Interpreting effects of TOC_(inert) organic content on source rock potential using S_2 vs. TOC graph in Maamba Coalfield,southern Zambia

摘要

The authors present the effects of the total organic carbon( TOCinert) during pyrolysis and how it overall affects the estimates of the hydrocarbon index( HI) using the cross plot S2 vs. TOC graph. A total of 21 drillcore samples consisting of the non-carbonaceous mudstones,carbonaceous mudstones,coaly mudstones and coals with S2> 0. 35 are selected and used. The average TOC for the sampled population is 10. 36 wt%.TOCinertmeasured from the S2 vs. TOC graph is 2. 97 wt% and the average pyrolysable TOCliveis 7. 39 wt%. The HI is 102 mg HC / g TOC and the pyrolysable HI is 175 mg HC / g TOC,indicating that the TOCinertor 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 S2 vs. TOC cross plot have been used to determine the depositional system tracts. The high stand system tract is also determined through this method.