Traps Resulting from Differential Compaction of Sediments

Traps Resulting from Differential Compaction of Sediments 

A particular type of non-structural traps has been observed, resulting from differential compaction in the sandy-argillaceous Triassic sediments. 

These are not regional trends but variations on a structural scale. In the sediments of the arenaceous-argillaceous Triassic it is frequently observed that structural features are accentuated by differential compaction. The large sandy channels like those encountered on the Sef Fatima structure (SF-i) may be resistant to compaction whereas the peripheral shales are strongly compacted (Fig. 2.17). Such structures may lead to the trapping of oil mid-flank on the structures in the crevasse-splay sandstones with sloping aquifers whereas the top of the structure is completely empty. 

The drill holes targeted on the Triassic in the Eastern Erg only explored the summit areas of these structures and this type of prospect was not recognized. It has to be pointed out, however, that these crevasse-splay sandstones are considerably thinner than the channel sandstones. 

This situation is well developed on the Berkane structure (BRK-i) where the Triassic structure is derived from a Paleozoic structure present on the Hercynian unconformity as a high (Fig. 2.17). This wedging-out exhibits two aspects  

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