Nile Delta(Tectonic setting, Stratigraphy and Petroleum

System) Prepared by : Ahmed El_Sayed Hamza

4th Geophysics 4/5/2016

Introduction :Delta is characterized by a triangular plain formed where the mouth of the river empties into a larger body of water

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*Tectonic setting:The general structural setting of the Delta area has been determined using both geophysical methods and well data.The main feature is the Nile Delta Hinge Zone, a flexure which affects pre-Miocene formations and is a set of the E-W normal faults with a big throw down to the north, controlling the origin of the Nile Delta.*Geologically, the greater Nile Delta region covers the following structural-sedimentary provinces :the South Delta Blockthe North Delta Basinthe Nile Conethe Levant Platform.

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*North of the Hinge Zone, large normal faults are the dominant structures. These gravity induced, ‘down-to-basin’ displacements occur along listric fault planes and have thick Neogene formations which mainly developed in open marine, deep-water facies .

* The offshore Delta is characterized by a thick subsidence-controlled sequence of Tertiary sediments.

* South of the Hinge Zone, asymmetric folds of the Syrian Arc Fold System extend along an arcuate trend from northern Sinai and the northern Gulf of Suez, through the southern part of the Delta and into the Western Desert.

*The basement in this southern area is relatively shallow and block faulting is more common.

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*Numerous fault systems exist in the upper basement surface and in overlying sediments.

*Fault systems composed of folded, Mesozoic platform carbonates which form a number of thin horst-and-graben fault blocks features oriented mainly in NE-SW and NW-SE directions.

*The South Delta Block is characterized by a gradual northward dip of the top of the Middle Eocene carbonates which is gently folded and dissected by approximately E-W normal faults

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*Stratigraphy:1-The Miocene sequence is summarized as follows:1. MOGHRA FORMATION (EARLY MIOCENE):consists of marine to fluvio–marine deposits (shale and sandstone).

2. SIDI SALEM FORMATION (MIDDLE MIOCENE):composed of mudstone with interbeds of marls, sandstones and siltstones.

3. ABU MADI FORMATION (LATE MIOCENE):composed of interbedded sandstones and mudstones, The depositional environment changes from fluvial to lagoonal with marine influence increasing upward.

2-The Plio- Pleistocene sequences are represented by the following formations:

1. KAFR EL SHEIKH FORMATION (EARLY–MIDDLE PLIOCENE):Kafr El Sheikh Formation consists of mudstone sequence with thin limestone and sandstone interbeds. This formation extends all over the Delta area.

2. EL WASTANI FORMATION (LATE PLIOCENE):El Wastani Formation consists of thick sand beds interbedded with thin clay beds which become thinner toward the top of the formation.

3. MIT GHAMR FORMATION (LATE PLIOCENE):Mit Ghamr Formation consists of thick layers of sand and pebbles which show clay interbeddings of limited thickness.

4. BILQAS FORMATION (HOLOCENE):is the top sedimentary cover of the Nile Delta province. It consists of sand interbedded with clay rich in pelecypod, gastropod and ostracod fragments. The clays contain many fragments of vegetal matter and peat deposits.

PETROLEUM SYSTEM:Source Rock:*Organic-rich shales from the Sidi Salem and the Kafr el Sheikh formations are well known source rocks.

* Potential source rocks are mainly associated with transgressive time stratigraphic shale sequences within the Lower and Middle Miocene and the Oligocene.

* The Nile Delta and Offshore region has become a major gas province with significant new discoveries, such as Port Fouad

Reservoir Rock: *The Abu Madi sandstones have consistently proved to be the best reservoirs in the Nile Delta, as they have a high porosity with an average of 21 %.

* Most of the proven reservoirs are related to Upper Miocene sands.

* some smaller quantities of oil have been found in Middle and Lower Miocene sandstones.

* The majority of fields produce from the Abu Madi Formation, which comprises a series of thick, cross-bedded sand bodies, interbedded with thin shales.

* Hydrocarbons have been encountered further down the sequence, in the Sidi Salem Formation - a mixed unit of shales with a few dolomitic marls and infrequent sandstone interbeds.

Traps and hydrocarbon migration:* Lenticular sand are present on gentle anticlines.

*However, other types of traps, typical of deltas in general can be visualized .

* The generation of gas and its condensate is thought to have occurred in relatively recent time , that is after the deposition of the Pliocene sequence .

* The pathway from the source rock to the reservoir was probably short

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REFERENCE:*Facts About the Ancient Egyptian Nile Delta Areaby DaVaun Sanders, Demand Media*https://community.dur.ac.uk/penelope.wilson/Delta/Delta.htm

*http://www.egas.com.eg/Corporate_Overview/Exploration.aspx*WELL EVALUATION CONFERENCE Dr Hamdi El Banbi