The U.S. Geological Survey (USGS) assessed the potential for undiscovered, technically recoverable conventional oil and gas resources within a composite total petroleum system (TPS) of the northern Arabian Peninsula (fig. 1). The formation of the composite TPS is related to the tectonic history of the northern and northeastern parts of the Arabian Peninsula (Beydoun and others, 1992; Al-Husseini, 2000; Brew and others, 2001; Fox and Ahlbrandt, 2002; Ruban and others, 2007; Soleimany and Sàbat, 2010; Mouthereau and others, 2012; Barrier and others, 2014; English and others, 2015; Saura and others, 2015; Abdulnaby and others, 2020). Ordovician glaciation covered much of Arabia and northern Africa, and as the glaciers melted, widespread channel systems formed that were subsequently filled with organic-rich Silurian marine source rocks. As Gondwana began to fragment in the late Permian to Late Triassic, rifting formed the northeast–southwest-trending Palmyride and Sinjar graben systems in which were deposited synrift Triassic organic-rich source rocks (Barrier and others, 2014). Passive margin subsidence along the eastern margin of Gondwana from Early Jurassic through Late Cretaceous resulted in extensive carbonate platforms and intraplatform basins in which several major source rocks were deposited, including organic-rich marls of the Jurassic Sargelu, Tuwaiq Mountain, Naokelekan, and Hanifa Formations, and the Cretaceous (Albian–Cenomanian) Kazhdumi Formation. Late Cretaceous transtension, possibly related to a mantle plume, formed the northwest–southeast-trending Euphrates graben system (Litak and others, 1998), which divided the once-continuous Palmyride and Sinjar grabens (fig. 1). Major source rocks in the Euphrates graben system are Upper Cretaceous synrift organic-rich shales (Litak and others, 1998).

The USGS defined a Paleozoic–Mesozoic Composite TPS encompassing petroleum generated from several source rocks deposited on the northern and eastern passive margins of Gondwana. The Silurian Qusaiba Formation has generated most of the oil and gas in the northern part of the Arabian Peninsula (Lüning and others, 2000; Konert and others, 2001; Barrier and others, 2014; Cantrell and others, 2014; İnan and others, 2017; Varol and Demirel, 2020). Along the eastern margin of the Arabian Peninsula, source rocks are organic-rich basinal carbonate platform marls of the Sargelu and Tuwaiq Mountain Formations, Naokelekan and Hanifa Formations, and Kazhdumi Formation (Beydoun and others, 1992; Opera and others, 2013; Barrier and others, 2014; Baniasad and others, 2017). Jurassic and Cretaceous marls are the most important source rocks in the eastern part of the Arabian Peninsula (Beydoun and others, 1992; Ziegler, 2001; Damoulianou and others, 2020; Alipour, 2022). Eight assessment units (AUs) were defined within the composite TPS and reflect the tectonic history and formation of source rocks, reservoir rocks, traps, and generation of oil and gas (fig. 1). The Mesopotamian Foredeep Reservoirs AU and Mesopotamian Basin Anticlines AU have basement-related structural traps related to the formation of the Zagros Fold Belt, with clastic and carbonate reservoirs, and major Jurassic and Cretaceous source rocks. The Palmyride Fold Belt Reservoirs AU and Sinjar Fold Belt Reservoirs AU have Triassic synrift source rocks and reservoirs within structural traps. The Euphrates Graben Reservoirs AU has Upper Cretaceous synrift source rocks and clastic reservoirs in structural traps. The Aleppo Platform Reservoirs AU, Southeast Turkey Thrust Belt Reservoirs AU, and Northern Arabia Paleozoic Reservoirs AU have Silurian Qusaiba source rocks that reached thermal maturity for gas generation. Each of the eight AUs was assessed for undiscovered conventional oil and gas resources. The assessment input data are summarized in table 1 and in Schenk (2025).

The USGS quantitatively assessed undiscovered conventional oil and gas resources in eight AUs in the northern Arabian Peninsula (table 2). The estimated mean resources are 5,086 million barrels of oil (MMBO), or 5.1 billion barrels of oil, with an F95–F5 range from 1,438 to 12,016 MMBO; 19,546 billion cubic feet of gas (BCFG), or 19.5 trillion cubic feet of gas, with an F95–F5 range from 6,941 to 41,349 BCFG; and 735 million barrels of natural gas liquids (MMBNGL), or 0.7 billion barrels, with an F95–F5 range from 281 to 1,460 MMBNGL.

Assessment results are also available at the USGS Energy Resources Program website, https://www.usgs.gov/programs/energy-resources-program.

Christopher J. Schenk, Tracey J. Mercier, Phuong A. Le, Andrea D. Cicero, Ronald M. Drake II, Sarah E. Gelman, Jane S. Hearon, Benjamin G. Johnson, Jenny H. Lagesse, Heidi M. Leathers-Miller, and Kira K. Timm