Although the Partitioned Zone (PZ) between Saudi Arabia and Kuwait has been a prolific producer for over sixty years, significant resource potential remains in underexplored stratigraphic intervals. The Upper Cretaceous Hartha Formation is one of these opportunities. The Hartha interval has been penetrated by numerous wells targeting the deeper section in PZ, and although hydrocarbon presence has been observed in the Hartha, the play has not been fully characterized prior to this study.
Stratigraphic studies using core and well data concluded that the Hartha was deposited on a broad, low-angle carbonate ramp setting that includes the outer ramp, middle ramp, ramp margin, and inner ramp environments. Gross Depositional Environment maps were constructed based on these interpretations and show an approximately N-S strike-oriented ramp, similar to the orientation of the present-day shoreline of the PZ. Reactivation of basement highs during the Late Cretaceous influenced Hartha deposition, with high-energy grainstones deposited over and around these structural highs having the best potential for reservoir development.
Seismic interpretation was performed on recently acquired PZ 3D data to map key surfaces in the Hartha to Ahmadi section. The Hartha interval thins over structural highs and is significantly eroded by the pre-Hartha and pre-Aruma unconformities. This paleo-high structural trend in western PZ is also where the ramp margin grainstone fairway had developed and has been interpreted to contain the best reservoirs. Prospective areas are primarily structural closures over these highs inside the ramp margin fairway with stratigraphic facies changes to non-reservoir facies defining the lateral extent of the trap.