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New Hydrocarbon Prospect Determenation via Subsurface and Petrophysical Evaluation of Rudeis Formation, Belayim Land Oil Field, Gulf of Suez, Egypt.
M. A. ABD ELHADY1, A.S.S. AHMED2, A.M.METWALY2
1 Geology Department, Faculty of Science, Al Azhar University. 2 Belayim Petroleum Company.
ABSTRACT
This present work aims to combines the formation evaluation of wireline well logs with subsurface geological model of the Rudeis Formation in Belayim Land Oil Field, Gulf of Suez. Results followed procedures to evaluate reservoir characteristics throughout the penetrated wells in this Formation. The subsurface geological investigations were accomplished by studying the stratigraphic, tectonic and structural settings, and the petrophysical evaluation was done by the computer processed interpretation that puss through the quantitative interpretation technique. Petrophysical studied, core log data and porosity permeability relationship that reflact the good reservoir quality which can delineate more fluids with high porosity. The study area has all criteria to make it of considerable hydrocarbon potential. It is characterized by having homogeneous lithological response relevant mainly to sandstone facies, the hydrocarbon generating source rock, seal rock, reservoir rock, with reasonable porosity and structure closure. As results of the present study, using the subsurface and petrophysical evaluation, the data of Rudeis Formation has one trend with excellent correction Coefficient (91 %). That reflects the good reservoir quality which can delineate more fluids with high porosity. As a result of the present study three location are proposed to be prospects in Rudeis formation, these location structurally are located within a three way dip closure that is very attractive place for hydrocarbon accumulation.
Keywords: Reservoir characterization, Belayim Land Oil field, Rudeis Formation.
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1-INTRODUCTION
The Gulf of Suez is one of the most important hydrocarbon province in Egypt. Belayim land oil field lies on the eastern side of the Gulf of Suez, one hundred and 65 kilometers southeast of the Suez City (Fig. 1). It has been subject to intensive exploration activities since the early last Century. The Rudeis reservoirs are present over most of the study area and represent about 20% of production potential in the Gulf of Suez. The Rudeis sandstone has produced oil from fields such as the Shoab Ali, East Zeit, Ashrafi, GH376, Amal, Asal, Belayim Marine, Belayim Land, Al Ayun, July, Kareem, Matarma, Sudr, Morgan, Kheir, and Umm El Yusr and has tested gas from the Felefel field.
2-METHODOLOGY
The present study is based mainly on the use of the available wireline logs of four wells namely (113-81,113-95,113-142 and 113-166 St) and seven 2D seismic lines distributed in the study area, as shown in Figure (1).
Figure (1): Location map of Belayim Land Oil Field. It shows the location of the selected wells
in the study area.
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Stratigraphic Setting
The lithostratigraphic sequence of the study area ranges from Cambrian to Recent. It can
be classified into two mega sequences; pre-rift and syn-rift (Fig. 2). The stratigraphic time and
rock units, determined by examinations of outcrop sections, subsurface cores, electric logs as
well as micro faunal studies from ditch samples and thin sections, were described by Sadek
(1959), EGPC Stratigraphic Committee (1964), Webster (1982), Sellwood and Netherwood
(1984), Salah (1989), Ayad and Stuart (1990), Gawthorpe, R. L. and Hurst, J. M., (1993),
Bosworth and Mc Clay (2001) and Abd El-Naby et al. (2009) and others.
The penetrated stratigraphic section of the study area (Fig.2) ranges in age from Lower
Miocene (Rudeis Formation) to the Pliocene (post Zeit).
.
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Figure (2): Stratigraphic section of the study area (after Anany 2008).
Stratigraphic correlation chart in figure (3), runs in the East-West direction hanged on
Top Rudeis Formation and connecting the studied wells, shows that the Rudeis Formation is
thick in the South Western part recording it’s maximum thickness 330 m at 113-81 well and
decreases towards the North Eastern part recording 51 m at 113-166 ST.
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Figure (3): Stratigraphic Correlation chart of the study area Rudeis Formation.
STRUCTURAL SETTING
The Gulf of Suez is dissected by a complex pattern of faults: N-S to NNE-SSW as well as
E-W trending normal faults at the rift borders and within the rift basin, and NE trending strike-
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slip faults crossing the Gulf basin (Abd El-Naby et al., 2009). The interaction of these major
fault systems resulted in a complex structural pattern consisting of numerous horsts and grabens
with variable relief and dimensions.
