1. Tanta University
Faculty of Science
Department of Geology
Submitted by
Mohamed Mahmoud Ahmed El-shora
Supervised by
Prof. Dr. Hamza Khalil

3. Chapter I:
Introduction
CHAPTER II:
Reservoir characterization of
the Gombe sandstone, southern Chad
basin Nigeria
CHAPTER IV:
Abu Gharadig Field Abu
Gharadig Basin, Egypt

4. is a clastic sedimentary rock composed mainly of sand-sized minerals or
rock grains “quartz and/or feldspar” .
A permeable subsurface rock that contains petroleum.
Fragmental reservoir rocks.
• Sandstone
Chemical and biochemical reservoir rocks.
• Carbonate rocks “L.S – Dolomite”
Miscellaneous reservoir rocks.
• Include the Igneous and Metamorphic rocks

5. The two essential elements of reservoir rock :
Porosity
Permeability

7. Depth
Porosity

9. • The study area is
located within longitude
11° 45` E and 14° 45`E
and 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).

10. • Sediments are mainly continental, sparsely fossiliferous, poorly sorted,
and medium- to coarse grained, feldspathic sandstones called the Bima
Sandstone.
Younger
Chad formation
Kerri-Kerri formation
Gombe sandstone
Gongila formation
Older
Bima sandstone

11. (Fig 2.2) Stratigraphic successions in the Nigerian sector of the Chad basin in relation
to the Benue Trough (Obaje et al., 2006).

12. • 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.

13. • consists of loosely cemented, coarse to fine-grained sandstone
(cross bedded), massive claystone and siltstone; bands of
ironstone 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.

14. • 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).

15. • 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 and
Winston, 1987).

16. • consisting of medium to
coarse-grained, arkoses
and subarkoses,
interbedded with
dolomitic/ anhydritic
mudrocks.
• The Kareem reservoir is
divided into nine reservoir
zones (Fig. 3.5; Zones A to I
from top to bottom) which
can be correlated across
the entire field (Bentley
and Biller, 1990).
(Fig 3.5) - Reservoir zonation of the El Morgan Field and
typical wireline log response (Bentley and Biller, 1990).

17. • The sandstones are unconsolidated
• Porosities are commonly in the range 20-30% (Fig. 3.9).
• Permeability (<100 mD).

18. Figure 4.1 - Location of the Abu Gharadig Field and structural framework of the Abu Gharadig Basin,
Western Desert (modified from Khaled, 1999).

19. • 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 in
the south and southeast of the Abu Gharadig Basin.

20. • The Bahariya Formation has been subdivided into three informal units in
the Abu Gharadig Field, labeled “Upper Bahariya”, “Middle Bahariya”,
and “Lower Bahariya” (Kenawy, 1988) (Table 4.1).

21. • characterised by a cyclic alternation of deltaic flood-plain
sandstones, coastal sandstones and shales, and shallow marine
shales and limestones.

22. • Abu Roash Formation “G” Member,
is Cenomanian in age, and is
mainly composed of marine shale
with thin carbonates and
sandstones.
• Member “F” (Late Cenomanian) is
composed of massive bedded,
dolomitic, shelly wackestone, with
laminated bituminous wackestone
and microbioclastic mudstone (Fig.
4.3).
• The Abu Roash “E” Member is Late
Cenomanian to Turonian in age and
is composed of shale, limestone
and sandstone, deposited in a
shallow marine environment.
• The shales at the base of the
member are organic-rich and are
considered to be one of the source
rocks 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).

23. • The shallow marine
carbonates of the Turonian
Abu Roash “D” Member
(Fig. 4.3) contain minor
reserves of oil in the Abu
Gharadig Field (Table 4.2).
They are overlain by the
sands and shales of the
Abu Roash “C” Member
(Fig. 4.5), which comprises
two regressive cycles
separated by a regional
coal bed marker (Wasfi et
al., 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).

25. • 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.

26. • 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).

27. • 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 productive
in two wells (AG-5 and AG-22).

28. • 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)
• Permeability is relatively low, with an average of 8-10 mD
and a maximum of 58 mD.