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7th Middle East Geosciences Conference and Exhibition
Manama, Bahrain
March 27-29, 2006
Sandstone
), Southwest Saudi Arabia
1 Earth Sciences Department, KFUPM, Dhahran,
31261, Saudi Arabia, phone: +966500924386, fax: +966 3 860 2595,
[email protected]
2 KFUPM
The Cambro-Ordovician Dibsiyah member of Wajid Sandstone at Wadi Ad-Dawasir has its subsurface equivalent to the
east in the Rub Al-Khali basin, which is a frontier hydrocarbon province in SE Saudi Arabia. This study aims to characterize
the Dibsiyah member by integrating facies and architectural analysis, petrographic and petrophysical (porosity,
permeability) as well as geostatistical analysis.
The Lower Dibsiyah member consists of medium to very coarse, moderately to poorly sorted sandstone facies. Facies
recognized include channel massive to trough cross-bedded micro conglomerate, trough cross-bedded, planner crossbedded
and massive sandstone facies and minor massive to laminated mudstones which occur as thin interbeds or drapes.
The facies suggest deposition within channel and bar complexes of a bedload dominated low -sinuosity stream.
The Upper Dibsiyah consists of fine to medium, pebbly moderately to well- sorted massive to cross-bedded conglomerate,
trough cross-bedded, planner cross-bedded and horizontally bedded and herring-bone cross-bedded sandstone facies.
Massive mudstone and laminated shale are subordinate. Skolithos rich horizons dominate the sandy facies in the upper
part. The facies suggest deposition within shallow marine environment.
Both the Lower and Upper Dibsiyah show variations in their texture, composition, sandstone body thicknesses, geometry,
stacking patterns and vertical and lateral connectivity. These variations in macro to micro scale characteristics indicate both
depositional and post-depositional controls. The results of the outcrop study is expected to be critical and of considerable
use in understanding and prediction
of reservoir properties of the Dibsiyah subsurface equivalent in the Rub Al -Khali basin.