reflectivity at Θ=0°. Advanced seismic attributes clearly
indicate the Upper Gharif channel belts (anastomosing) as dimming features running
mainly in E-W orientation in line with channel geological depositional model. For
example, Fast Fourier Transform (FT) map of 40Hz at 15ms below Upper Gharif event,
Artificial Neural Network (ANN)-based confidence map and Shell Spectral
Decomposition images extracted 5ms and 10ms below Upper Gharif event showed the
complex Gharif channel pattern in study area. Gamma Ray response character supports
the depositional environments interpretations i.e. fluvial point bar (ZL-25H1), flood plain
(FWRN-2H 2 and AFL-1H1) and a crevasse splay (HSR-3H1), which were interpreted
through the dimming and brightening features seen from the 40Hz FT (15ms below Upper
Gharif event).
