インドネシア・東ジャワにおけるバイオジェニックガスの探鉱開発

抄録

Many biogenic gas accumulations are distributed continuously in the offshore of East Java, from the Madura Strait to the south of the Kangean islands. New gas discoveries have continued until recent years, and are all of the same play type of limestone and sandstone reservoirs of the Pliocene Mundu/Paciran formation. Gas production in East Java was dominated by thermogenic gas until the early 2000ʼs. However, this has recently been replaced by biogenic gas in response to high gas prices caused by increasing demand and the accelerated development of small to mid-size gas fields brought about by synergies created by the presence of infrastructure such as the East Java Gas Pipeline.

As most of the biogenic gas fields discovered to date are at depths shallower than 1,000 meters sub-seabed, they are accompanied by DHIs （Direct Hydrocarbon Indicators） such as ?at spots, and are easily detected as anomalies in the seismic data, which is generally of good quality. Multiple ?at spots are clearly recognized at the reservoir horizon and overlying shallow layers in the seismic data. The flat spots correspond to shallow gas and paleo-GWC, and in cases where a gas field is discovered, shallow gas and multiple DHIs are identi?ed without exception.

In the development of these biogenic gas fields, an optimized production system was adopted, taking into consideration geological conditions such as the shallow reservoir depth, closure area and size and the distance between accumulations, and production systems such as subsea completion with FPU (Floating Production Unit), or cluster development with individual wellhead platforms were deployed. After the development of gas fields close to consumption areas and shallow in depth are completed, it is expected that exploration and development activities will shift to more remote and deeper areas.