Forward stratigraphic modelling (FSM) is an evolving technology for understanding the geology between wells for the purpose of exploration and field development. As opposed to the use of geostatistics, this process-based modeling approach uses physical equations for key controls on deposition, such as initial bathymetry, eustatic sea level change, subsidence rate, wave energy, and other environmental conditions. The output simulation is a 3D cellular model with properties like lithology, porosity, and water depth. FSM results do not honor the interpretation from the drilled wells. This means that the prediction accuracy from the generated model may not be high. The current process of calibrating forward stratigraphic models is time-consuming and tedious. In this paper, we propose an automated workflow to improve the accuracy of a forward stratigraphic model by automating its calibration to facies data from wells. For our case study, we use an initial stratigraphic model of the Hanifa and Arab-D in central Saudi Arabia. The modeling area covers 430 km by 370 km, the cell size is 10 km, and the simulation time step is 100,000 years. In the resulting model, cells are assigned to seven index facies based on their lithology, wave energy, and water depth. Initially, we conducted a sensitivity analysis to identify the environmental parameters with critical influence on the final model. Subsequently, we ran several simulations with varying values for these critical parameters. To measure the match between the different simulation models and the observed well facies, we used facies from 16 wells. The simulation run with the highest match was used as the best forward stratigraphic model. Uncertainty maps, based on superimposing several simulations, were generated to check which areas of the simulation are replicated more often than others, meaning they bear, relatively, the lowest uncertainty. This approach may be used to evaluate the risk of drilling new wells in specific locations, or to provide a measure of the uncertainty for subsequent reservoir simulations. In the future, we will use seismic facies and attributes, in addition to well data, for the model calibration.

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Tectonic analysis indicates a high possibility of tectonic escape (P. Tapponnier and others, 1982, Armijo, R and others, 1986) structures in central Saudi Arabia that could bear significant hydrocarbon exploration potential. This study aims to introduce a new tectonic model that explains several surface and subsurface newly mapped structures in central Saudi Arabia. Potential fields, seismic and surface geology data are integrated to accomplish this study. Basement terrane analysis of the Arabian shield and its eastern continuation beneath the sedimentary basin indicates the general north-south orientation with differences in width and composition. It shows that the maximum crust thickness is in the middle of the outcropping shield with a promontory extending 200 km toward east in subsurface (Central Arabian Arch) where Triassic (Khuff) marine carbonates overlay the basement directly. The crust shows gradual thinning eastward from this promontory till the offshore Arabian Gulf. Some terranes show wedging-out and others show narrowing against the eastern side of the basement outcrops. This pattern suggests the tectonic escape of the wedging out and narrowing terranes against the competent Afif terrane since the InfraCambrian accretion of Arabia. The terrane accretion occurred by westerly driven terranes collided against the thick promontory of the Afif terrane causing dispersion toward south and north through east-west accommodation zones. Long segments of unusual east-west surface structures (faults and strike of strata) over the boundaries of the subsurface basement promontory from north and south are thought to be a dragging of the dispersed terrane fragments at the promontory boundaries. West of these east-west zones, deformation is concentrated at the north-south terranes with curved hard link transfer zones. This InfraCambrian tectonic setting is believed to have been reactivated during Phanerozoic tectonic phases to express its escape tectonics pattern further-up till outcrops. Re-distribution of the Phanerozoic stresses at that inherited basement fabric controlled the geometry of the sub-basins and their filling during extension phases. It controlled also the preferable locations of structural positive inversion during compression phases to form the fault related fold traps. This approach explains the diversity of structural styles in the sedimentary cover (compression, transpression, and transtension) that formed simultaneously during the Late Cretaceous compression but with different directions.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractTectonic analysis indicates a high possibility of tectonic escape (P. others, 1982, Armijo, R and others, 1986) structures in central Saudi Arabia that could bear significant hydrocarbon exploration potential. This study aims to introduce a new tectonic model that explains several surface and subsurface newly mapped structures in central Saudi Arabia. Potential fields, seismic and surface geology data are integrated to accomplish this study.Basement terrane analysis of the Arabian shield and its eastern continuation beneath the sedimentary basin indicates the general north-south orientation with differences in width and composition. It shows that the maximum crust thickness is in the middle of the outcropping shield with a promontory extending 200 km toward east in subsurface (Central Arabian Arch) where Triassic (Khuff) marine carbonates overlay the basement directly. The crust shows gradual thinning eastward from this promontory till the offshore Arabian Gulf. Some terranes show wedging-out and others show narrowing against the eastern side of the basement outcrops. This pattern suggests the tectonic escape of the wedging out and narrowing terranes against the competent Afif terrane since the InfraCambrian accretion of Arabia. The terrane accretion occurred by westerly driven terranes collided against the thick promontory of the Afif terrane causing dispersion toward south and north through east-west accommodation zones. Long segments of unusual east-west surface structures (faults and strike of strata) over the boundaries of the subsurface basement promontory from north and south are thought to be a dragging of the dispersed terrane fragments at the promontory boundaries. West of these east-west zones, deformation is concentrated at the north-south terranes with curved hard link transfer zones. This InfraCambrian tectonic setting is believed to have been reactivated during Phanerozoic tectonic phases to express its escape tectonics pattern further-up till outcrops. Re-distribution of the Phanerozoic stresses at that inherited basement fabric controlled the geometry of the sub-basins and their filling during extension phases. It controlled also the preferable locations of structural positive inversion during compression phases to form the fault related fold traps. This approach explains the diversity of structural styles in the sedimentary cover (compression, transpression, and transtension) that formed simultaneously during the Late Cretaceous compression but with different directions.