Abstract

Geochemical studies conducted in Asamera's Block "A" in the North Sumatra Basin concluded that several intervals retain the capability to generate hydrocarbons. The maturity level of the rock samples suggests that the top of the oil window generally occurs in the middle part of the Baong Formation and that the deepest parts of the sections penetrated by the deepest wells have reached a generation stage close to or beyond the end of oil generation. Total organic carbon measurements indicate generally lean to moderate amounts of organic matter, with higher levels of organic matter restricted to particular intervals. The distribution of the type of organic matter shows that in the eastern part of Block "A" the kerogen is characterized by an abundance of land derived organic material. The amount of sapropelic organic matter, indicating a more marine influence, increases toward the western part of the study area. Such a distribution may relate to the influx of land derived organic matter from an eastern land mass located in the area of the present-day Malacca Straits.

Oil analysis of samples from six different fields, and taken from both Keutapang and Seureula Formation reservoirs, indicates typically non-waxy paraffinic oils with API gravities ranging from 49.2° to 59°. From oil correlation studies it is concluded that the crude oils have a common origin which was probably fine grained marine sediments of the Middle to Late Miocene Baong Formation.