From Plate Tectonics to Microbialites: An Integrated, Multi-Scale Reservoir Sweet Spotting Study to Optimize Well Design and Drilling Locations in Jurassic Carbonate Gas Fields, North Kuwait

In carbonate reservoirs, sweet-spots driving flow behaviour are controlled by the interplay of depositional, diagenetic, and structural-geomechanical processes (Cross & Burchette, 2024). Kuwait Oil Company's (KOC) development goal of ramping-up North Kuwait Jurassic gas production relies on high-graded drilling and completion design concepts targeting optimal reservoirs. We present a coherent, quantitative and cross-disciplinary subsurface workflow to define and delineate reservoir sweet-spots in tight gas reservoirs of the Jurassic Middle Marrat Formation. To identify growth targets we deployed a multi-scale approach leveraging Shell's in-house expertise in tectonics, structural and carbonate geology, petrophysics, and machine-learning along with state-of-the art tools to approach reservoir sweet-spotting from a new angle. Building on Shell's proprietary Paleo-Earth modelling platform, we combine plate kinematic and neo-tectonic models with subsurface observations on basin- and lithosphere scale to quantify the contributions of changing plate boundary configuration to the evolving in-plate stress field of the Arabian plate/Kuwait region. This allows us to spatio-temporally predict the stress field through geological time and evaluate the link between basement, fracture corridors, and inversion/reactivation. Decompaction and structural restoration techniques enabled mapping of paleo-closures, tilted contacts and computing cumulative strain. Sedimentological & diagenetic sweet-spots utilized core-based facies association interpretations that were converted to gross depositional environment maps and tied to their underlying structural inheritance. Traditional sedimentology was combined with core-based artificial intelligence (AI) algorithms and integrated with wireline-log and production data to identify depositional and diagenetic sweet-spots with high-permeability architectures. The sweet spots were found to be defined by back-barrier microbial build-ups and extensive lagoon-bound fine-crystalline dolomite layers. This study identified sweetspots that are now infill and appraisal drilling targets with the nature of the sweet-spots determining well-path and completion design. The decompaction work delineated paleocontacts and predicted the location of tilted hydrocarbon contacts away from well control for the next phase of appraisal drilling. Paleo-stress analysis high graded fractured areas for horizontal wells in low permeability zones. Initial results from Gotnia-aged stress reconstruction indicate significant changes in the stress field compared to present-day that shed light on the deformation history and impact of changing plate boundary configurations of the Afro-Arabian plate in the latest Jurassic. These models question whether classic ideas such as the "Hercynian", "Alpine 1" and "Alpine 2" deformation events can be used to fully explain the deformation and reactivation history of inversion structures in Arabian-plate carbonate reservoirs.