Ghaba salt basin province and Fahud salt basin province, Oman; geological overview and total petroleum systems

Three Total Petroleum Systems each
consisting of one assessment unit have been
identified in the Ghaba and Fahud Salt Basin
Provinces of north-central Oman. One Total
Petroleum System and corresponding assessment
unit, the North Oman Huqf/?Q??Haushi(!)
Total Petroleum System (201401) and Ghaba-
Makarem Combined Structural Assessment Unit
(20140101), were identified for the Ghaba Salt
Basin Province (2014). In the Fahud Salt Basin
Province, however, two overlapping Total
Petroleum Systems (TPS) were recognized: (1)
the North Oman Huqf?Shu?aiba(!) TPS
(201601); Fahud-Huqf Combined Structural
Assessment Unit (20160101), and (2) the middle
Cretaceous Natih(!) TPS (201602); Natih-Fiqa
Structural/Stratigraphic Assessment Unit
(20160201). The boundary for each Total
Petroleum System also defines the boundary of
the corresponding assessment unit and includes
all trap styles and hydrocarbon-producing
reservoirs within the petroleum system.
In both the Ghaba and Fahud Salt Basin
Provinces, hydrocarbons were generated from
several deeply buried source rocks within the
Infracambrian Huqf Supergroup. One general
?North Oman Huqf? type oil is dominant in the
Fahud Salt Basin. Oils in the Ghaba Salt
Basin are linked to at least two distinct Huqf
source-rock units based on oil geochemistry: a
general North Oman Huqf-type oil source and a
more dominant ?questionable unidentified
source? or ?Q?-type Huqf oil source. These two
Huqf-sourced oils are commonly found as
admixtures in reservoirs throughout northcentral
Oman.
Hydrocarbons generated from Huqf sources
are produced from a variety of reservoir types
and ages ranging from Precambrian to
Cretaceous in both the Ghaba and Fahud Salt
Basin Provinces. Clastic reservoirs of the
Gharif and Al Khlata Formations, Haushi
Group (middle Carboniferous to Lower
Permian), dominate oil production in the
Ghaba Salt Basin Province and form the basis
for the Huqf/?Q??Haushi(!) TPS. In contrast,
the Lower Cretaceous Shu?aiba and middle
Cretaceous Natih limestones account for most of
the production in the Fahud Salt Basin with
about 50 percent of the basin?s production from
porous, fractured Shu?aiba limestones in Yibal
field, thus the name North Oman Huqf?
Shu?aiba(!) TPS. Deep gas is produced mainly
from Middle Cambrian to Lower Ordovician
clastic reservoirs of the Haima Supergroup.
Traps in nearly all hydrocarbon accumulations
of these petroleum systems are mainly
structural and were formed by one or more
3
mechanisms. These trap-forming mechanisms
were mainly periodic halokinesis of the thick
Cambrian Ara Salt and consequent folding and
faulting from basin loading, rifting, or other
major tectonic events, particularly those events
forming the Oman Mountains and associated
foreland-basin system during the Late
Cretaceous and late Tertiary.
Many of the future new-field targets will
likely be low-relief, subtle structures, as many
of the large structures have been drilled.
Oman?s recent interest and commitments to
liquid natural gas export make deep gas a
primary objective in the two North Oman Huqf
petroleum systems. New-field exploration of
deep gas and exploring deeper targets for gas in
existing fields will likely identify a
significant gas resource in the next 30 years.
Moreover, salt-diapir flank traps in these two
North Oman Huqf petroleum systems and salt
basin provinces have gone essentially untested
and will likely be targeted in the near future.
The middle Cretaceous Natih(!) TPS is a
small efficient system of the Fahud Salt Basin.
Natih source rocks are only mature in the Late
Cretaceous/Tertiary foredeep and production is
primarily from Natih reservoirs; minor
production from the Shu?aiba limestone is
documented along fault-dip structures. Most
traps are structural and are related to
development of the foreland basin and
formation of the Oman Mountains. Future
targets of the Natih TPS will be less obvious