Advanced Paleocurrent Analysis Over the Permo-Carboniferous, Methods to Reveal Its Complex Depositional History, Saudi Arabia

Abstract

Abstract The Permo-Carboniferous deposits in Saudi Arabia display a high-level of lateral and vertical heterogeneity resulting in a complex facies architecture. Such settings can be challenging to decipher using basic techniques that depend solely on openhole logs leading to inconsistent interpretation. The aim of this paper is to examine the role of local tectonics in the formation and alternation of subsurface depositional systems and associated hydrocarbon reservoirs in the area under investigation. This is accomplished through a multidisciplinary data integration approach involving core, borehole images, openhole logs, and seismic data. Specific objective includes reconstructing the paleogeography of the study area, which will grant better understanding of reservoir behavior on both vertical and lateral scales. The results of this paper suggest that deposition of the Permo-Carboniferous section at the study area is represented by low-sinuosity braided channels controlled by a preexisting Hercynian reactivated structure that served as a proxy of deposition. Detailed analysis of the paleocurrent data in the southern region of the field reveals three breaks in the sedimentary record. The basal events show variations in the paleocurrent orientations, suggesting deposition occurred over a preexisting terrain. The second event was characterized by a flat paleotopography associated with a period of tectonic stability and dominant unimodal NW sediment paleoflow. During this event, local lacustrine facies were developed in the SW part of the study area. The last event is marked by a SSW change in the paleocurrent flow and changes in lithofacies composition. It is postulated that the dramatic changes in paleocurrent directions are attributed to the reactivation of an earlier Hercynian paleostructure that could have supplied the area with new sediments. In contrast, the northern region of the field displays a consistent southerly paleocurrent flow, suggesting that the northern region was tectonically stable. This work reveals, for the first time, in detail the interaction between sedimentation and tectonism over the Permo- Carboniferous section in the study area. Such an approach can be adopted in other fields, ultimately leading to a systematic paleogeographic reconstruction mosaic of the region.