InterPreting effects of TOCinert organic content on source rock Potential using S2 vs. TOC graPh in Maamba Coalfield,southern Zambia

The authors present the effects of the total organic carbon (TOC inert ) during pyrolysis and how it overall affects the estimates of the hydrocarbon index (HI) using the cross plot S 2 vs． TOC graph． A total of 21 drillcore samples consisting of the non- carbonaceous mudstones，carbonaceous mudstones，coaly mudstones and coals with S 2 ＞ 0． 35 are selected and used． The average TOC for the sampled population is 10． 36 wt%． TOC inert measured from the S 2 vs． TOC graph is 2． 97 wt% and the average pyrolysable TOC live is 7． 39 wt%． The HI is 102 mg HC/g TOC and the pyrolysable HI is 175 mg HC/g TOC，indicating that the TOC inert or mi- neral matrix adsorbs some of the hydrocarbons liberated during pyrolysis resulting into the low HI values which affects the correct determination of the source rock potential． Other applications of the S 2 vs． TOC cross plot have been used to determine the depositional system tracts． The high stand system tract is also determined through this method．