GENERAL GEOLOGY OF KATI FORMATION IN SERI ISKANDAR WITH EMPHASIZES ON SEDIMENTOLOGY, PETROGRAPHY AND RESERVOIR POTENTIAL

Kati Formation found in Seri Iskandar is the extension of the same formation from Kuala
Kangsar. This study emphasize on the sedimentology, petrography and reservoir potential of
Kati Formation in Seri Iskandar vicinity which deposited during Carboniferous to Permian
period. Lithology recorded at the outcrop consist of sandstone and mudstone with three
type of facies identified. Facies 1 is massive sandstone, characterized by structureless
deposit, amalgamated and thickness varies from 1m to few meters thick. Facies 2, deposited
by suspension method within long period of time is thick bedded mudstone. Interbedded
sandstone and mudstone is the Facies 3 based on sedimentological analysis, deposited by
high density low turbidity current. This three facies are associated with channel-levee
deposit. From the analysis conducted, it is believed that this sediment deposited at the
inner part of submarine fan. Five thin sections had been produced to analyze mineral
composition of the rock samples collected from the outcrop. The main mineral found is
quartz followed by rock fragment. Feldspar, which usually can be found abundantly in
sandstone sample is absent due to the chemical weathering process that took place. From
the point counting method conducted, sandstone sample from Kati Formation in Seri
Iskandar is grouped into litharenite group, based on Folk Classification. Porosity is the aspect
of reservoir potential which had been measured by impregnate thin section produced with
blue dye. The average porosity value obtained is 24.4%. Regardless of other reservoir
character, this sandstone can be concluded as potential reservoir.