Evaluation of petroleum system elements and processes in the Risha gas field, eastern Jordan: A comprehensive study

The petroleum system in the Risha gas field, eastern Jordan, is not fully understood. The current study aims to evaluate source rocks, reservoirs, and seals within the basin by integrating 1D basin models and well logs together with geochemical and petrophysical data. Two effective source rocks are identified within the Paleozoic shale intervals, namely the Mudawwara and Dubeidib formations. The Mudawwara and Dubeidib formations with TOC values ranging from 0.51 to 6.75 wt%, which suggests poor to very good potential. The formations contain primarily Type III (gas-prone) and mixed Type II/III (oil/gas-prone) kerogen. The thickness of the Paleozoic sedimentary section increases to the east. In contrast, the thickness of the Mesozoic section increases to the west, and the entrapment area in the middle to the eastern part of the study area is characterized by the accumulation of petroleum in the Ordovician sandstone reservoirs. The Risha sandstone reservoir has an increased net pay thickness in east and southeast directions. The migration of hydrocarbons petroleum in the Risha gas field is strongly suggested as a direct primary migration from the source rock intervals within the Mudawwara and Dubeidib shales to the intercalated sandstone reservoirs of the Risah and Dubeidib formations. In addition, vertical migration along faults and up-dip migration to the middle and eastern parts of the study area are also suggested. The Risha-14 well represents the ideal petroleum system in eastern Jordan, as it encompasses all the key elements of petroleum generation and accumulation. The critical moment for the source rock is estimated to have occurred approximately 250 Ma ago. The effective shale source rocks of the Mudawwara Formation were deposited in the Early Silurian. They entered the main oil window in the Early Devonian (∼410 Ma ago), with significant gas generation occurring in the early Carboniferous (∼330 Ma ago). The Dubeidib Formation sandstone reservoir was deposited during the Ordovician (485-458 Ma ago). Structural traps formed during the Paleozoic (280-250 Ma ago), formed during the Hercynian Orogeny through rifting and compression phases were subsequently charged with petroleum through migration and accumulation.