ABSTRACT The establishment of a robust, paleontologically defined chronostratigraphic framework coupled with detailed facies analysis of outcrops resulted in the development of a sequence stratigraphic model for the Miocene synrift of the Gulf of Suez. Application of this model, along with 3-D seismic, has had a major impact on the ability to recognize stratigraphic and subtle combination traps within this mature basin. Graphic correlation of paleontological data from wells and outcrops reveals that the Neogene section consists of at least eight biostratigraphic sequences (S 10 -S 80) separated by graphic terraces (T 00 -T 70) or geologic lacunae. Outcrop analysis of terraces T 00 to T 30 and their associated fossil assemblages indicates that they represent either regional regressive or transgressive events. The number of depositional sequences (those bounded by regressive erosional surfaces) is therefore less than the number of paleontologically defined sequences. Terraces T 00 and T 20 are sequence boundaries, and subsurface evidence suggests that T 40 is a condensed interval and that T 50 is an erosional unconformity (sequence boundary). Field observations of T 10 at Wadi Thal in the Sinai indicates that it consists of at least two ravinements and a condensed section within a narrow stratigraphic interval. Similarly, the T 30 lacuna associated with the Markha Anhydrite at Wadi Feiran is composed of several stacked flooding and regressive surfaces. These surfaces at both Wadi Thal and Wadi Feiran represent minor time breaks. These small lacunae cannot be individually resolved by graphic correlation, but their sum total within a thin rock (hiatal) interval is detectable. Despite limitations in resolution, graphic correlation of paleontological data was crucial for recognizing key surfaces and intervals that allowed us to decipher the sequence stratigraphy of the Miocene synrift section of the Gulf of Suez. A regional analysis of the Miocene outcrops exposed along the Sinai margin of the Gulf of Suez within this constrained chronostratigraphic framework resulted in a depositional model for these strata that integrates tectonic history and sedimentary response during rift initiation and clysmic phases of rift basin evolution. The rift initiation phase is recorded by deposition of the Nukhul Formation. Nukhul depositional facies include: continental alluvial valley fill, estuarine, tidal flat, tidal channel complexes, and shallow off-shore marine. The clysmic stage of rifting is recorded by deposition of relatively deep marine mudstones, basin-floor fan sandstones, and footwall-margin conglomeratic-talus cone and fan delta deposits of the Mheiherrat Formation. The later stages of the clysmic rift were documented in the channelized submarine fan, offshore marine, deltaic, lacustrine, and hypersaline lagoon/sabkha deposits of the Hawara, Asl, and Ayn Musa formations. The cessation of active rifting is recorded by open marine mudstones and delta front deposits of the Lagia and Ras Budran members of the Ayun Musa Formation. The depositional history of the Suez Rift from the Aquitanian through Langhian stages of the Miocene began with northerly flowing fluvial systems occupying the down-thrown portions of asymmetrical half grabens. Increased subsidence resulted in a relative sea level rise that flooded the half grabens forming elongate estuaries and ultimately shallow open-marine environments. Uplift of the rift shoulders and basin subsidence during the clysmic stage resulted in relatively deep marine conditions within the rift and initially sediment starvation. As sediment supply readapted to the new topography submarine fans were deposited on the basin floor. Continued extension resulted in crustal thinning and an isostatic uplift of the rift, shallowing of the detachment depth and increased rotation of the tilted fault blocks. Shallower water open and marginal marine deposits prograded into and filled in the more subtle rift. Within the subsurface of the Gulf of Suez, seismic data is generally poor because of energy attenuation by shallow evaporites, multiple reflections, and complex structure. These conditions make traditional seismic sequence stratigraphy techniques difficult to apply. However, the tectono-sequence stratigraphic model developed from outcrops and the paleontologically-defined chronostratigraphic framework provides tools that allow for better subsurface correlations by systematically mapping stratal geometries using sequence boundaries and flooding surfaces defined by high-resolution biostratigraphic data. The stratigraphic picture that emerges from application of these concepts creates a profound change in quantification of fault throws and recognition of stratigraphic and combination traps. In addition to revealing new plays, application of the tectono-stratigraphic model also results in a better understanding of reservoir geometry and distribution.