The Gulf of Suez is currently subdivided into three structural provinces according to their
structural setting and regional dip directions. (El Diasty and Peters, 2014)
The central province occupies the central part of the Gulf of Suez. The characteristic
feature of that province is the pre-Miocene shallow structures underlying the Miocene sediments.
These highs were subjected to severe erosion. The eroded Pre-Miocene sediments were
redeposited in the early troughs. The regional dip is north east. The main clysmic and Aqaba
trending throw toward the southeast and northwest respectively.
Structure Contour Map.
The structure contour map of Rudeis Formation in study area figure (4) shows that was affected by four fault trends (NW-SE,and NE-SW) Rudeis Formation and this trends shown in seismic sections figures( 5), the same structural trends. A set of normal faults forming a horst, graben and step fault block that are very convenient for oil accumulations.
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Figure (4):The structure contour map of Rudeis Formation.
N
A
A’
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Figure (5): Seismic Section passing through of the study area.
Delineation of the structure
To elucidate the above mention structure, the geologic cross section (fig 6) was constructed in direction NW-SE respectively, direction of faults, unconformity, deviation of dips, thinning and thickening are evident.
The geologic cross section fig 6 passes through 113-81 and 113-95 wells. This section is shows 4 normal faults cutting through studied wells of succession forming horst and step blocks in South East and North West Side, South east block is dipping toward east and North west block dipping toward west.
NW SE
N
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Figure (6): Geologic structural cross section.
The Isopach map of Rudeis Formation
The Isopach map of Rudeis Formation is presented in Figure 8. The Thickness in study
area ranges between 51 m in 113-166-ST well to 330 m in 113-95 well. It is clear that increases
towards the South West part of the study area, in the vicinity of 113-95 well. However, the
platform occurs in the northern part recording its minimum thickness.
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Figure (8): Isopach map of Rudeis formation.
Lithological Identification cross-plot
The neutron-density and the neutron-sonic cross-plots of Rudeis Formation in four wells except one well which have not a particular login figure 9. It is mainly characterized by the predominance of sandstone. It is also characterized by the presence of shale and dolomite as cement.
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37525
113-142
113-81
113-95
113-166(st)
124.00
330.00
215.00
51.00
829500 830000 830500 831000 831500 832000 832500 833000 833500
829500 830000 830500 831000 831500 832000 832500 833000 833500
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30.0040.0050.0060.0070.0080.0090.00100.00110.00120.00130.00140.00150.00160.00170.00180.00190.00200.00210.00220.00230.00240.00250.00260.00270.00280.00290.00300.00310.00320.00330.00340.00350.00360.00370.00380.00
True vertical thickness [m]
C.I.=10
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Figure (9) Lithological identification cross-plots.
All the thin section were described by the point counter analysis and Petrographic
description shows in figure 12 and table 2 consist of Dolomitic quartz arenite, fine grained,
moderately to poorly sorted and moderately cemented, for detrital grains is Subrounded quartz and
are the main framework of the samples with minor amounts 1.5% lithic fragments and 0.5% grain
coating detrital clays, while the abundant authigenic cement is dolomite which occurs as well
crystalline rhombohedrons partially filling the pores and minor amounts 1% of syntaxial quartz
overgrowth. The pore network is consisting of very good interconnected oversized primary
intergranular and secondary dissolution intergranular porosity, so reservoir quality is very good.
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Figure (12): photomicrograph of Rudeis Fm in well 113-81.
Table (2) Point Country Petrographic Description of well 113-81
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Scanning Electron Microscope (SEM)
This is a type of electron microscope produces images of a sample by scanning it with a
focused beam of electrons. The electrons interact with atoms in the sample, producing various
signals that can be detected and contain information about the sample's surface topography and
composition. The electron beam is generally scanned, and the beam's position is combined with the
detected signal to produce an image. SEM can achieve resolution better than 1 nanometer.
Specimens can be observed in high vacuum, in low vacuum, in wet conditions (in environmental
SEM), and at a wide range of cryogenic or elevated temperatures (McMullan, 2006)
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Figure (13): SEM photo of well 113-81.
A: General view of the sample figure 13 shows in fine to coarse grained and moderately
sorted sandstone, with open grain packing and a high degree of well-connected primary
intergranular porosity . Pores are lined with some poorly developed authigenic clays and partially
filled by common dolomite rhombohedrons.
Figure (14): SEM photo of well 113-81.
B: Close-up photograph in figure 14,the same view, shows quartz overgrowths and pore-
lining bladed gypsum aggregates. These aggregates may be original or an artefact, (commonly
occur throughout the sample).
