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Generation and 
Migration
of Hydrocarbons from Pre-Tertiary Source Rocks of
the Kamundan Area, West Papua, Eastern Indonesia
By
Ory Sadjati1, N. A. Ascaria1, A. H. Satyana1
(1) Pertamina, Jakarta, Indonesia
The Kamundan area, West Papua, Eastern Indonesia is located to the north of the giant gas field, the Wiriagar Deep, discovered by Arco Indonesia in 1992 within the Jurassic sandstones. This discovery is important for the Kamundan area since showing of how the possible pre-Jurassic source rocks generated and migrated hydrocarbons to the Wiriagar and the Kamundan areas.
To understand generation and migration of hydrocarbons for the Kamundan area,
the expected source formation and the Jurassic reservoirs were mapped. The
source and gas samples from available wells were geochemically analyzed.
Heatflow history reflecting tectonic and source maturation history was generated
using BasinMod - 1D and - 2D softwares. The migration routes of the generated
hydrocarbons then were modeled.
Thermal modeling carried out for Ayot-2, Tarof-2, and Wiriagar-1 wells show
that the sources have been mature since 240-260 Ma (Permo-Triassic). The
maturation of the source is considered to relate with rifting subsidence during
the Triassic. In 210 Ma (Late Triassic), the hydrocarbons have migrated and
charged the whole intervals of the Jurassic reservoirs. Migration kept taking
place and charged the Cretaceous reservoir until tectonic activity of the
mid-Cretaceous uplifted the area and changed the migration
routes. Afterwards,
the hydrocarbons re-migrated along the porous beds at the Cretaceous
unconformity and charged the Late Cretaceous and the Paleocene reservoirs. This
is considered to have caused the significant hydrocarbon accumulation in the
Paleocene reservoirs. The study concluded that the petroleum system of the
Kamundan area is Permo-Triassic, Jurassic and Paleocene.