REAPPRAISAL OF KEROGEN TYPING ON LOW RANK COAL FROM SOUTH SUMATRA BASIN, INDONESIA

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

REAPPRAISAL OF KEROGEN TYPING ON LOW RANK COAL FROM SOUTH SUMATRA BASIN, INDONESIA

Hendra Amijaya

Department of Geological Engineering, Gadjah Mada University
Jalan Grafika 2, Yogyakarta 55281, Indonesia, Tel./Fax: +62-274-513668
Email: hamijaya@ugm.ac.id

ABSTRACT

The low rank coals from Tanjung Enim Area, South Sumatra Basin, Indonesia have a mean random huminite reflectance between 0.35-0.46% and are dominated by huminite (34.6-94.6%). Less abundant are liptinite (4.0-61.4%) and inertinite (0.2-44%) Minerals are found only in small amounts (max. 2.6%); mostly as iron sulfide. Rock Eval pyrolysis shows that the coals indicate lowest Hydrogen Index (HI) values of 171 mg HC/g TOC. Sample with high liptinite content even indicates HI values of 507 mg HC/g TOC. The Oxygen Index (OI) values are considered low (<25 mg CO2/g TOC). The mean value of Tmax is 420 °C. As depicted in HI – OI diagram, the samples are located at the conjugation line of the coalification paths of kerogen type I and II. Rock Eval analysis result shows that low rank coals from South Sumatra Basin do not generally respond as expected, where humic coal is considered as type III kerogen. However, from organic petrographic point of view, the kerogen type of the studied coals is mainly type III. In the sense of kerogen typing, coal should not be treated in the same way as dispersed organic matter.

Keywords: low rank coal, kerogen type, Rock Eval pyrolysis, organic petrography, South Sumatra Basin, Indonesia.