RESERVOIR CHARACTERASTIC
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The lateral variation of petrophysical characteristics are represented by a number of iso-
parametric maps which are the net pay isochore, shale content, effective porosity, water saturation,
and hydrocarbon saturation maps and this output data values are clarified in table 3.
Table 2: Petrophysical characteristic of Rudeis Formation.
Rudeis Formation- Net Pay vs Net Reservoir thickness Distribution Map
Figure (15) shows that the net pay in study area ranges between 20 m in 113-166-ST well to
112 m in 113-95 well. It is clear that the net pay increases towards the South Western part of the
study area. The structural elements of the area under study might affect the net pay distribution.
Rudeis Formation- Shale content variation map
Figure (16) shows that the shale content increases towards the North Eastern part of the area
under study, where the shale content recorded its maximum value of 18 % in 113-81 well.
Rudeis Formation- Effective porosity variation map
Figure (17) shows that the effective porosity increases towards the South Western part of the
study area with a maximum value of 22 % in 113-95 well.
Rudeis Formation- Water saturation variation map
WellsFormation
NameTop Bottom
Gross
Thickness
(m)
Net Pay
(m)
Effective
Porosity
PHIE (%)
Water
Saturation
(%)
Hydrocarbon
Saturation
(%)
Shale
Content
(%)
113-81 Rudeis Fm 2718 3048 330 105 21 30 70 18
113-95 Rudeis Fm 2750 2965 215 112 22 28 72 8
113-142 Rudeis Fm 2768 2892 124 61 19 33 67 5
113-166 ST Rudeis Fm 3071 3122 51 20 17 36 64 8
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Figure (18) shows that the water saturation increases towards the north eastern part of the study area, where the water saturation recorded its maximum value of 36 % in 113-166-St well.
Rudeis Formation- Hydrocarbon saturation variation map
Figure (19) shows that, the hydrocarbon saturation increases towards the West, central part
of the study area with a maximum value of 72 % in 113-95 well.
Figure (15): Net Reservoir Thickness Distribution Map
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30
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113-142
113-81
113-95
113-166(st)
61.00
105.00
112.00
20.00
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1:25000
0.0010.0020.0030.0040.0050.0060.0070.0080.0090.00100.00110.00120.00130.00140.00150.00160.00
Net pay [m]
C.I.=10 m
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Figure (16): Shale content variation map
0.25
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113-81
113-95
113-166(st)
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0.08
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657000
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658500
659000
659500
660000
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658000
658500
659000
659500
660000
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1:25000
0.000.050.100.150.200.250.300.350.400.450.50
VShale [%]
C.I.=0.05
0.21
5
0.215
0.21
0.21
0.20
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0.205
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113-142
113-81
113-95
113-166(st)
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1:25000
0.180.180.190.190.200.200.210.210.220.220.230.230.240.24
Porosity - effective [m3/m3]
C.I.=0.005
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Figure (17): Effective porosity variation map
Figure (18): Water saturation variation map
0.27
0.27
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113-142
113-81
113-95
113-166(st)
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829500 830000 830500 831000 831500 832000 832500 833000 833500 834000
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657000
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0.240.250.260.270.280.290.30.310.320.330.340.350.360.370.380.390.40.41
Water saturation
C.I.=0.1
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Figure (19): Hydrocarbon saturation variation map
Computer processed interpretation (C.P.I) plot
Figure (20) is the computer processed interpretation plot for Rudeis Formation in 113-
81well. As is shown in this figure20, the Rudeis Formation is encountered at the depth of (2718-
3048 m). The gross interval is 330 m. It is characterized by the predominance of sandstone and
shale. Shale tends to increase downwards and sandstone tends to decrease downwards where the
effective porosity ranges between(0.1% to 27%) but the mean value is 21%. The Rudeis Formation
reveals some intervals that the water saturation reaches to 16%. The water saturation ranges
between 16% to 60 %,but the mean value is 33 %. The Oil Water Contact is at 2824 (-2548) m and
the net pay is 105 m.
0.73
0.73
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0.7
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113-142
113-81
113-95
113-166(st)
0.67
0.7
0.72
0.64
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1:25000
0.590.60.610.620.630.640.650.660.670.680.690.70.710.720.730.740.750.76
Oil saturation
C.I.=0.01
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Figure (20) Petrophysics Logs Display of Rudeis Formation in 113-81 well
Porosity vs horizontal permeability relationship
Porosity-Permeability relationship is one factor from many to control the quality of
reservoir, so the relation is in figure 21 for Rudeis Formation of well 113-81 and the data in table 3
has one trend with excellent correction Coefficient (91 %). This reflect the good reservoir quality
which can delineate more fluids with high porosity.
