The Ordovician–Silurian Petroleum System of the Risha Filed, Eastern Jordan: A Comprehensive Review

The Ordovician–Silurian succession of eastern Jordan records a critical phase of geological, climatic, and tectonic evolution that shaped one of the most important Paleozoic petroleum systems within the Arabian Plate. This review integrates stratigraphic, sedimentological, and geochemical data from both outcrop and subsurface sections in the Risha region, emphasizing their significance for petroleum system development. The succession captures the transition from shallow-marine sandstones of the Risha and Dubeidib formations, through the Hirnantian glacial deposits, to the overlying organic-rich shales of the Mudawwara Formation. Together, these units constitute a complete petroleum system, with the post-glacial Silurian “hot shales” acting as the principal source rocks and the underlying glacial and periglacial sandstones serving as effective reservoirs. The vertical and lateral facies variations reflect the dynamic interplay between global glaciation, eustatic sea-level fluctuations, and regional tectonic reactivation along the northeastern margin of Gondwana during the Early Paleozoic. Organic geochemical evidence indicates that the Silurian shales attained thermal maturity under moderate to high geothermal gradients, generating hydrocarbons that migrated into the underlying porous sandstones. The integrated geological and geochemical framework highlights the high petroleum potential of the Ordovician–Silurian system in eastern Jordan, particularly within the Risha Field, which remains one of the most promising Paleozoic gas provinces in the region.