Petroleum geology of the area offshore of the Malaysian states of Sarawak and Sabah in Northwest Borneo is discussed. Exploration activities have centered in this area for the past 20 years. Drilling activity over the past decade has led to the discovery of two large oil fields, six large gas fields, and several smaller oil fields.

The geological framework and evolution of the East Malaysian shelf is discussed, along with comment on basement rocks, the Northwest Borneo geosyncline (Cretaceous-Paleogene), middle Tertiary rifting, tectonics, and facies (Neogene) analysis.

Three giant oil and gas fields are examined: the Baronia field, Samarang field, and the Central Luconia field. Discussions include material about location, stratigraphy, structure, hydrocarbon reservoirs, and development to date.

A final section highlights petroleum generation and trapping mechanisms in the East Malaysia area.