The relationship between lithological and geomechanical properties of tight carbonate rocks from Upper Jubaila and Arab-D Member outcrop analog, Central Saudi Arabia

The study investigates the relationships between lithofacies and geomechanical properties of Arab-D Member and Upper Jubaila Formation outcrops in central Saudi Arabia. This outcrop studied is stratigraphically equivalent to the Arab-D reservoir in the subsurface. The methods used consisted of integrated field sedimentological analyses and laboratory tests. These tests included analysis of petrographical thin sections, Schmidt Hammer, Point Load Index tensile strength tests, and ultrasonic wave velocity measurements. Several lithofacies types were revealed within Upper Jubaila Formation and the Arab-D Member which is deposited in the upper to lower slope to ramp crest and shallow lagoon paleoenvironments, respectively. Generally, the lithofacies showed moderate correlation between geomechanical properties, porosity and permeability. Consequently, three geomechanical units were recognized within the Arab-D and Jubaila Formation based on change and shift of geomechanical properties across the boundaries. The upper unit corresponds to the upper part of the Arab-D Member; the middle unit corresponds to the lower part of the Arab-D Member and the upper part (5 m) of Upper Jubaila Formation, while the lower unit corresponds to the lower part of Upper Jubaila Formation. These geomechanical units reflect the joint effects of lithofacies and stratigraphy, while the moderate correlation among parameters might be attributed to superimposed post-depositional weathering and diagenetic processes.