Abstract

The Belida Oil Field was discovered in December 1989 with the Alu Alu E-1 well. The Belida Field contains estimated reserves of 187 million barrels of oil and 130 BCF of gas. It is in the western part of South Natuna Sea Block B Production Sharing Contract Area. Average water depth is 250 feet. The Belida structure has four-way dip closure and is bounded by a fault along the southern flank. The structure formed as a result of structural inversion of a half-graben during Early Miocene regional compression. The sedimentary section which overlies Cretaceous granitic basement ranges in age from Oligocene to Holocene. The principal oil reservoirs are the Oligocene Udang and Early Miocene Lower Arang Sandstones. Three main gas reservoirs are present in the Early Miocene Arang Formation. Sands of the Udang Formation represent a series of stacked fluvial channels characteristic of a low relief distributary channel system. The Lower Arang sandstones represent distributary mouth bars within a progadational lacustrine deltaic setting. The sand continuity, porosity and permeability are good across the field. Well tests support good vertical and lateral reservoir continuity. Petrophysical evaluation indicates that the reservoir sands have around 30 percent porosity and up to several Darcies permeability. Electric log evaluation and RFT pressure analysis support a flat oil/water contact across the field in both the Udang and Lower Arang reservoirs.