In different areas of the Western Desert of Egypt, the Abu Roash “G” Member exhibits either a reservoir
or source affinity. Thus, thirteen cutting samples covering the Abu Roash “G” Member were selected from
the Nest-1A well at Matruh Basin to investigate its hydrocarbon source potential. Palynological age
dating of the section that is calibrated with foraminifera and ostracodes enabled a proper identification
of the “G” Member. Detailed analysis of the vertical distribution of particulate organic matter of this
member shows two palynofacies types. PF-1 reflects an outer middle shelf depositional environment of
prevailed reducing (suboxic-anoxic) conditions for the organic-rich shales of the lower “G” Member
(samples 1e8). While, PF-2 reflects a minor regression that resulted in deposition of another organic-rich
shales of the upper “G” Member (samples 9e13) in an inner middle shelf setting under the same prevailing
reducing (suboxic-anoxic) conditions.
Organic geochemical analysis reveals good to very good potential of the “G” Member as a hydrocarbon
source rock (1.8e2.41, avg. 2.15 total organic content wt %). It also shows good to very good petroleum
potential (PP: 4.8e11 , avg. 8 mg HC/g rock). Pyrolsis and palynofacies analyses show kerogen type II for
the lower “G” Member (samples 1e8), which is characterized by high Hydrogen index (HI: 396 and
329 mg HC/g TOC at depths 1500 and 1560 m) and very high dominance of oil-prone material (amorphous
organic matter “AOM”, marine palynomorphs, and sporomorphs) and very rare occurrence of gasprone
material (brown phytoclasts). The upper “G” Member (samples 9e13) shows kerogen type II-III,
which is characterized by a lower HI value of 213 mg HC/g TOC at depth 1340 m and it contains
fewer amounts of gas-prone material and relatively lower AOM and marine palynomorphs in comparison
to the upper “G” Member. Maturation parameters Tmax (430e433
C), production index (PI: 0.1 mg HC/g
rock), and thermal alteration index (TAI: 2þ) indicate the lower “G” Member has already entered the
early oil-window kitchen, and it is expected to produce oil. The upper “G” Member is expected to
produce only oil with no gas shows, because it is marginally mature (Tmax 426
C, PI 0.2, TAI 2). The
source potential index (SPI: 5.3 t HC/m2) of the “G” Member shows it as currently generating moderate
quantities of oil in the area of Nest-1A well.
Consequently, the organic-rich shales of the “G” Member are suggested here as a promising, active oil
source rock in that extreme northwestern part of the Western Desert of Egypt. However, for commercial
oil recovery from the Abu Roash “G” Member, it is highly recommended to explore the depocentre of
Matruh Basin at about 150 km east the Nest-1A well.