Facies deltaic

Triassic sediments are deposited only in the eastern and northern parts of the Sahara, in the Triassic Province. Triassic sandstones are mainly a combination of deltaic to prodeltaic facies represented by upper deltaic fluvial system deposits, lower distributary channel rivers, mouth bars, beach sands and tidal flat and prodeltaic shales. Typical marine Triassic shales are restricted in extent in the study area. Triassic Lower, Middle and Upper sandstones are stratigraphically separated by shale intervals, but occasionally also by carbonates or volcanic interbeds. They are often medium grained, and range from friable to cemented with clay mineral, carbonate, anhydrite and siliceous cement. Porosity ranges from 12 to 22%. With respect to mineralogical composition and maturity, Triassic sandstones are mature sublitharenite (Lower Triassic), sublitharenite to submature subarkose (Middle Triassic) and submature subarkose (Upper Triassic). 

Object-based facies modeling is applicable to many different depositional settings. The main limitation is coming up with a suitable parameterization for the geologic objects. Deltaic or deep-water lobes are one object that could be defined. Eolean sand dunes, renmant shales, and different carbonate facies could also be used. 

In every exploration program it is a must to find out in what kind of deposi-tional environment the investigated rocks were generated. To locate reservoirs it has to be known if they were generated in a deltaic, fluvial or reef environment. Reservoir sands in a reef environment show a different seismic facies than sands of a fluvial environment. If the depositional environment of a sedimentary rock is known then further exploration and production strategies can be refined and optimised. A tool to describe depositional environments out... 

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