Depositional Facies Controls on the Geomechanical Properties of the Middle Jurassic Tuwaiq Mountain Formation

The geomechanical properties of rocks are crucial for understanding reservoir behavior and variations in quality, particularly in complex carbonate systems. While various approaches, such as well logs and seismic data, have been employed to characterize these properties in carbonate formations, achieving accurate results from these proxies remains challenging. The Middle Jurassic Tuwaiq Mountain Formation (TMF) in Saudi Arabia is of significant importance for both conventional and unconventional hydrocarbon exploration. However, limited research exists on the influence of depositional facies on the geomechanical properties of the TMF and the resulting implications for reservoir quality and heterogeneity. Thus, this study examines the rock mechanical behavior, geochemical composition, petrophysical properties,lithofacies and their interrelationships within the TMF. In the study area, TMF consists of three principal depositional facies, which are bioclastic Wackstone, peloidal grainstoneand bioclastic-peloidal packstone. The maximum and minimum average values for uniaxial compressive strength (UCS), compressional and shear wave velocities measured were 148MPa and 34MPa; 5924m/s and 3307m/s; 3135m/s and 1861m/s, respectively. The average porosity values obtained are ranging from a minimum of 2.3% to a maximum of 19.2%. The highest value of the UCS were recorded from the bioclastic wackstone depositional facies with relatively high organic matter content and the peloidal grainstone shows the lowest UCS values. Generally, the results indicate that UCS correlates well with both depositional facies and porosity. This study provides an insight into the influence of depositional facies on the geomechanical properties of carbonate reservoirs, their implications for predicting reservoir quality and stability in the TMF and comparable analog formations. The findings contribute to a more comprehensive understanding of carbonate systems and provide valuable information for reservoir management and development strategies.