ANALISA SIKUEN STRATIGRAFI UNTUK MENDEFINISIKAN CEBAKAN STRATIGRAFIS DI CEKUNGAN ASRI BAGIAN UTARA : RESERVOIR BATUPASIR ANGGOTA ZELDA BAWAH

• Main Author: Felantika Effendi Rizal, Yudhi
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/73127
• Institution: Institut Teknologi Bandung

Asri Basin is located 180 km offshore to the north of Java coastline and 140 km offshore to the east of Southeast Sumatra coastline with 20 to 25 meters water depth. Finding new discoveries in deep reservoir is an exploration challenge in Asri Basin. Lower Zelda Member, defined as deep reservoir deposited in Asri Basin. This Eocene-Oligocene Lower Zelda Member is the oldest member in Talang Akar Formation. Limited structural trap in this interval has lead to develop stratigraphic trap concept. Sequence Stratigraphy study was done to help defining stratigraphic trap in this area. Formation Micro-Imaging (FMI) data combined with wireline log and drilling sample information are used to define parasequence bounding surface, lithofacies and facies associations. There are four facies associations and thirteen lithofacies identified in Lower Zelda Member. First facies association, fluvial channel, consist of lithofacies massive sand (Sm), tabular cross-bedded sand (Sb), through cross-bedded sand (St), laminated sand (Sh), ripple cross-bedded sand (Sr), dewatered sand (Sd), and massive shale (Fsm). Second, levee, consist of lithofacies heterolitics (Ht) and slump heterolitics (Hd). Third, overbank, consist of lithofacies paleosol (P), massive shale (Fsm), shale laminated (Fl), shale with root-bed (Fr), and shale clast-conglomerate (Gsc). Forth, crevasse splay, consist of lithofacies massive sand (Sm), tabular crossbedded sand (Sb), through cross-bedded sand (St), laminated sand (Sh), ripple crossbedded sand (Sr), and dewatered sand (Sd). Furthermore, interpreted system tract and sequence unit has lead to four sequence boundary (SB) and three correlative conformity (CC). Based on corelated sequence unit, three sand units are interpreted within Lower Zelda Member: LZA, LZB, and LZC. Sand Reservoir unit countered in Manik wells has limited connectivity. This condition confirms that Lower Zelda Member is an isolated fluvial channel system and the facies are changing very rapidly. Lateral depositional reservoir model, generated from extracted coherence attribute, showed a good agreement with the geological information from image log data. Structure and seismic attributte map shows that stratigraphic trap is a combination of facies change, structural dipping and faulting.