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Tanta University

Faculty of Science

Department of Geology

Submitted by

Mohamed Mahmoud Ahmed El-shora

Supervised by

Prof. Dr. Hamza Khalil

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Chapter I:Introduction

CHAPTER IV:Abu Gharadig Field Abu

Gharadig Basin, Egypt

CHAPTER II:Reservoir characterization of

the Gombe sandstone, southern Chadbasin Nigeria

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is a clastic sedimentary rock composed mainly of sand-sized minerals orrock grains quartz and/or feldspar .

A permeable subsurface rock that contains petroleum.

Sandstone

Fragmental reservoir rocks.

Carbonate rocks L.S Dolomite

Chemical and biochemical reservoir rocks.

Include the Igneous and Metamorphic rocks

Miscellaneous reservoir rocks.

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The two essential elements of reservoir rock :

Porosity

Permeability

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Depth

Porosity

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The study area is

located within longitude

11 45` E and 14 45`Eand latitude 9 30`N

and 13 40`N.

(Fig 2.1) Geologic map of Nigeria showing the inland basins

and the Nigerian sector of Chad basin (Obaje et al., 2006).

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Sediments are mainly continental, sparsely fossiliferous, poorly sorted,

and medium- to coarse grained, feldspathic sandstones called the BimaSandstone.

Older

Bima sandstone

Gongila formation

Gombe sandstone

Kerri-Kerri formation

Younger

Chad formation

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(Fig 2.2) Stratigraphic successions in the Nigerian sector of the Chad basin in relation

to the Benue Trough (Obaje et al., 2006).

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coarse feldspathic and cross-bedded sandstones.

It has been dated Albian.

consists of sequence of sandstones, clays, shales and limestone

layers.

Early Turonian age to the formation.

a sequence of sandstone, siltstone and shale.

The macrofauna is limited .Shell- BP palynologists dated the coal

late Senonian - Maastrichtian.

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consists of loosely cemented, coarse to fine-grained sandstone

(cross bedded), massive claystone and siltstone; bands ofironstone and conglomerate occur locally.

The coal in the formation has yielded palynomorphs on the basis

of which Shell-BP palynologists dated it Paleocene and later by

Adegoke et al. (1986).

a succession of yellow and grey clay, fine- to coarse-grained sand

with intercalations of sandy clay and diatomites.

its age is range from Pliocene to Pleistocene.

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The El Morgan Field is

located in the southern

sector of the Gulf of

Suez

(Fig 3.1) - Location of the El Morgan Field (Alsharhan and Salah, 1995).

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The El Morgan Field reservoirs are Lower to Middle Miocene

in age.

90% of production occurs in the Middle Miocene Kareem

Formation; minor production comes from the overlying

Belayim Formation; and minor reserves are contained within

the Lower Miocene Nukhul Formation (LaChance andWinston, 1987).

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The sandstones are unconsolidated Porosities are commonly in the range 20-30% (Fig. 3.9).

Permeability(

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Figure 4.1 - Location of the Abu Gharadig Field and structural framework of the Abu Gharadig Basin,

Western Desert (modified from Khaled, 1999).

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Kharita Formation is a series of sandstone bodies contain gas

in some wells of the Abu Gharadig Field .

The Kharita Formation is followed by the shallow marine to

coastal shales and fluvio-deltaic sandstones of the

Cenomanian Bahariya Formation, which is very sand-rich inthe south and southeast of the Abu Gharadig Basin.

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The Bahariya Formation has been subdivided into three informal units inthe Abu Gharadig Field, labeled Upper Bahariya, Middle Bahariya,and Lower Bahariya (Kenawy, 1988) (Table 4.1).

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characterised by a cyclic alternation of deltaic flood-plain

sandstones, coastal sandstones and shales, and shallow marine

shales and limestones.

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Abu Roash Formation G Member,is Cenomanian in age, and ismainly composed of marine shalewith thin carbonates andsandstones.

Member F (Late Cenomanian) iscomposed of massive bedded,dolomitic, shelly wackestone, withlaminated bituminous wackestoneand microbioclastic mudstone (Fig.4.3).

The Abu Roash E Member is LateCenomanian to Turonian in age andis composed of shale, limestoneand sandstone, deposited in ashallow marine environment.

The shales at the base of the

member are organic-rich and areconsidered to be one of the sourcerocks for the oil in the field(Khaled, 1999).

Figure 4.3 - Interpreted Sonic Log of typical Abu

Roash D, E and F Members (Bayoumi, 1996).

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The shallow marinecarbonates of the TuronianAbu Roash D Member

(Fig. 4.3) contain minorreserves of oil in the AbuGharadig Field (Table 4.2).They are overlain by thesands and shales of the

Abu Roash C Member(Fig. 4.5), which comprisestwo regressive cyclesseparated by a regionalcoal bed marker (Wasfi etal., 1986). It is subdivided

into four informal units,labeled 1 to 4

Figure 4.5 - Type lithological section of the Abu Roash C Member in well Abu

Gharadig-25 showing the breakdown into four lithogenetic units and their

environmental interpretation (Wasfi et al., 1986).

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The principal oil-bearing reservoirs in the Abu Gharadig Field are

the sandstones of the Abu Roash C and E Members.

The best reservoirs in the Bahariya Formation occur in the Lower

and Middle Bahariya Members.

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A) The Unit 2 sandstones of The Abu Roash C Member are fine-grained, slightly feldspathic and micaceous quartz arenites, with

quite a high percentage of heavy minerals, which gives

anomalously high gamma-ray and density logs (Wasfi et al., 1986).

Average porosity 21%

permeability ranging from 130 to 150 mD (Table 4.1).

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B) Abu Roash E Member, which has a reported average

porosity of 16% and an average permeability of 40 to 500 mD

(EGPC, 1992) (Table 4.1).

C) The Abu Roash D Member is a minor 26 ft carbonate

reservoir in the Abu Gharadig Field, which is only productivein two wells (AG-5 and AG-22).

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A) Upper Bahariya Member have low porosity and

permeability, and are not classed as good reservoirs

B) The Middle and Lower Bahariya sandstones are better,

thicker, and more extensive reservoirs, and represent 23% of

the total thickness.

Average porosity ranges between 2 and 19% (Kenawy, 1988)

Permeabilityis relatively low, with an average of 8-10 mD

and a maximum of 58 mD.

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