Abstract

Total ultimately recoverable petroleum resources discovered to date in SE Asia and Australasia amount to around 50 billion barrels of oil and condensate and 450 trillion cubic feet of gas. These resources are reservoired in over 2,000 separate oil and gas fields, located in eleven countries. There are at least 50 giant fields and 100 productive petroleum systems in the region. Stratigraphic ages of source rocks, reservoirs and seals span 500 million years from the Paleozoic to the Pliocene. Paleogene source rocks account for over 50% of discovered petroleum resources.

Petroleum systems in the region have been fundamentally controlled by global tectonic events. The majority of Australian-New Guinea-New Zealand petroleum systems are genetically linked to Late Paleozoic-Mesozoic rifting of the Australian continental margin associated with the breakup of Gondwanaland. The majority of SE Asian petroleum systems formed during Tertiary extrusion tectonics and back-arc extension associated with the convergence and collision of the Indo-Australian and Eurasian plates. Systems in the Philippines and northern New Guinea are related to the more complex interaction of the Philippine Sea and Pacific plates with the Eurasian and Indo-Australian plates.

Source rocks include lacustrine, fluvial-deltaic, marine and marine carbonate facies. Oil-prone coals are particularly significant in some systems, while several shallow systems rely on bacterially-generated (biogenio) gas for charge.

Reservoirs range from lacustrine, fluvial-deltaic, paralic, and marine sandstones, through alluvial fans, turbidites, and massive carbonate bioherms, to less conventional fractured volcanics, volcaniclastics, and hydrothermally altered granites. Seals are generally mudstones; evaporites do not play an important role in the region's petroleum systems.

Using typical ranges of migration and trapping efficiencies, the total amount of oil and gas released from source rocks within the region's petroleum systems could range to over fifty trillion BOE.