Abstract
Petrographic studies show that the Sarir sandstone in composition from (sub-arkose to arkosic aren- ite). During early diagenesis, the Sarir sandstones were modi ed by calcite, dolomite, and locally pyrite, diagenesis process; replacements of corroded silica by carbonates. Cementation uvial sand- stones Intrastratal dissolution and precipitation of kaolinite in the resulting pore space. Deformation of micas between more resistant grainy pre-dates one phase of quartz overgrowth, probably the car- bonates. The methodology was conducted with the review of the previous; published papers, the open le of the Arabian Gulf Oil Company (AGOCO). Thin sections were used for the petrographic analysis with polarized and scanning electron microscopes (SEM). The results of the study were: subsurface investigations including cores (conventional and side walls), petrographic analysis, and wire-line logs suggested that this formation (Sarir sandstone) can be divided in to three main units in Messla oil eld. The quarzitic sandstones of (the lower and the upper Sarir sandstones) are considered to be the main producing horizons where quartz grains have undergone a complex diagenetic history, including: authigenesis, quartz and feldspar overgrowths, dissolution, carbonates cementation, and replacement. The nature of the shale facies, (i.e. lack of organic content, and presence of oxidizing conditions indicated by iron oxides color, indicate that they are not a signi cant source of hydrocarbons. On the other hand, the Rakb shale is the only source rock in the studied and adjacent areas.