الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
Abstract
NEAG extension has been affected by two diverged consequent
forces. The NE-SW extensional forces comes first resulting in NW-SE
normal faults, followed by NE compressional forces of the Syrian arc system
causing the inverted structures and responsible for variations in both vertical
throw and thicknesses on the two sides of the former pure normal faults.
These forces ended by late Cretaceous in Khoman time. The Khoman is onlapping
on the condensed section of Abu Roach Formation in the west part
of study area.
Neag-1 located at the NEAG extension within the Abu Gharadig
basin margin at -1000 m_below sea level; Neag-1 represents the shallowest
structure in the study area and in all over the Abu Gharadig basin closer to
the highly inverted Kattania high but Neag-1 still preserves the trap integrity
for Hydrocarbon accumulation. The Neag-2 and Neag-3 are likely affected
with the same tectonic events with moderate magnitude closer to Natrun
basin in north direction.
The stratigraphy of the Bahariya in study area represents a sophisticated
setting affected primarily with the tectonic history of the area. Neag-2 and
Neag-3 most likely were far from the marine influence at lower Bahariya and
were not preserving the Upper Bahariya sediments. Meanwhile Neag-1 is
preserving the marine character and holding the thickest clastic of near-shore
sediments in the Upper Bahariya. The Bahariya-Kharita Para-conformity is
well defined at both Neag-2 and Neag-3 associated with fluviatile
distributary channels of second and third order.
The provided laboratory measurements to this study were used by
author to outline petrophysical properties of the Bahariya reservoir in order
to determine and evaluate porosity, permeability, pore throat radius,
formation factor, cementation factor, saturation exponent, cation exchange capacity and capillary pressure. The petrographic investigations are used for
outlining mineralogy, porosity types and mode of occurrence of formation
fines. The initial composition of the Bahariya rocks was dominated by
monocrystalline quartz, glaucony pellets, lithic fragments and feldspars
appeared as pore-filling and grain-coating shape.
The lithological variations and clay laminations have major influence
on petrophysical properties. Dissolution and cementation are considered as
the main pore framework controls in the Bahariya reservoir rocks. Illite,
kaolinite, calcite, dolomite and siderite are the common authigenic pore
filling minerals in the Bahariya samples. In general clay content of the upper
Bahariya is relatively higher than clay content of the lower Bahariya and it is
regularly associated with increasing of residual oil against the pores of
higher clay content.
The petrographical investigations showed the influence of the pore
filling minerals on petrophysical parameters as porosity and permeability.
Generally, the increase of pore filling minerals has a negative effect on both
porosity and permeability but without any unique signature for a single
mineral.
1. Petrophysical Studies
The reservoir properties has been investigated for the different
Bahariya facies (tidal channel, tidal bar, sand flat,…etc.) and rock types
(subfeldspathic Arenite, Feldspathic wakes, ….) that shows poor correlation
and less significance petrophysical characteristics as most of the high quality
rocks was affected by cement alteration and secondary porosity.
The Bahariya facies are influenced by different and mixed
sedimentary agents among the shallow marine and fluvial, although they
were present at the same time. The identified rock types showed up to 50 %
subfeldspathic arenites, with clear effect of diagenesis that reform and reshape the cement content inside the rock. This phenomenon is accounting
for these changes in the Bahariya as a result of tectonics setting and uplifting.
The mineralogy aggregates in-between the pores are from mixed
lithology in variable amounts between kaolinite, illite, calcite, dolomite and
siderite. Quantielan model is created from open hole logs to highlight this
mixed mineralogy of Bahariya lithology. The results account for the
reservoir lithology and pore filling minerals.
The petrophysical correlations between porosity and pore filling
minerals showed linear relation as at 50 % pore filling there is no porosity
expected in the rocks. Permeability versus total pore filling minerals showed
four classes in power relation. These classes are investigated with pore throat
size measured by (MICP) to assess types of flow. Types of fluid flow are
micro-pores, micro-meso pores, meso pores and macro pores, these types
representing and shaping the hydraulic conductivity of the Bahariya reservoir
rocks. The intercorrelation among porosity, permeability and pore throat
radius (r35) is formulating the hydraulic flow units of the Bahariya reservoir.
1.1. Porosity
Porosity of the Bahariya samples were investigated in both cores and
borehole logs calibrated with core porosity. Porosity is statistically varies
from 2.5 to 32 % with mean value of 19 %. The pore spaces is filled with
clay minerals and calcareous cement decreasing the porosity while the higher
porosity samples are mainly of secondary origin which affected by partial to
near complete dissolution of carbonate cements and k-feldspars.
1.2. Permeability
Permeability of the Bahariya samples varies from 0.005 mD to 874 mD
with mean value of 54.75 mD. The permeability samples characterized by
gradual increase of pore aperture to 2 μm (micro –meso pores); macro porosity type > 2 μm which showed the higher permeability. Samples No.
3R and No. 4R are showing total cement dissolution in thin sections and
significant capillary curves are observed.
1.3. Pore throat radius;
The calculated pore throat radius of the studied Bahariya samples are
varies from 0.3 μm to 3.55 μm with mean value of 2.1μm. The mathematical
approach to calculate pore throat radius from porosity and permeability
equations is ranging from 0.13 μm to 3.89 μm with mean value of 1.12 μm.
The higher pore throat radius is represented in many samples as they affected
by partial to near complete dissolution of carbonate cement and k-feldspars.