Table 3: Out-put data of Horizontal Permeability (KH) versus Core Porosity from Routine Core
Analysis.
O.W.C @2824 (‐2548) m
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y = 1.0114e0.2945x
R² = 0.9122
1
10
100
1000
10000
100000
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0
Ho
rize
nta
l Per
mea
bili
ty (
md
)
Porosity (%)
113-81
Expon. (113-81 )
Figure (21) Porosity vs Permeability of Rudeis Formation for well 113-81.
Production Data
This is the production data of study wells which started producing in May 1997 from the
well 113-81 and are still producing till produced from the recent well 113-166 ST that started
putting in production in April 2011and formation water salinity measured from water samples that
have been taken during production and this is clarified in table 4.
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Table 4: Summary Production data of well study.
Wells Formation
Name
Daily Production
Rate m3/d
Cumulative
production
MMB
Water Resisitivity
Ohm.m
113-81 Rudeis 320 3 0.028
113-95 Rudeis 285 2.5 0.027
113-142 Rudeis 540 1.5 0.024
113-166 ST Rudeis 130 46 MB 0.025
I-Petroleum Potentialities
According to Magoon and Dow, (1994), the Petroleum system includes all those
geologic elements and processes that are essential for an oil and gas deposit to exist in nature.
These basic elements include a petroleum source rock, reservoir rock, seal, and trap; and the
geologic processes that create each of these basic elements. All these elements must be correctly
placed in time and space such that, the processes required formation a petroleum accumulation
can occur.
Source Rocks
According to Gluyas and Swarbrick (2004), a source rock is a sedimentary rock that
contains sufficient organic matter such that when it is buried and heated it will produced
petroleum (oil and gas).
The principal parameter in evaluating a rock unit to be a source rock is its organic
carbon content. Moreover, the type of organic matter determines to a great extent, the kind of
produced hydrocarbons being either oil or gas.
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According to Alsharhan, (2003), in prerift and synrift series the main source rock
corresponds to the marls of the Rudeis Formation. Its content in organic matter averages 2.5%
TOC but can locally reach 4% with a potential around 7kg/t. usually, the series of the younger
Kareem and Belayim formations may have a TOC in the range of1%.
Reservoir Rocks
According to Alsharhan, (2003), the Rudeis reservoirs are present over most of the study
area and represent about 20% of production potential in the Gulf of Suez. The Rudeis sandstone
has produced oil from fields such as the Shoab Ali, East Zeit, Ashrafi, Amal, Asal, Belayim
Marine, Belayim Land, Al Ayun, July, Kareem, Matarma, Sudr, Morgan, Kheir, and Umm El
Yusr and has tested gas from the Felefel field, the porosity ranges between 13 to 26%, and
permeability lies between 10 to 1000 md. The Rudeis carbonates are producers of oil in the Zeit
Bay, Bahr, Sudr, Asl, and Matarma fields and of gas in the Felefel field, with an average porosity
of 16%. These carbonates are particularly well developed in submerged high areas within the
lower Miocene basin.
Seal Rocks
According to Rashed, (1990), represent excellent seals for shallow-water limestone
reservoirs and were deposited as onlapping anhydritic evaporites during progressive eastward
basinal collapse and ongoing late-stage rifting events. Within the synrift sequence, however, the
Miocene evaporites are considered to be the ultimate seal for reservoir rocks in the Gulf of Suez.
This is particularly true in the southern and central Gulf of Suez, where the evaporites are
generally thick, either on the downthrown side of major Clysmic faults or in the downdip
direction of uplifted tilted fault blocks. However, the magnitude of throw on the Clysmic faults is
a critical factor in the effectiveness of the sealing mechanism (Meshref et al., 1988).
According to Saoudy, (1990), A small throw juxtaposes the evaporite section, on the
downthrown side, against the Miocene porous section on the uplifted block. A large throw brings
the Miocene evaporates in juxtaposition with the pre-Miocene reservoirs on the uplifted block, as
shown at the Hilal, Belayim Marine, and Belayim Land fields, while the Miocene clastic section,
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such as the Rudeis and Kareem formations, can act as seals especially in areas where some shaly
facies have developed. In such cases, porous intervals within the formation act as reservoirs,
whereas the shaly intervals become vertical and/or horizontal seals, depending on the magnitude
of the throw of the fault, the Miocene shales also are an important factor in stratigraphic traps,
where they confine a body of sandstone as a lateral facies variation.
