AAPG Middle East Geoscience Technology Workshop, Integrated Emerging Exploration Concepts

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Integration of Seismic Techniques and Rock-Physics to Optimize Drilling Decisions in a Complex Geological Setting: A Red Sea Case Study

Abstract

The integration of two inverted seismic datasets from stacked and look-ahead VSP data has been used to efficiently plan and optimize a well operation. The method has proved to accurately estimate the depth of the reservoir, as well as the rock type in one of the delineation wells in a rift basin. The post-rift section of the basin is mainly composed of interbedded sands and shales with the presence of some evaporite streaks. Legacy well logs were used to identify different rock properties and to generate a pre-stack seismic inversion volume. The input data for the inversion were carefully conditioned and were also confirmed by the wells that were drilled later in that basin. The produced seismic inversion volume has a resolution higher than the resolution of the surface seismic, which has helped make better depth estimates for the pre-salt section. Due to the significant impedance contrast and optimized resolution, this high quality inversion data has helped to differentiate between the interbedded clastic and evaporite layers and greatly impacted the interpretation to map out the extents of the geobodies. In some areas, pre-stack data inversion data helped in identifying massive sand bodies in the syn-rift sedimentary section that is mainly composed of interbedded sands and shales. The acquisition of look-ahead VSP during the drilling was an important tool to calibrate the inversion volume and to optimize the well operation plans due to its higher resolution. The integration of the inverted VSP data with the inverted surface seismic data inversion resulted in better predictions of the depths and type of rocks. The use of these different geophysical tools have significantly added more confidence and value in the rock type prediction for facies distribution and drilling purposes.