Factors Concerning the Development, Distribution and Preservation of
Reservoir
Facies
in Jurassic Carbonates and their Impact on Petroleum Systems in
Eastern and Northeastern Saudi Arabia
By
A/Motaleb Al-Qahtani1, Alastair Gray2, Geir K Ytreland2
(1) Saudi Aramco, Dahran, Saudi Arabia (2) Saudi Aramco, Dahran 31311, Saudi Arabia
The Rimthan Arch is a positive feature, which existed from Bajocian until
Portlandian time separating the Gotnia and Arabian intra-shelf basins throughout
this period. This feature, whose lateral extent has varied considerably
throughout time, significantly controls development of Jurassic reservoir
facies
.
The distribution and quality of the most important carbonate reservoirs in the
Eastern Province of Saudi Arabia appear to be controlled by a system of positive
elements; tectonic and/or depositional highs. Water depth, energy and primary
depositional environment created and/or modified the sediments into reservoir
rocks in the vicinity of these highs.
Analysis
of petrography, paleontology, core description work, core
porosity/permeability
analysis
and integration with well logs and
seismic
interpretation permit a reasonable description of the Upper Jurassic Arab
carbonate
facies
throughout the area, and are summarized into regional
facies
and net pore volume maps. Similarly, reservoir distribution maps for the other
reservoir units from this time are presented. An attempt is made to use sequence
stratigraphy and
seismic
stratigraphy to describe the systems, and to predict
facies
variation as it pertains to the development of petroleum systems and
prediction of various potential stratigraphic play types such as; dolomitization
as a sealing mechanism,
facies
variations, biohermal buildups and updip
reservoir pinchouts. Recent reprocessing of
seismic
data indicates that such
facies
variations may be seismically detectable.
Saudi Aramco oil typing work indicates a distinct separation of oil families into Gotnia and Northeastern Arabian Families and enhances the prospectivity of the Rimthan Arch trend.