Abstract The Gulf of Suez Basin is a classic extensional rift basin of Miocene age, with a number of syn- and pre-rift hydrocarbon plays. Exploration started in 1886, targeting areas around documented oil seeps, and was highly successful. During the boom in offshore exploration in the 1950s and 1960s, a combination of diligent geology and serendipity resulted in the discovery of a number of giant fields whose reserves form a major part of some 10 billion barrels discovered to date. However, the pursuit of smaller fields, both structural and stratigraphic, has been hampered by the poor quality seismic data characteristic of the basin. The poor quality of the seismic data is due to the interbedded shales and evaporites of shallow post-rift Zeit and South Gharib formations that create massive reverberation and severe attenuation of the seismic signal. Incremental progress in imaging the deeper horizons, including the key pre-rift Nubia Sandstone reservoir, has been achieved through low frequency enhancement and 3D seismic data acquisition. However it is still common for exploration and development wells to miss the Nubia objective due to the poor imaging and consequent misinterpretation of the seismic data. Exploration is now directed towards the smaller targets and subtle plays of the Gulf of Suez. To improve seismic imaging the focus has been on improved acquisition, with 3D ocean-bottom cable seismic data. This has the advantages of reduced multiple energy, higher fold and a broader bandwidth over streamer 3D data. Combined with detailed models of the tectonically controlled sedimentation that characterizes the syn-rift section, this has allowed the development of a re-invigorated exploration programme.

Abstract Since 1886 when the first oil was discovered and subsequently produced in the Middle East on Gemsa Peninsula, the Gulf of Suez has challenged the imaginations of geologists and continues to do so. The Gulf of Suez stretches over 300 km between the city of Suez and Ras Mohamed (Figures 1–3). The modern sea inundates only one-third of the geologic graben feature between the Sinai basement uplift and the Eastern Desert mountains. For simplicity, the whole graben system onshore and offshore is referred to as Gulf of Suez or "Clysmic Gulf" ("Clysma" being the Roman name of Suez) (Hume, 1921; Heybroek, 1965). The water body of the Gulf of Suez is rather shallow with a water depth of meters. Only in the southern part off Ras Mohamed does a deeper trench enter the gulf from the Red Sea. We define the southern end of the gulf as the line from Ras Mohamed to Shadwan Island and Hurghada. This line follows approximately a 200-m water-depth contour, where the Red Sea begins. The Gulf of Suez is the northern extension of the 2000-km-long Red Sea rift system, which is a Cenozoic structure slicing through the once-continuous Arabo-African craton. Geologically, the Gulf of Suez is a complex graben/half-graben system located between two basement uplifts—the Sinai and the Eastern Desert mountains. The graben cuts through older structural trends having ages from Precambrian to Eocene. The structure of the Gulf of Suez is dominated by normal faults and tilted fault blocks, which were formed after the Oligocene, mainly during Miocene time. The axial portion of the gulf underwent the most subsidence and contains the thickest deposits of lower Miocene sediments and middle/upper Miocene evaporites. In contrast to the Red Sea graben system, where motion is presently occurring along its entire length, the Gulf of Suez experienced extension primarily during Miocene time.

Abstract Ramadan field covers some 2850 ac (11.5 km 2 ; 4.5 mi 2 ) in the offshore, central province of the Gulf of Suez basin, some 174 km (108 mi) to the southeast from Suez City (Figure 1). The field is estimated to contain several hundred million barrels of oil as ultimate recoverable reserves, making it the fourth largest oil field in Egypt. The field is located on a gulf parallel (clysmic trending) tilted fault block system, generated during two pulses of rifting. Within the same area, and situated on similar structures, are the July and El-Morgan oil fields which, together with Ramadan field, account for over 39% of the oil reserves in Egypt. The field is operated by the Gulf of Suez Petroleum Company (GUPCO), which is a joint venture between the Egyptian General Petroleum Corporation (EGPC) and AMOCO Egypt Oil Company (a subsidiary of AMOCO Production Company).