Evaluation and Modelling of Coal-Driven Petroleum Systems from Tertiary Basins of Offshore Malaysia

Peter Abolins¹ and Wan H. Abdullah^2
1PETRONAS Carigali Snd Bhd, Kuala Lumpur, Malaysia
²Department of Geology, University of Malaya, Kuala Lumpur, Malaysia

The Sunda shelf of Southeast Asia is home to numerous prolific hydrocarbon basins primarily of Cenozoic age. Due to the progressive tectonic evolution of Sundaland during the Cenozoic, the petroleum systems that developed fall into three main types: a lacustrine system, developed generally during extensional phases; a paralic/fluviodeltaic system, developed generally during passive phases; and a deepwater system developed in deepwater margins of Sundaland.

Producing basins in Malaysia possess one or more of these petroleum systems. This paper is focused on the paralic / fluviodeltaic petroleum system of two such basins in Malaysia, the Malay Basin and the Balingian Province (part of the Sarawak Basin).
An important component of the paralic / fluviodeltaic petroleum system are the organic rich, extensive coal seams and related carbonaceous shales. Onshore studies of the coals in the Balingian Province show that they are laterally extensive, although generally no more than 1m in thickness. The Malay basin is entirely offshore and so no coal outcrops can be studied although logs indicate they also tend to be no more than 1m thick and can often be widely correlated.

Detailed organic petrology and geochemistry have been used to differentiate two end member coal types: a freshwater, “typical” peat swamp coal and a marine influenced ”mangrove” coal. Fingerprinting of oils from the Malay basin and Balingian have allowed positive correlations to these coals to be made.

Vitrinite reflectance analysis of the coals, particularly of the gas prone coals (shales and oil prone coals may show suppressed reflectance values), have been useful for calibrating basin models. Modelling hydrocarbon generation, for timing and volumetric estimates of the quantities of oil and gas that can be generated from these coals, are currently underway and are described.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery