Implementation of Coupled 3D Geomechanics and Pore Pressure Model in Field Development Optimization: A Case Study from Depleted Sand Reservoir Interbedded with Weak Shale Intervals, Safa Field, Egypt

Abstract

Abstract Safa Field is a newly established onshore oilfield located in the southern central region of the Gulf of Suez, Egypt. It features a complex Miocene stratigraphic reservoir known as the "Hawara Sandstone Formation," which is capped by thick layers of shale and carbonate that act as a cap rock. After 22 years of production, the field has begun to show signs of water-cutting. Significant depletion has occurred within the sandstone layers due to continuous production. As a result, the reservoir pressure has dropped from an initial 4,200 psi at 9,600 feet to approximately 2,200 psi. Initially, using high mud weight was not problematic when drilling the reservoir. However, with the significant drop in pressure, it has become impossible to drill through all formations as before. The shale formations require high mud weight to prevent collapse, while the sandstone layers need lower mud weight to avoid mud losses. This paper emphasizes the role of high-resolution 3D geomechanical modeling in optimizing well costs for the Safa Oil Field. By integrating geological, geophysical, petrophysical, reservoir pressure, and drilling data, the study introduced a new casing set and optimized mud weight design tailored to the current stress conditions following depletion. The revised mud weight calculations positively influenced the casing design for two new wells. Additionally, an extensive uniaxial compressive strength analysis was conducted on the reservoir, resulting in the development of a new unconfined compressive strength equation. This equation, derived from an empirical relationship with total porosity, helped to reduce uncertainties in calculations for the reservoir section.