The Paleocene Shammar Reservoir: Explore a Sub-Seismic Stratigraphic Trap to Turn an Invisible Thin Sandstone into a Robust Low UTC Opportunity in North Oman

Approximately a decade ago, Shammar play was discovered in the northwest of the PDO concession Block-6 which was believed to be a strong top seal for the locally sub-cropping Cretaceous Shuaiba Formation reservoirs. The commercial rates of oil production from the Shammar developed fields and its low UTC characteristic made the play very attractive to expand its regional understanding and extend the exploration activities to other areas. Therefore, a comprehensive regional evaluation conducted around the recent Shammar discoveries and in underexplored segments, delivered a robust regional geological model, which led to a new drilling campaign resulted in discovery of two fields in North Oman in 2024. Despite the resounding success, there are plenty of challenges associated with exploring the stratigraphically trapped thin sandstones of base Shammar including: sub-seismic nature and lack of acoustic impedance control, prediction of reservoir occurrence, thickness, lateral distribution and extension and well geo-steering. In addition to the multi-disciplinary integration of all data including sedimentology (cuttings, SWS and conventional core), stratigraphy, petrophysics, seismic data, wells and geological models, the key enabler for the exploration success in the recent Shammar discoveries was the introduction of horizontal drilling at Shammar level. Two wells were geosteered horizontally successfully, marked as the first exploration Shammar horizontal wells and led to two new discoveries. Shammar accommodation and reservoir thicknesses heterogeneities are well known to be unpredictable. Horizontal drilling was utilized to de-risk additional subsurface points 800-1000m away from the main hole, which reduced the uncertainties and helped to understand the extension of the sand fairway. As the company continues to focus on resilient and attractive projects, the Shammar as shallow clastic play will continue to play an important role in sustaining exploration and development activities. Building on the success of this stratigraphic play concept, a Shammar play regional evaluation is ongoing to identify new concepts and leads. These volumes will support the exploration drilling plans in the upcoming 2-3 years. The concept is also being investigated over other areas where seismic acquisition or processing is underway. These will further contribute to the future business opportunities for the company and the Sultanate of Oman. The remaining Shammar prospectivity in North Oman represents a high-risk but potentially high-reward exploration target, given its location in an underexplored area. With the need for multiple wells, operational efficiency is a key to minimize financial exposure, especially when considering the unpredictability of the play.