Successfully Engineered and Delivered a Highly Inhibitive Anti-Accretion Drilling Fluid System for Drilling Ancestral Nile Fill Well in the North Beni-Suef Area

Abstract Petrosilah, a joint venture between the Egyptian General Petroleum Corporation (EGPC) and IPR Lake Qarun Petroleum (IPR LQP)/Pharos Energy, holds a stake in the North Beni-Suef (NBS) exploration concession in Egypt's Western Desert. Drilling the Ancestral Nile Fill clastic deposits in offset wells west of the Nile has historically posed significant challenges due to borehole instability and highly reactive formations. These challenges have led to numerous drilling complications, including pack-off tendencies, tight holes, severe to complete losses, casing hang-ups, and mechanical sidetracks. Traditional approaches to mitigate these issues have relied on expensive mud additives, heavy mud weights, varying casing depths, conditioning trips, and continuous reaming. Although the Drilling with Casing (DwC) system has been utilized, it has inherent limitations. To address these challenges, Petrosilah, in collaboration with Baroid Drilling Fluids, developed a novel approach to optimize a cost-effective drilling fluid formulation that enhances wellbore stability while reducing the overall cost impact observed in previous Beni-Suef offset wells. The optimization process was divided into two key phases: planning and execution. The planning phase involved gathering and analyzing data, including sampling the Ancestral Nile Fill formation from offset wells at a sister company. These samples were assessed against various highly inhibitive fluids commonly used in the Egyptian Western Desert. Through rigorous laboratory analysis, particularly using linear swell meter results, a clear advantage emerged for a silicate-based fluid enriched with 3-5% v/v GEM GP, which was ultimately selected after evaluation against well objectives. In the execution phase, the selected silicate-based fluid demonstrated remarkable efficiency during field application, delivering best-in-class performance in the first two exploration wells, NBS-SW-1X and NBS SW-5X. This paper details the step-by-step process and methodologies employed in fluid selection, Ancestral Nile Fill formation analysis, and field observations, leading to the successful application of the silicate/GEM GP drilling fluid. This innovative approach effectively tackled previous drilling issues in the Beni-Suef wells’ intermediate sections, eliminating borehole instability and significantly reducing drilling costs. This work represents a substantial advancement in drilling practices for challenging environments.