Integrated Prospect Evaluation and Characterization Using Pre-Stack Seismic Data, Mansoura Area, onshore Nile Delta, Egypt

Abstract

In 2003, an aggressive drilling program started in Mansoura area in the onshore Nile Delta, with high success ratio. The program benefited from the direct hydrocarbon indicators provided by the post stack seismic data. After proving hydrocarbon presence in the field many reservoirs explored, however some challenges appeared lately. The most important challenges are the lithology and fluid discrimination due to the shale behavior, furthermore, the delineation of different reservoir properties like clay content, water saturation, and porosity proved to be challenging. Analysis of pre-stack seismic data for different reservoir properties prediction is commonly used for reservoir characterization. To enhance pre-stack seismic data quality some seismic gathers preconditioning flowcharts have been applied on the pre-stack data. The wavelet spectral analysis has been performed after conditioning the data then different techniques like the AVO simultaneous inversion, AVO analysis and density inversion have been applied on both west Dikirnis and west Khilala fields. Building rock physics model was carried out in the onshore Nile Delta to link the elastic properties and the reservoir properties. The model implemented in the unexplored areas within the concession to minimize the drilling risk of the delineated prospects. The rock physics model built in the area of study helped significantly to discriminate between wet sand, shale and gas sands. The middle and late Messinian are typically sand rich sections with excellent reservoir quality encountered in the drilled wells within both fields. Different reservoir properties predicted using the advanced inversion techniques in addition to the well data showing strong correlation at the well locations. The reliability of the far and ultra-far seismic data was encouraging. The cross-plot of the acoustic impedance versus shear impedance represents a useful technique in the onshore Nile Delta for sand and shale discrimination. Using Elastic impedance logs we can discriminate the water bearing sand, hydrocarbon sand and shale especially at the ultra-far angle.