Litofasies studies and Maturity Levels of Ngrayong Deltaic Sandstone, Tawun Formation Jamprong Region, Kenduruan District, Tuban and Its Implications for Reservoir Quality


Ngrayong Sandstones member of Middle Miocene Tawun
Formation, is one of the main reservoir in the North East
Java Basin. Currently depositional environment of
Ngrayong Member is still being debated, because in Cepu
area and surrounding sediments with relatively similar
characteristics can be interpreted into two different
environments are deltaic and deepwater turbidite. The
difference being the object of interest to be discussed
related to hydrocarbon reservoir potential.
The integrated research methods are surface geological
mapping, measured stratigraphic column, granulometry
analysis (spericity, roundness, composition, grain size and
sorting variations), petrography, porosity and permeability
Litofacies unit in the mapping area are Facies of Shale with
Sandstone Intercalation, Coal and Gypsum Fragments,
Sandstone Facies, Siltstone Facies, Interbeding Sandstone –
Siltstone Facies, and Red Sandstone Facies. Sedimentary
structures such as bedding fisillity, bedding, bicurrent
crossbedding, oscillation ripplemark, flaser, lenticular
bedding, coarsening upward. Petrographic analysis of red
sandstone shows types of sandstone such as Arenite Quartz,
arkosic Wacke until Sub Arckose. Granulometri analysis
shows sortation ranged from poorly – moderately, level of
roundness and sphericity are low sphericity with a little
clay content, showing a level of maturity from submature
until mature which was deposited with medium energy.
Porosity and permeability test of Sandstone facies result
porosity 32% -44% with permeability-833 mD – 0.015
mD, and Porosity and permeability test of Red Sandstone
facies result porosity 32% -41% with 90 – 404 mD
permeability. Based on an integrated analysis of
sedimentology known that many facies was deposited in
Pro-delta environment and Delta Front. The most excellent
reservoir quality are the Red Sandstone facies and
sandstones facies with good porosity and permeability
which are interpreted as part of mouth bar from deltaic
Keywords: Ngrayong, Delta, Sandstone