U.S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY
The Red Sea Basin Province: Sudr-Nubia(!) and Maqna(!) Petroleum Systems¹
Sandra J. Lindquist, Consultant to
U.S. Geological Survey, Denver, CO
World Energy Project
USGS Open-File Report 99-50-A
Three assessment units are delineated for the Sudr-Nubia(!) total petroleum system and two for the Maqna(!) petroleum system of the Red Sea Basin Province (Figure 3b and Figure 3c). For the purposes of resource assessment, a field-growth function utilized by the U.S. Minerals Management Service for U.S. offshore areas was deemed the most appropriate of those available to use for determination of ultimate recoverable reserves in the province.
In the Sudr-Nubia(!) total petroleum system (207101, Figure 3b), largely confined to the Gulf of Suez and completely within Egypt, an "established" assessment unit (Gulf of Suez Block-Fault Fairway, 20710101) encompasses most known production, where trap styles, seals, and reservoirs have been previously described. It is approximately 15,000 sq km in area. All risk is negligible, and infrastructure is well established. In the future, field sizes will be smaller than those presently discovered, and traps will be subtler structures or combination structural-stratigraphic types. Many new fields (mostly oil) are expected to be discovered in the next 30 years, with grown field sizes ranging between 1 and 1000 MMBOE ultimate recoverable.
A second "hypothetical" assessment unit of < 2000-sq-km area (Gulf of Suez Qaa Plain, 20710102) exists onshore to the east of 20710101 and has good physical accessibility. Source, trap, and efficient migration routes are riskier than 20710101. A few oil fields with a possible maximum of 500 MMBOE, grown ultimate recoverable reserves, might be found in the next 30 years.
A third "frontier" assessment unit with less established production than 20710101 (Southern Gulf of Suez, 20710103) at the deeper and hotter southern end of the Gulf of Suez and the northwestern Red Sea might additionally contain shallow salt-cored anticline traps and is likely to be more gas-prone than 20710101. It is nearly the same area as 20710101. Physical accessibility risk, due to greater water depths, is slightly increased from 20710101. Several dozen new fields are expected in the next 30 years with grown field sizes to a maximum of 600 MMBOE ultimate recoverable.
The Maqna(!) total petroleum system (207102, Figure 3c) includes all countries in the Red Sea Basin Province. It has one "frontier" assessment unit (Red Sea Coastal Block Faults, 20710201), more than 100,000 sq km in size, that includes all known production and contains block-faulted trapping configurations like those in the Gulf of Suez. This assessment unit includes coastal areas of the Red Sea and the southern Gulf of Suez – overlapping Sudr-Nubia(!) assessment unit 20710103 and parts of Sudr-Nubia(!) assessment units 20710101 and 20710102. Twelve producing fields in the Gulf of Suez and all six reported fields in the Red Sea are attributed to Maqna(!) hydrocarbons. Dozens of new fields are expected to be discovered in the next 30 years with grown sizes (ultimate recoverable) ranging from one to several hundred MMBOE for oil fields and from six to several thousand BCF for gas fields.
A second Maqna(!) assessment unit (Red Sea Salt Basin, 20710202) is more seaward to the first, is nearly three times as large, and is "hypothetical" because it contains only hydrocarbon shows. It is characterized by significant salt thickness and tectonism, greater water depths (but less than 1000 meters), greater depth to basement, and higher thermal gradients. Gas and oil are expected in traps created by salt flowage. A greater geologic risk exists for this Maqna(!) assessment unit than for the coastal block-fault Maqna(!) assessment unit. Grown minimum field sizes here will likely be at least 10 MMBO and more than 60 BCF. Based on an analogue of U.S. Gulf Coast onshore salt basins, it is expected that several dozen new oil and gas fields will be discovered in the next 30 years with maximum grown sizes of approximately several hundred MMBOE for oil fields and more than 2 TCF for gas fields.
The boundary between the coastal block faults (20710201) and the salt basin (20710202) Maqna(!) assessment units is based on Mitchell and others (1992) and Brown (1972).
The Gulf of Aqaba is considered too high risk to be quantitatively assessed in this effort because of its young age (<18 m.y.), low thermal gradient, significant water depth, and the unknown nature of possible source rocks, reservoir rocks and trapping configuration. But it is recognized that, approximately 200 km farther north along this transform system in the Dead Sea region, rapid subsidence of Cretaceous source rocks in the presence of low thermal gradients has generated recent hydrocarbons (< 3 Ma, Lewan and others, 1997).
The axial Red Sea rift – defined by water depths greater than 1000 meters and/or the probable presence of new sea floor as evidenced by magnetic anomalies – is not quantitatively assessed in this effort because of its young age (< 5 m.y.), high thermal gradient, concurrent volcanism, paucity of sedimentary section present, and improbability that Maqna-sourced hydrocarbons from the salt basins (20710202) migrated there and were trapped and preserved. It is possible that a hypothetical Pliocene total petroleum system with recent (< 5 Ma) generation exists within this hot, axial portion of the Red Sea rift, but reservoir rock and trap presence are questionable. This axial rift area is approximately 25% of the total Red Sea area.
Jurassic-sourced petroleum systems in the northernmost Gulf of Suez and the southernmost Red Sea are of lesser volumetric potential than Sudr-Nubia(!) and Maqna(!) and are not addressed in this evaluation and assessment.
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U.S. Geological Survey Open-File Report 99-50-A