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The AAPG/Datapages Combined Publications Database

Indonesian Petroleum Association


29th Annual Convention Proceedings (Volume 2), 2003
Pages 1-17

The State of the Art Finding New Oil and Gas Reserves in an Old and Mature Area, Offshore Northwest Java Sea

Sudarmono, Sugeng Herbudiyanto, Toriq Abdat


After more than 30 years exploration and production, finding new oil and gas pools in the Offshore Northwest Java (ONWJ) Basin becomes more difficult. Drilling cost and project economics are the primary considerations. The remaining identifiable prospects in ONWJ are commonly small and far from the existing facilities. Well integrity, drilling technology, available rig contracts and safety issues are other constraints to tap oil and gas from the subsurface. The selection and prioritization of drilling candidates is also affected by market demands.

For example, around 15 years ago, Parigi carbonates were neglected as exploration targets because they contain only gas. With the increasing gas demand in Java, Parigi carbonates become primary drilling targets. Exploration success in Parigi carbonates is generally less than 30 %. Commonly the thick Parigi carbonate buildups only contain thin gas columns at the top, although one accumulation has more than 200 feet of gas column and holds in excess of 1 TCF gas reserves. Besides reserve sizes, distance to an existing platform is critical from drilling point of view because Parigi carbonates are shallow.

In such mature oil fields like in ONWJ, without a new technol ogy breakthrough, an extraordinary effort is required to identify new hydrocarbon pools. The oil and gas reserves within channel-type sandstones of Talang Akar Fm. for example, have not yet been fully developed due to inability of seismic technology to image the sandstones. In a few cases, thorough integrated evaluation incorporating all available data, application of strong basic hydrocarbon exploration concepts, creativity and solid and integrated multi-disciplinary teamwork has identified of new remaining oil and gas pools in ONWJ. Utilization and integration of seismic attributes, near and far seismic traces and Direct Hydrocarbon Indicator (DHI) helped to identify remaining gas pools in some cases.

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