8. Reservoir Characterization
Statistical AVO Modelling and Petrophysical Analysis over Moonstone 3 Well, Offshore Niger Delta, Nigeria
D. E. Falebita, M. A. Olorunniwo, G. K. Oghenah and A. A. Adepelumi
Department of Geology, Obafemi Awolowo University, Nigeria.
Abstract
Statistical AVO modeling was performed over Mobil Nigeria Moonstone 3 well at a depth interval of 3500 to 3800 ft. AVO model equations were used to estimate the expected depth trends in rock properties. Rock properties extracted from the well data include density, porosity, sonic velocity, acoustic impedance, and reflection coefficient. The time-depth conversion was carried out using Normal Moveout velocities. The lithologies encountered were analyzed through the computation of their seismic parameters namely, P and S-wave velocities, P and S-impedance; P and S-wave reflection coefficients, AVO intercepts and Gradients. For normal incidence, AVO characteristics for shale has positive reflection coefficient and decreases with offset and a change in polarity occurs at far offset. For shaly-sand, it has negative reflection coefficient which increases with offset with no change in polarity. For water-sand and oil-sand, it has high reflection coefficient which decreases with offset and a change in polarity occurs at far offset. Also, for gas sand, it has positive reflection coefficient at normal incidence which decreases with offset with no change in polarity. Petrophysical analysis indicates that the porosity value is in the range of 25.7 - 47.5 percents. Permeability values are also excellent (332.88 - 51049.7 md). Hydrocarbon saturation is also high (40 - 95 percents). Evidence from bulk volume water suggests that the hydrocarbon is not moveable. However, the high permeability and porosity values, coupled with high hydrocarbon saturation and low water saturation suggest that the hydrocarbon is producible.
Last modified: Thu Apr 27 21:54:54 2006