Shu’aiba Fm
Type Locality and Naming
Is in B.P.C. Well Zubair No. 3, South Iraq. The type section, described by H.V. Dunnington (1959), is quite unlike this, being composed of fine-grained, chalky and argillaceous limestones, some of which contain globigerinids, interbedded with shales in their upper and lower parts. R.M.S. Owen and S.M. Nasr, 1958 (amend. H.V. Dunnington, 1959). R.M.S. Owen and S.M. Nasr (1958) describe the Shu’aiba Formation as “made up of dolomitic limestones which are coarsely crystalline, porous and cavernous, with recrystallised Rudistae and with rare Orbitolina discoidea and Choffetella decipiens”.
Synonym: “Shuaiba Formation”, Dominguez, 1965. “Shuaiba Formation”, Powers, 1968. “Shuaiba Formation”, Harris et al., 1968.
Reference Section:
Q.P.C. Well Dukhan No. 11, lat. 25°27’17” N, long. 50°48’02” E, elevation 41.5 m (136 ft), completed 1.8.1949, between drilled depths 1006 and 1135 m (3291 and 3724 ft).
Lithology and Thickness
Top. 1. Limestone, light grey or white, chalky and white chalk. 26 m (85 ft). 2. Limestone, white to light grey, chalky, containing fine, calcareous, organic debris. Partly strongly recrystallised. Occasionally dolomitic. Grey and argillaceous in bottom few feet. 106 m (348 ft). Base. Thickness is 132 m (432 ft)
Relationships and Distribution
Lower contact
Hawar Fm; contact conformable. Placed where limestones of the basal Shu’aiba overlie blue-grey shales of the Hawar.
Upper contact
Nahr Umr Fm; contact probably disconformable; at contact of grey limestone of the Shu’aiba, below, with the shales of Nahr Umr Fm.
Regional extent
GeoJSON
Fossils
In 1. Arenobulimina sp., Pseudochrysalidina sp., and Orbitolina cf. discoidea Gras. In 2. O. cf. discoidea, Cardita cf. upwarensis.
Age
Depositional setting
Additional Information
The Shu’aiba Fm has recently become an important oil-producing reservoir in the neighbouring state of Abu Dhabi and has, in consequence, been the subject of detailed study. The Shu’aiba Fm of the Bu Hasa Field is comparable to the coarse rudistid limestones recorded from Kuwait. The type section in S. Iraq, appears to show more affinity to the equivalent deeper-water sequence which occurs at the top of the Thamama Gr in the Bab Dome (T.J. Harris, J.T.C. Hay and B.N. Twombley, 1968).
The Shu’aiba Fm of Qatar has been almost exclusively examined as well cuttings and its detailed lithology cannot, consequently, be determined. It has been described, in general, as a chalky, Orbitolina-bearing limestone but much lithofacies variation undoubtedly occurs over the peninsula. It is, probably, more closely related to the shallow platform facies of Bu Hasa and Kuwait since deeper-water limestones like those seen in the type section and in parts of Abu Dhabi have not been recognised.
The name Sabsab Fm was at one time assigned to a distinctive lithologic unit, composed of grainstones or packstones with abundant abraded Orbitolinae, described from many Dukhan wells. This is now included in the Shu’aiba Formation.