Diagenetic evolution and carbonate reservoir quality of the Domerian-Bajocian South-Rifain Ridges, Morocco

Abstract

The Domerian-Bajocian sedimentary series of the South-Rifain Ridges display an alternation of various carbonate facies environments, dominated by a carbonate platform type environment. In order to study the diagenetic evolution and the quality of carbonate reservoirs, three areas are chosen, and twelve geological sections were investigated. The results obtained from this study allow to identify several diagenetic phases and to draw up an inventory of calcite versus dolomite, and ferriferous versus non-ferriferous cements. Other diagenetic phases identified are dedolomitization, silicification, sulfatization, recrystallization, dissolution, and mechanical compaction. The analysis of these phases shows that the diagenetic history of the sedimentary deposits composing the ridges can be summarized as a diagenetic sequence evolving from a deep marine to a continental tectonic uplift environment. This matches well the general model of evolution of a sedimentary basin. On the other hand, this sequence displays major variation from one area to another, and from one period to another, and it is dominated by early (Eo-diagenesis) and late (Telo-diagenesis) diagenesis. Meso-diagenesis is poorly developed in most of the geological sections studied. The diagenetic sequence is highly developed and complex, especially in the lower and upper Domerian of Jbel Kefs, the middle Domerian in the south of Jbel El Heitouf, and the middle Toarcian of Jbel Abd Elkrim. The results also show that the carbonate formations of the lower Aalenian in the northern flank of Jbel El Marcab, lower Bajocian in the eastern flank of Jbel El Heitouf, and middle Domerian in the eastern flank of Jbel Dehar En Nsour constitute a good carbonate reservoir.