GEOCHEMICAL ASSESSMENT OF THE PETROLEUM SOURCE ROCK POTENTIAL IN LOWER SHIRE BASIN (MALAWI)

One of the essential steps in hydrocarbon exploration and exploitation is to understand the source rock evolution and the related petroleum system. Understanding how and where hydrocarbons were originated, help to comprehend, and predict where they can be discovered. Geochemical source rock evaluation provides valuable information ready to be used for upgrading areas under investigation, concentrating exploration activities in particular places and reducing risks.

This study involved use of geochemical parameter (TOC, HI, OI, PP, GP, S2, S1 etc.) which was delivered from rock eval pyrolysis process to classify organic matter richness, kerogen types and their thermal maturity of hydrocarbons present in the collected rock samples. Geochemical analysis of the surface cretaceous sedimentary rocks was undertaken to understand oil and gas potentially of the petroleum source rocks in the lower shire river, based on the case study on the two basins namely, Lengwe and Mwabvi.

Shire basin is located within middle east Africa, and it is made up of perma-Triassic and cretaceous sedimentary rocks and intruded by a variety of alkaline rocks of Jurassic to cretaceous age. It is located within eastern Africa rifting valley that was developed and is associated with the rifting process.

Geochemical methodology approach has been used in assessment of petroleum source rocks whereby data collected from eval rock pyrolysis process has been used. Excellent organic matter richness has been measured in each rock sample as indicated by high TOC values which is of greater than 2wt%. Very poor and fair petroleum potential has measured for the samples indicated by very low S1 and S2. Many samples have shown to be in post-maturity window, two samples are in mature and one in immature window hence giving hope and encourage for some more exploration to be conducted in the area. Thus, a considerably amount of petroleum that has already been generated from them, type IV kerogen have been reported for all samples, indicating inactive source rocks.