Central Arabia basin
History of the Basin (highlight major fields)
Primary Geologic Risks
The Central Arabia Qusaiba-Paleozoic TPS (Total Petroleum System) is one of two petroleum systems in the Central Arabia basin. The main formation in this system is the Qalibah formation, which includes the important member, Qusaiba. The organic-rich shale facies of the lower Qusaiba member of the Qalibah formation is the source rock for this particular system in the Central Arabia basin.
The Qalibah formation consists of the lower Qusaiba shale, upper sandstones, siltstones, and shale of the Sharawra formation. The lower Qusaiba member contains coarsening upwards sequence due to the deglaciation in the early Silurian, while the upper member has a fining upwards sequence. The basal hot shale of the lower Qusaiba member is the source rock of this system as shown by the well logs on Fig.1.
The lower Qusaiba hot shale is a dark-grey, micro-laminated, euxinic shale with a TOC that can reach up to 20 wt%. While sandstone facies in the formation have a thickness range of 1-30cm, the hot shale bed thickness is around 75cm. A survey done by Jones and Stump (1999) showed that the richest and thickest source rock occurs on the flanks of the depocenter, rather than within it as described by other researches.
The other petroleum system in the central Arabia basin is the Arabian sub-basin Tuwaiq/Hanifa-Arab TPS. Two organic-rich intervals or marine sandstones and marls make up the source rock of one of the world’s largest single-oil fields.
HC type/ Maturation
Primary and Secondary Reservoirs
Analysis of any Geologic uncertainties
Current future assessment of the basin including EOR.
EOR using CO2 is currently being implemented in Saudi Arabia to help increase the amount of oil recovered. The project uses around 40 MMscf of CO2 to be injected from a gas plant about 85km away from the field. The project was first introduced in 2006, while setting a plan that the project would start in the late 2010’s. The execution relies on four injectors and four producers that are placed up-dip around 600m away from the injectors, with the wells being between them (Fig.2). The CO2 from the gas plant is planned to be captured, compressed, dehydrated, and transported to the injector wells through pipelines as shown in the schematic below (Fig.3). the four injectors and producers are designed specifically for this project. The injection has started in 2016, but no data about it is available now.
Reference (min 5)
Jones, P.J., and Stump, T.E., 1999, Depositional and tectonic setting of the Lower Silurian hydrocarbon source rock facies, Central Saudi Arabia: American Association of Petroleum Geologists Bulletin, v. 83, p. 314–332.
Kokal, S., Sanni, M., and Alhashboul, A. 2016. Design and Implementation of the First CO2-EOR Demonstration Project in Saudi Arabia. Presented at the SPE Annual Technical Conference and Exhibition, Dubai, United Arab Emirates, 26—28 September. SPE-181729. http://dx.doi.org/10.2118/181729.
Pollastro, R. (n.d). Total Petroleum Systems of the Paleozoic and Jurassic, Greater Ghawar Uplift and Adjoining Provinces of Central Saudi Arabia and Northern Arabian-Persian Gulf. Retrieved from https://pubs.usgs.gov/bul/b2202-h/b2202-h-508.pdf