Geophysical 3D-static reservoir and basin modeling of a Jurassic estuarine system (JG-Oilfield, Abu Gharadig basin, Egypt)

Inadequate delineation of reservoir-heterogeneities, along with charge-timing confirmation, can considerably mislead exploration-development phases of petroleum. Therefore, precisely depicting the reservoir-architecture is crucial for avoiding exploration failures. To this end, integrated approach of various facies analysis and modeling-related disciplines; e.g. seismic facies, and GR-log motifs; was applied, in this study, to develop a depositional-model capable of aiding in stochastically-mapping reservoir heterogeneity and quality of the Jurassic estuarine depositional-system at JG-Field. To overcome the issue of sparse well control and scarcity of promising discoveries from deep-buried intervals in the study area, stochastic 3D-geocellular reservoir modeling, constrained by seismic attribute analysis, was performed to render a lateral prediction of different facies constituting the Jurassic succession. Predicting organic maturities and retrieving past geologic processes controlled sedimentary basin evolution were also a matter of importance to confirm hydrocarbon-charging to reservoir intervals. Accordingly, 1D-basin model was established so as to complete the story of petroleum system analysis in the area. We utilized dataset of seismic, log, core, and thin-section data; and applied both object-based and pixel-based, SIS (Sequential Indicator-Simulation) and SGS (Sequential Gaussian-Simulation), stochastic modeling algorithms upon simulating rock and fluid properties. The results show that the Jurassic succession constitutes a third-order depositional sequence of fluvio-estuarine units, subdivided into five sedimentary faciesassociations. Fluvial and tidal-bar facies associations enrich medium-grained sandstones, deposited in subaerial and subaqueous conditions respectively, featuring significant reservoir quality. Given best reservoir-quality, and considerable thickness, the tidal sand-bars ought to catch attention of future development strategies and be considered for investigation in similar settings.

Automated summary

This study developed a depositional model for predicting reservoir heterogeneity and quality of the Jurassic estuarine depositional system using an integrated approach of facies analysis and modeling. Stochastic 3D geocellular reservoir modeling, constrained by seismic attribute analysis, was used to predict the lateral distribution of different facies. Predicting organic maturities and understanding sedimentary basin evolution were also important in confirming hydrocarbon charging to reservoir intervals.