The purpose of the study in the Karangkobar area was to investigate the source rock potential of the fine-grained surface samples of clastic sediments. The use of surface samples for source rock potential study in Indonesia is still limited. We conducted geochemical laboratory analyses in this research, including Total Organic Carbon (TOC), Rock-Eval Pyrolysis (REP), and Gas chromatography–mass spectrometry (GCMS). Seventeen samples have been analyzed for their TOC content. The result shows that TOC values varied between 0.36–1.55%, indicating that the source rock potential level based on the surface samples is poor to fair organic richness. REP was conducted on 16 samples, and the results show that the hydrocarbon-generating characteristics (HI values) ranged from 15 to 163 mg HC/g TOC. The kerogens identified included type II and III kerogen, which indicated the oil and gas-generating potential. Pyrolysis temperature is at maximum (Tmax) in the 276–458 °C, indicating that the samples were thermally immature to mature. GCMS analysis of source rock indicated that the depositional environment of the organic material derived from an open marine and plankton environment. This study is essential to complete the understanding of the petroleum system in Central Java.

Penelitian yang dilakukan pada singkapan batulempung di daerah Pemalang, Jawa tengah bertujuan untuk mengetahui karakteristik dan potensi batuan sumber hidrokarbon. Metode yang digunakan adalah penelitian di lapangan dan laboratorium. Penelitian di lapangan meliputi pengamatan litologi dan pengambilan conto batulempung. Analisa di laboratorium terdiri dari analisa TOC dan pirolisis Rock Eval. Hasil analisa TOC terhadap terhadap 11 conto batulempung menunjukkan nilai TOC sebesar 0,59-1,86 %. Tmaks 410-502oC menunjukkan tingkat kematangan belum matang hingga paska matang. Nilai HI berkisar antara 1-115 mgHC/TOC. Potensi hidrokarbon di daerah penelitian menunjukkan kategori material organik rendah dengan kerogen yang termasuk type III. Kualitas batuan sumber berdasarkan nilai HI termasuk dalam kategori gas prone.