Petroleum Entrapment
According to Magoon and Dow (1994), a trap is defined as any geometric arrangement
of rock that permits significant accumulation of hydrocarbon in the subsurface
According Salah and Alsharhan (1998), there are several mechanisms for petroleum
entrapment that are recorded in the Gulf of Suez. These are structural, stratigraphic, and
combination traps.
Structural Traps
In the Gulf of Suez, most oil accumulations are trapped structurally, the prerift and synrift
reservoirs produce oil from fault-related traps where the reservoir is laterally and vertically
confined by a down-faulted overlying seal.
Hydrocarbons in this type of trap are from either prerift sources across synthetic faults
(e.g., October, Belayim Land, Morgan, Geisum, and Shoab Ali fields) or the underlying prerift or
synrift sources, as in theHilal, East Zeit, Ramadan, and Ras Badran fields, and this type of
Petroleum Entrapment is represented in the study area.
Stratigraphic Traps
Stratigraphic traps have recently become important targets for hydrocarbon exploration in
the Gulf of Suez in general. There are some proven stratigraphic traps at the Ras El Bahar
discovery, where the Miocene porous carbonate wedge is sealed vertically and laterally by a
facies change to dense carbonate. In the Belayim Land Oil field, Miocene porous sandstone is
present as lenses that are sealed vertically and laterally by a facies change to evaporites. Oil
sources lie across faults or are located updip from the prerift sections.
International Journal of Scientific Engineering and Applied Science (IJSEAS) – Volume‐3, Issue‐6, June 2017 ISSN: 2395‐3470
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Combination Traps
According to A. S. Alsharhan, 2003, there are two proven cases of combination
traps. (1)In the Shoab Ali, Asl, Sudr, and Ras Matarma fields, the Eocene limestone is both
reservoir and source, with an updip contribution from the Upper Cretaceous carbonates and
sealed by synrift mudstones. In these fields some of the synthetic faults act as sealing faults. (2)
In the RR89 discovery and the Ras Gharib field, a reef reservoir deposited on a fault-controlled
high is sealed by Miocene evaporites.
CONCLUSION
As results of the present study concluded the following: Belayim Land is a large oil field
located in the central part of the Gulf of Suez, along the coast of the Sinai Peninsula, Rudeis
Formation is the main sandstone reservoir and considered as the most important hydrocarbon oil
bearing and represent about 20% of production potential in the Gulf of Suez with an average
thickness 180 m, average porosity 22 % and is a clean sandstone with average shale content 8 %.
The study area has all criteria to make it of considerable hydrocarbon potential. It is
characterized by having homogeneous lithological response relevant mainly to sandstone facies,
the hydrocarbon generating source rock, seal rock, reservoir rock, with reasonable porosity and
structure closure.
As results of the present study, using the subsurface and petrophysical evaluation, the
data of Rudeis Formation has one trend with excellent correction Coefficient (91 %). That
reflects the good reservoir quality which can delineate more fluids with high porosity.
As a result of the present study using subsurface and petrophysical evaluation, three
locations are proposed to be prospects in Rudeis formation as shown in figure (21). These
locations are structurally located within a three-way dip closure that is very attractive place for
hydrocarbon accumulation. Petrophysically these locations characterization by the following:
The first location, the red colored frame area, is located in the north of central part of the
study area (the reservoir is 215-330 m., the effective porosity is 22 %, shale content is 14 %, the
water saturation is 29 %, the hydrocarbon is 71 %). The second area is blue colored frame area is
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located in west of central part of the study area and characterized by the following;(the reservoir
is 51m ., the effective porosity is 17 %, , the shale content is 8 %, the water saturation is 36 %,
the hydrocarbon is 64 %). The third area is the green colored frame area is located in south of
central part of the study area and is characterized by the following ;(the reservoir is 124 m., the
effective porosity is 17 %, the shale content is 5 %, the water saturation is 33 %, the hydrocarbon
saturation is 67 %.
Figure (21): prospect map of Rudeis Formation.
Acknowledgements
International Journal of Scientific Engineering and Applied Science (IJSEAS) – Volume‐3, Issue‐6, June 2017 ISSN: 2395‐3470
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I wish to thanks the Belayim Petroleum Company (Petrobel), and General Egyption
Petroleum Corporation (E.G.P.C) for providing the used data in this study.
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