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East Indonesia: Plays and Prospectivity of the West Aru, Kai Besar and Tanimbar Area-Identified from New Long Offset Seismic Data
(1) Spec Partners Ltd, Bedford, United Kingdom.
(2) Far Cape Pte Ltd, Singapore, Singapore.
(3) MIGAS, Jakarta, Indonesia.
This paper is based on an analysis of >8000 km of new 2D seismic data (10,000m cable) in Eastern Indonesia west of Aru Island, acquired as a multi-client survey run under the jurisdiction of MIGAS.
The E/SE portion of the survey covers part of the Arafura Platform, whilst its W/NW portion covers the Tanimbar and Aru Troughs and the eastern part of the Banda Arc.
The area is Frontier in nature but is on trend with a number of large fields: multi-TCF Abadi and Tangguh gas fields. It is relatively unexplored, with the 3 dry wells - Koba-1 (‘84) & Barakan-1 (‘95) offshore on highs in/around the Aru Ridge and Kai Basar 1 ('96) drilled on the island encountering thick Mesozoic.
The major discoveries in the region lie both to the north and SW of the survey area where the Jurassic Plover Sandstone petroleum system is proved in the Tangguh and Abadi fields; and also further westwards (in Sunrise, Evans Shoal, Troubadour and Bayu Undan). In this petroleum system, the gas/condensate fields are thought to be charged from equivalent aged deeper lying Plover formation source rocks.
In the survey area, Jurassic reservoirs are expected to occur both on the western margin of the Arafura Platform (west of Aru and the Aru Ridge, where the Mesozioc section thickens rapidly) and in the western part of the survey area where the seismic data off Tanimbar and around the Kei islands show burial below a Neogene aged melange associated with collision tectonics making up the eastern margin of the islands. (Similar to that seen off Seram and East Timor).
Paleozoic (as well as Mezozoic) development has been reported south of the island of Aru (in/around the South Aru Graben). The Paleozoic petroleum system is believed to be analogous to that seen in parts of the Bonaparte Basin and Goulburn Graben, and is evidenced by the presence of deep basins, such as the Barakan Basin, which are possibly filled with several thousand metres of Cambro-Ordivician to late Devonian/Early Permian sediments.
A number of different plays have been recognised in the survey area - these are defined by their relationship to the main structural/stratigraphic provinces:
Tertiary: within Melange i.e East of Tanimbar/Kei;
Jurassic: Sub-Melange, Platform Margin West and Southwest of Aru, South Aru area;
Paleozoic: Grabens in the Arafura Platform e.g Barakan Basin.
The potential of these petroleum systems are illustrated with numerous PSTM seismic sections from the new survey.