Portal de Periódicos da CAPES

Basement Tectonics of Saudi Arabia as Related to Oil Field Structures

1992; Springer Nature (Netherlands); Linguagem: Inglês

10.1007/978-94-011-2654-0_10

0928-267X

H. S. Edgell,

Hydrocarbon exploration and reservoir analysis

All the oil fields of Saudi Arabia are of the structural type and they all lie in the northeastern part of the country, including the Saudi offshore portion of the Persian Gulf. These oil field structures are mostly produced by extensional block faulting in the crystalline Precambrian basement along the predominantly N-S Arabian Trend which constitutes the 'old grain' of Arabia. This type of basement horst, which has been periodically reactivated, underlies the world's largest oil field, Ghawar, and other major oil fields, such as Khurais, Mazalij and Abu Jifan. The basement horst beneath Ghawar Anticline has been suggested by Aramco (1959), from a positive Bouguer gravity anomaly which practically mirrors the field, and more recently, in greater detail, by Barnes (1987). All Saudi Arabian offshore oil fields, and some near coastal fields, such as Abu Hadriya, Abqaiq and Dammam, are also produced by basement faulting which has cut the saliferous, Upper Precambrian Hormuz Series, triggering deep-seated salt diapirism. Consequently, Saudi Arabian offshore and coastal fields are denoted by distinctive negative gravity anomalies. Some of these oil fields are circular, such as Dammam, Abu Hadriyah and Karan, whereas others are elongated, due to salt wall diapirism, as in the case of Khafji, Kurayn, Jana and Jurayd. The latter oil fields all follow a NE to NNE trend believed to be due to left-lateral strike-slip faulting in the basement, as seen in Kuh-e Namak on the Iranian side of the Gulf. One large offshore oil field at Manifa trends NW - SE, paralleling the Persian Gulf and is due to right-lateral strike-slip faulting in the basement along the well-known Erythraean Trend (von Wissman et al. 1942). An undeveloped offshore oil field at Hasbah trends E-W, due to basement faulting in this direction. Some major, elongated offshore oil fields with negative gravity anomalies trend almost N-S along the Arabian Trend, including Berri and Qatif, as well as the nearby Bahrain and Dukhan fields. All the known oil fields of Saudi Arabia and its offshore are thus related to four major directions of basement faulting, namely N-S, NE-SW, NW-SE and E-W. The major fault trend is the N-S Arabian Trend which has produced repeated basement horsts and grabens due to extensional tectonics. In the Saudi offshore portion of the Persian Gulf, NE-SW, left-lateral strike-slip faulting of the basement is also important in forming oil-field structures. A major difference between Saudi Arabian onshore and offshore oil fields is that the former show strong positive gravity anomalies due to block uplift of basement, whereas the latter have pronounced negative anomalies due to deep-seated salt diapirism induced by faulting in the crystalline basement. Detailed analysis of the potential field of gravity in the oil-field areas of Saudi Arabia, both offshore and onshore, substantiates these major basement-fault directions and shows the marked coincidence of oil-field outlines with large basement-induced gravity anomalies. The regmatic shear pattern of basement faulting is also clearly shown by mapping the second derivative of the potential field of gravity.