Ardjuna

Abstract: Onshore and offshore sub-basins of Northwest Java contain at least ten active petroleum systems which have given rise to more than 150 separate oil and gas fields. The expected ultimate reserves of the region amount to over 4 BBOE, which represents about 14 BBOE in-place. Onshore Java sub-basins within the study area include the Ciputat, Kepuh, Pasir Bungur, Cipunegara/E15 Graben and Jatibarang. Oil and gas originating from these sub-basins have migrated through onshore structural highs, and onward in a northerly direction towards the offshore Northwest Java (ONWJ) region. Petroleum systems located within offshore sub-basins include the South Ardjuna, Central Ardjuna, Sunda, Yani/North Seribu Trough and Asri systems. In this paper, the ten major petroleum systems of Northwest Java have been characterized in terms of the type of source rock migration/carrier bed system, major reservoir and seal units, and style of entrapment. Results from each system are compared and contrasted to account for the relative volumes of hydrocarbons found to date, and the oil versus gas distribution of each system.

Abstract: The Ardjuna Basin, which lies approximately 90 km northeast of Jakarta, is one of a series of hydrocarbon-bearing basins on the southern edge of the Sunda craton that originated during a major Eocene-Oligocene rifting event. The Ardjuna Basin is the name given to a large sag basin located over three precursor rift sub-basins that comprise the Ardjuna rift system: Northern Ardjuna, Central Ardjuna, and Southern Ardjuna sub-basins. The Ardjuna Basin as a whole covers an area of approximately 3000 km2, with each sub-basin comprising an average area of 800 km2. Each sub-basin is comprised of at least one half-graben system and contains, in varying amounts and facies, the primary hydrocarbon source rocks and a major reservoir facies within ARCO Indonesia's Offshore Northwest Java (ONWJ) Production Sharing Contract (PSC) area, the Oligocene Talang Akar Formation. This paper is a review of a geological and geophysical study of the Ardjuna basin as it affected the distribution and character of the Talang Akar Formation. The study utilized seismic, well log, core, and biostratigraphic data of the Talang Akar Formation and older units. Structural depth and isopach maps are used to describe the structural history of these basins and how the timing of graben development effected the accumulation and distribution of hydrocarbon source and reservoir facies. The first prospect developed from this study, the LU-1 well located in the center of the Southern sub-basin, was spudded in February 1995 and declared a suspended oil/gas discovery in May 1995, after testing a cumulative flow of 1400 BOPD and 12 MMCFGPD from three intervals. In addition to the hydrocarbon tests, the well confirmed the presence of a thick, mature, source facies comprised primarily of coals and organic-rich fine-grained sediments in the Southern sub-basin. The presence of these mature source facies confirms that the Southern Ardjuna sub-basin was the likely source kitchen for much of the oil and gas discovered in the Ardjuna basin to date.

Abstract: [Le developpement nauplien de Pseudodiaptomus ardjuna Brehm, 1953, a ete etudie en detail d'apres des eclosions en laboratoire. Cinq stades ont ete trouves, comme dans les autres especes du genre, mais avec une difference portant sur le nauplius II, a symetrie bilaterale. Les nauplii sont aussi compares a ceux de P. euryhalinus et de P. aurivillii., Le developpement nauplien de Pseudodiaptomus ardjuna Brehm, 1953, a ete etudie en detail d'apres des eclosions en laboratoire. Cinq stades ont ete trouves, comme dans les autres especes du genre, mais avec une difference portant sur le nauplius II, a symetrie bilaterale. Les nauplii sont aussi compares a ceux de P. euryhalinus et de P. aurivillii.]