2. Hydraulic Conductivity
The hydraulic conductivity of the Bahariya samples showed high
degree of heterogeneity in pore spaces especially in Neag-1 field. The
hydraulic flow units approach was used to study this heterogeneity. Ten
hydraulic flow units are obtained, while each one has unique pore throat
radius (r35) controlling the pore geometry. The first HFU holds the lowest
reservoir quality while HFU-10 is the best reservoir quality. The Bahariya
reservoirs can be divided into three main types’ according to pore systems
characteristics of their hydraulic conductivity, to micro-pores, meso pores
and macro pores. The overlapped area between micro-meso pores is not
sharply identified due to limitation in the number of MICP test but this
overlap is happened as a result of the partial dissolution of k-feldspars and
calcareous cement in pores. This boundary is well identified by graphical
methods (storage and flow capacities).
Coefficients of micro-meso pores and macro pores showed different
correlations with porosity, permeability, residual oil saturation and pore
throat radius (r35). It is used to build a saturation height function with Lambda method. The water saturation in the transition zone is addressed
with characteristic equations function of capillary pressure comparing
between the J-function and lambda methods. The lambda fitting gives more
representative equations of capillary curves than the J-function. Seven
reservoir curves were initiated for porosity starting from 5 to 35 % using the
lambda method. The coefficients (a) and (λ) is ranging from 1.1 to 1.3 and
0.22 to 0.33 respectively.
3. The Electrical Conductivity
The Bahariya reservoirs in the presented study can be divided into
four main types’ of electro-facies as: 1) clean sand, 2) shaley sand (sand
flat), 3) siltstone and 4) shale as structural and dispersed sand doesn’t exceed
3 %. The borehole logs showed low vertical resolution (10 cm) according to
that any thin beds will be missed. The high resolution borehole images (0.5
cm) are helpful in borehole logs calibration. Three different equations can
conclude and characterize the Bahariya reservoir electro-facies.
The saturation exponent (n) increases with the increase of
cementation factor (m); these coefficients showed poor correlation compared
with hydraulic conductivity coefficients. Cation exchange capacity and
mounce potential is showing poor correlation with most of the investigated
petrophysical parameters. Kaolinite and saturation exponent of Archie are
found to be functions of cation exchange capacity (CEC) and mounce
potential (ϕ).
Formation factor (F) showed relatively good correlation with the
cation exchange capacity (CEC) and mounce potential (ϕ) in both clean and
shaley sands. While in siltstone the CEC is above 0.63 sm-1 showed poor
correlation with formation factor (F). 3.1. Formation Factor
Formation factor of the Bahariya samples varies from 14.4 to 44.7
with mean value of 26.7. The Formation factor is characteristic for clean and
shaley sand; shaley sand has higher formation factor value than the clean
sand samples as the formation factor increase with the decrease of porosity
and tortuosity. The Archie multiplier (a) is estimated in clean sand as 0.6 and
for shaley sand is 0.55, the cementation factor in clean sand is ranging from
1.95 to 2.2 with mean value of 2.07 and shaley sand is ranging from 1.79 to
2.02 with mean value of 1.87.
3.2. Formation resistivity index
Formation resistivity index is mainly used to calculate the saturation
exponent (n) of the Bahariya samples dominated by salinity and brine
saturation. Saturation exponent varies from 2.0 to 2.67 with mean value of
2.36. The higher cementation factor (m) the higher saturation exponent (n);
while the coefficient of correlation is founded to be 0.90 between them.
3.3. Cation exchange capacity
Cation exchange capacity (CEC) of the Bahariya samples varies from
-1.09 to -0.07 sm-1 with mean value of -0.46 sm-1. The higher quantity of the
clay minerals the higher cation exchange capacity (CEC) and mounce
potential (ϕ); the coefficient of correlation between them is 0.83. Cation
exchange capacity has higher values in shaley sand and fine siltstone.
4. Borehole logs
Open hole logs are used to validate and calibrate the shaley facies of
the Bahariya with high resolution borehole image and further Qaunti-elan
model is produced from well logs responses calibrated with the petrography
of the Bahariya reservoir. The lower Bahariya is rich in glauconite, kaolinite
and illite; carbonate cement is common in the Bahariya reservoir which increases the matrix density to 2.69 gm/cc as porosity is calculated from
logs. The porosity were investigated and calibrated by core porosity with
calculated equations. The log Porosity of the Bahariya is statistically varies
from 0.6 to 36 % with mean value of 14 %, the variance is 29, skewness is
0.19 and kurtosis is -0.16. The kurtosis remains positive for all zones but for
the lower Bahariya zone it gives negative sign.
The borehole logs are used to validate the rock properties; such as the
bulk density and photo electric factors is influencing porosity and
permeability. The photo electric factor is indicating the cement, lithology
while, bulk density is high in low porosity and permeability rock samples.
4.1. Fluid Saturation
Water and hydrocarbon saturation are calculated by different
methods; from open hole logs , core measurements and integrated open hole
logs and core using Archie, Indonesia, Simandoux, Waxman smith and low
resistivity pay. Among all these methods Waxman Smith and LRP are found
to meet the realistic saturation measured by laboratory method. The cation
exchange capacity value for each electro-facies is solving the clay extra
conductivity masking hydrocarbon zones in the borehole logs.
5. Petrophysical Models
Several formulas have been developed and eight petrophysical
models having high and reliable coefficient of correlation. The reservoir
heterogeneity is solved by the hydraulic flow units while permeability can be
predicted and obtained correctly from two parameters while the extra low
permeability layers less than 0.4 mD is not consistent in hydraulic
conductivity. The mercury injection capillary pressure proved high tortuosity
in hydraulic flow units (HFU-1&-2) with limited storage capacity 2.5 % but starting from hydraulic flow unit (HFU-3) the storage and flow capacity are
increased.
The results showed good correlation between Waxman smith and low
resistivity pay methods and the same for hydraulic pore volume derived from
initiated capillary curve which indicated by matching with coefficient of
correlation reaching 0.9 and low covariance 0.04.