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ABSTRACT: Tectonic evolution of the south Mahakam area and its petroleum implications

Gangui, Alfredo1, Thierry Rosaz2, Bernard Lambert3, and Dominique Roy1
1) Total Indonesie, Balikpapan, Indonesia 
(2) Total Nigeria, Paris la Defense, France 
(3) TotalFina, Paris la Defense, France

The southern part of the Mahakam PSC is located near the southern margin of the KUTEI Basin, offshore eastern Kalimantan Indonesia.

From Early Eocene until early Upper Miocene, this area has been influenced by extensional stresses, with the development of a series of NW-SE (transtensional?) normal faults (Maruat, Sesumpu and Sepinggan faults) separating the basin from the Paternoster Platform to the SW, and forming the primary structural framework of the area. The structures developed during this period vary in orientation from NW-SE, associated to the main faults, to E-W, probably related to a partial strike-slip component. Also during this time secondary N-S trending normal faults developed (e.g. Mandu, Metulang), which were allied to the main fault systems. During the Upper Miocene-Pliocene, the whole area was affected by a regional compression (N150-170), inducing a dextral strike-slip reactivation of these main normal faults.

The petroleum system of the area has a strong structural component with most of the hydrocarbon accumulations occurring along these fault systems (Sesumpu-Sepinggan), which provide the main migration pathways. The play types are related to structures associated with two different tectonic phases: a) Middle Miocene tilted (growth-) fault blocks (METULANG field). Upper Miocene-Pliocene dextral strike-slip deformation : b) reactivation of early tilted faulted blocks (MANDU structure), and c) development of "en-echelon" folds (JUMELAI field).

Up-to-date 3D seismic interpretation techniques, including coherence and PSDM processing, were used to define these prospects, successfully drilled by TOTALFINA during the 1998 exploration campaign.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia