Online Journal for E&P Geoscientists

Aqrawi, Adnan A.^*1; Skarpnes, Oddvar ¹; Scotchmer, John ¹; Almasri, Ahmed ²
(1) Statoil ASA, Stavanger, Norway. (2) Natural Resources Authority, Amman, Jordan.

The Lower Palaeozoic of northwest Arabia is characterised by similar major chrono-stratigraphic rock units, covering vast areas of eastern Jordan, northwest Saudi Arabia, eastern Syria and western Iraqi deserts. It is the most under-explored succession in Iraq, but it is considered to have significant exploration potential.

The Lower Silurian marine (hot) shale is the main proven source rock for the Palaeozoic hydrocarbons discovered in the area of study. However, some Upper Ordovician black shales (of the Khabour Formation of Iraq and its equivalent in Jordan) are also expected to be additional local source rocks within the region. Conversely, the Lower Ordovician Hiswah graptolitic shales of Jordan are originally lean, where analysed, and are not considered to be a major hydrocarbon source rocks. Similarly, preliminary geochemical results show that the Middle Cambrian Burj limestone does not have significant source potential in the marginal Jordanian wells, although it may have some potential where deposited in a more basinal settings such as in western Iraq.

Several promising sandstone reservoir rocks (of Cambrian, Ordovician, and Early Silurian ages) are present across the study area. However, the reservoir quality is a major exploration risk as most of these sandstones have been severely affected by quartz overgrowth and clay cementation. Only some Upper Ordovician Dubaydib subsurface sandstones of Jordan have chlorite-clay coatings, which prevented formation of the quartz overgrowth, preserving good reservoir quality. Seals are also available all-over the region both on local and regional scales; these include (but are not limited to) the shales and carbonates mentioned above as potential source facies.

The widespread occurrence of potential source, reservoir and seal rocks suggests that Lower Palaeozoic prospects below the deserts of western Iraq are quite promising frontiers for future hydrocarbon exploration.