Abstract The current work investigates the hydrocarbon
potentiality of the upper Jurassic–lower Cretaceous rocks
in the Marib-Shabwah Basin, Central Yemen, through the
Sabatayn-1 well. Therefore, palynological and organic geochemical
analyses were carried out on 37 ditch cutting and
12 core samples from the well. Palynofacies analysis of the
Madbi (late Oxfordian–early Tithonian) and Nayfa
(Berriasian–Valanginian) Formations sediments indicates
deposition of their organic-rich shale, calcareous shale and
marl in middle to outer shelf environments under dysoxic–
anoxic conditions, containing mainly kerogen of types II to
III. However, the shales of the lower Sabatayn (Tithonian)
Formation were deposited in an inner shelf environment of
prevailing dysoxic–suboxic conditions, and show kerogen
types III to II. Regional warmand relatively dry palaeoclimate
but with local humid conditions developed near the site of the
well is thought to have prevailed during deposition of the
studied well sediments. The geochemical analyses of the
Madbi Formation show higher total organic carbon content
(TOC) than the overlying Sabatayn and Nayfa formations: it is
varies between 1.2 and 7, and with average 4 wt% TOC, and
the obtained S2 values (∼3–10, average 7 mg HC/g rock)
indicates that the Madbi Formation is mainly good source
rock. It shows a good petroleum potential of 4–11 mg HC/g
dry rock, and the Rock-Eval pyrolysis indicates mainly kerogen
types II to III (oil to gas prone) of hydrogen index values
(132–258, and only one sample from Lam Member is of 360
and average 215 mg HC/g TOC). The thermal maturation
parameters as Tmax (425–440 °C), production index (average
0.13 mg HC/g rock) and thermal alteration index (2 to 2+)
reflected that this formation is present at margin of maturation
to early mature stage oil window. So, the Lam Member (upper
part) of the Madbi Formation is considered the main hydrocarbon
(oil and gas) source rock in the Marib-Shabwah Basin.
Accordingly, we predict that the Meem Member is an active
source for gas and oil accumulations in the overlying sandstone
reservoir of the Sabatayn Formation in the Sabatayn-1 well.