Structural and facies modeling of the Aptian Dahab Formation, Matruh Basin, northern Western Desert, Egypt

Abstract

This paper presents a comprehensive study of the structural geometry and tectonic evolution of the Aptian Dahab Formation in the Matruh Basin, Egypt, using high-quality 3D seismic and well data. It also details the methodologies used to develop precise 3D structural and facies models for the Dahab Formation in the study area, which elucidate the stratigraphic succession, depositional environments and facies, tectonic and eustatic influences on deposition, and the spatial distribution of the Dahab Formation.

Detailed well log correlations indicate the presence of normal faults, affecting the preservation of the upper part of the Dahab Formation in the boreholes. The study employs a 3D structural modeling workflow, integrating seismic and well data, structural cross-sections, and maps. Velocity modeling and depth conversion highlight the complex structural setting resulting from the impact of Late Cretaceous faulting and folding on the Aptian Dahab Formation.

Further, a 3D facies model was constructed, that incorporated upscaled well logs and variogram analysis. The results indicate that the lithological composition of the Dahab Formation in the study area is 38.4% shale, 28.96% siltstone, 15.35% sandstone, 12.36% limestone, and 4.92% dolostone. Hence, the facies model shows the dominance of shale facies, which increase towards the south, while siltstone and sandstone facies become more prevalent towards the north, likely sourced from that direction. Two cross sections were constructed that illustrate the lateral and vertical facies variations within the Dahab Formation, which thickens as it extends northwestward. Consequently, the facies distribution model of the Aptian Dahab Formation could serve as a global analogue for potential siliciclastic reservoirs deposited in a shallow water environment.