Print this pageReservoir Development in the Shuaiba Formation (Lower Cretaceous) at Al Barakah and Safah Fields, Oman - Similarities
D. R. Prezbindowski and W. C. Benmore
A detailed sedimentological and diagenetic study of the upper Shuaiba in the
Al Barakah and Safah Fields indicates that the critically important development
of secondary micro-intercrystalline 
porosity
postdates early meteoric water
diagenesis. The Shuaiba at Al Barakah and Safah Fields consists of shoaling
upward carbonate depositional cycles. The main reservoir is developed in the
upper cycle as discrete carbonate accumulations centered around rudist/algal
biogenic build-ups with surrounding, deeper water non-reservoir facies.
Reservoir porosity is dominated by secondary micro-intercrystalline (chalky)
porosity. A moderate sedimentological control on secondary porosity development
is evident. The best reservoir quality is developed in the coarse-grained,
skeletal-rich p ckstones associated with the carbonate build-ups. Although the
presence of a regional unconformity at the top of the Shuaiba has commonly been
thought to be responsible for reservoir porosity development, a lack of
petrographic and geochemical evidence for early meteoric water diagenesis has
made an evaluation of this reservoir development model difficult. Cores taken of
the Shuaiba and Nahr Umr contact in the Safah and Al Barakah Fields indicate
that meteoric diagenesis did occur, occluding early porosity. Reservoir porosity
development significantly postdates early meteoric water diagenesis, equant spar
calcite cementation and stylolitization. Porosity was formed by the dissolution
of the micritic components in the limestones during burial. Reservoir porosity
development in these field is not related to the regional input of meteoric
water at the Shuaiba unconformity surface.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California