Linking the sedimentary cyclicity with mechanical and physical properties of limestone and marl rocks, Dam Formation, Eastern Saudi Arabia: Implications for hydrocarbon exploration and reservoir development

This study aims to link the cyclicity with the mechanical and physical properties of limestone and marl rocks, using the Dam Formation in eastern Saudi Arabia as a case study. In this work, the Dam Formation sediments from five outcrop sections are investigated using detailed petrography, scanning electron microscope, X-ray diffraction, and petrographic image analysis software tool. Additionally, the physical and mechanical properties have been determined for marl and limestone samples. The study revealed that the emergence cycles result in the deposition of clastic sediments, in contrast to the submergence cycle, which leads to the deposition of carbonates. The dominant pore types, such as intercrystalline, micropores, mouldic, and vuggy, play an important role in the variation of mechanical and physical properties of the Dam Formation carbonate rocks. Secondary porosity produced by the dissolution of carbonate grains has a direct influence on mechanical properties. Physical measurements exhibit that limestone has a porosity of 10.5 and marl has a porosity of 5. Regarding physical properties prediction, our analysis shows that the emergence cycle commonly increases the chances of a decrease in matrix porosity and an increase in fractures, vugs, and cavern porosity, as well as increasing the permeability of the carbonate in the Dam Formation. A combined analysis of sedimentological and diagenetic features indicates that the clastic or marly sequences have low porosity and high uniaxial compressive strength (UCS); conversely, the limestone rock has high porosity and low UCS values. Quartz has an impact on the mechanical properties of the Dam Formation and is a major control of rock strength in clastic sediments. The UCS in emergence cycles shows moderate to strong strength, and saturation results in a loss of strength. The loss of strength in water-saturated conditions during emergence cycles ranged from 8.54 to 23.91 , with a mean value of 13.39 . The values from submergence formation reveal a 9.72�36.84 decline, when the results of UCS of samples in dry settings are compared to all wet conditions. Various relationships and empirical equations linking and estimating the physical and mechanical properties of the emergence and submergence sedimentary cycles have been developed, which can assist in subsurface reservoir modeling in the absence of core measurements. The derived relationships and empirical equations can also be utilized as analogues for other marl-limestone successions in similar geological settings. © 2023