3D MODELING OF KEREK TURBBDITE SAND BODIES BASED ON OUTCROP STUDY IN KEDUNGJATI AREA, CENTRAL JAVA: AN ANALOG FOR SANDY MIOCENE FORMATIONIN WESTERN KENDENG ZONE

摘要

During the Eocene to the Miocene, Kendeng zone was the main depocenter in the North East Java basin. It is a back arc basin related to Oligo-Miocene volcanic arc, resulting from the uplifting of Southern Mountain Zone of Java and filled with thick pelagic and volcaniclastic sediments. This paper emphasizes determination of the facies, distribution and geometry of Miocene Kerek sand bodies. The main data is based on outcrop data considered as having high reliability to support subsurface studies, related to turbidite sands reservoir geometry and distribution.This study uses 8 measuring sections generated along river traverses in study areas and 10 outcrop rock samples. The samples have then been analyzed to describe and are characterized using petrography, paleontology and sedimentology analyses. Based on iacies analyses, there are three depositional facies of Kerek sand, consisting of a shallow channel of submarine lower fan, a lobe of submarine lower fan, and pelagic mud deposits. Statistical analysis is also being used to characterized Kerek sand, and describe it more in geometry into: (1) Shallow Channel deposit (mean distribution of sands bodies: 4.58 km, mean thickness: 0.6 m, length from 3D lence diagram: 1.58 km), (2) Lower Fan Lobe Sheet ("lean distribution of sands bodies: 2.85 km, mean thickness: 0.08 m, length from 3D fence diagram: 1.26 km), (3) Pelagic Mud, this deposit solely consisting of thick mudstone lithofacies. In term of reservoir potential, the channel deposits have a significant amount of porosity.