Paleofacies of Eocene Lower Ngimbang Source Rocks in Cepu Area, East Java Basin based on Biomarkers and Carbon-13 Isotopes

Global Colloquium on GeoSciences and Engineering 2017

Devi, Elok A.^1 ; Rachman, Faisal^2 ; Satyana, Awang H.^3 ; Fahrudin^1 ; Setyawan, Reddy^1

Geological Engineering Department, Diponegoro University, Indonesia^1

Joint Operating Body Pertamina-PetroChina East Java (JOB P-PEJ), Indonesia^2

Special Task Force for Oil and Gas (SKKMIGAS), Indonesia^3

关键词: Aromatic fraction;    Carbon-13 isotopes;    Exploration wells;    Geochemical data;    Hydrocarbon source rocks;    Paleogeography;    Sedimentary facies;    Source evaluations;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/118/1/012009/pdf
DOI  :  10.1088/1755-1315/118/1/012009

来源: IOP

【 摘 要 】

The Eocene Lower Ngimbang carbonaceous shales are geochemically proven hydrocarbon source rocks in the East Java Basin. Sedimentary facies of source rock is important for the source evaluation that can be examined by using biomarkers and carbon-13 isotopes data. Furthermore, paleogeography of the source sedimentation can be reconstructed. The case study was conducted on rock samples of Lower Ngimbang from two exploration wells drilled in Cepu area, East Java Basin, Kujung-1 and Ngimbang-1 wells. The biomarker data include GC and GC-MS data of normal alkanes, isoprenoids, triterpanes, and steranes. Carbon-13 isotope data include saturate and aromatic fractions. Various crossplots of biomarker and carbon-13 isotope data of the Lower Ngimbang source samples from the two wells show that the source facies of Lower Ngimbang shales changed from transitional/deltaic setting at Kujung-1 well location to marginal marine setting at Ngimbang-1 well location. This reveals that the Eocene paleogeography of the Cepu area was composed of land area in the north and marine setting to the south. Biomarkers and carbon-13 isotopes are powerful data for reconstructing paleogeography and paleofacies. In the absence of fossils in some sedimentary facies, these geochemical data are good alternatives.