Petrography and geochemistry of sandstone samples of Vischkuil formation, Karoo Supergroup, South Africa

A Akinlua,A Ngola,S A Adekola,O A Fadipe

doi:10.1007/s13202-015-0199-1

Abstract

Petrography and geochemistry of sandstones of Vischkuil formation in the Ecca Group of the Karoo Supergroup of South Africa was investigated to evaluate the petroleum potential of its reservoir rock. The petrographic analysis showed that the sandstones were poorly to moderately sorted with evidence of angular to sub-angular grains. The sandstones are lithic arenite. Diagenetic processes on the sandstone include physical and chemical compaction as seen from the straight grain contacts and dissolution of the quartz grains. There is an evidence of pore space reduction by the rearrangement and cementation by silica, calcite and clay minerals. The petrographic analysis also revealed that there is dominance of monocrystalline quartz grains and evidence of cratonic setting derivation. The chemical alteration index ranged from 52.96 to 65.5 %, an indication of a moderate weathering at the source area before deposition. The samples are texturally immature, which indicate poor storage capacity for fluids.

Highlights

Petrography and geochemistry have been part of the methods used in the evaluation of natural resource of which sandstone is one (Bheemalingeswara and Tadesse 2009)
The combination of petrographic and geochemical data of sedimentary rocks can reveal the nature of source regions, the tectonic setting of the sedimentary basins and the paleoclimate conditions (Jafarzadeh and Hosseini-Barzi 2008)
The main objective of this study is to evaluate the potential of Vischkuil formation sandstones as petroleum reservoir rocks based on the petrographic and geochemical analyses of the sandstones, and to describe the history leading to the sandstone formation

Summary

Introduction

Petrography and geochemistry have been part of the methods used in the evaluation of natural resource of which sandstone is one (Bheemalingeswara and Tadesse 2009). The use of these techniques has become very important in the search for hydrocarbon reservoirs. Geometry and orientations of grains and voids are the most important features of a rock pertinent to its origin. The relative depletion of oxides such as CaO, and Na2O and enrichment of SiO2 and TiO2 provides important clues for tectonic setting.

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Discussion

Conclusion