Publications

Discovered in 1974, Nilam Field is a mature gas field at the apex of the Mahakam Delta, consisting of Middle to Upper Miocene fluvio-deltaic reservoirs. Hydrocarbon accumulation is structurally trapped, with stratigraphic traps dominating the flanks. As of Q1 2025, 367 wells have been drilled, with 63 wells currently producing. The field contains stacked deltaic reservoirs divided into four main productive zones (D, E, F, and G). Reservoirs mainly comprise distributary channel sandstones and delta-front mouth bars, with porosity ranging from 8% to 30% and permeability reaching several hundred mD. Both channel and delta front bar orientation mainly from west-southwest to east-northeast.

The G Zone, the deepest productive zone, faces production challenges due to compaction and reduced pore space from burial depth and diagenetic processes. Thin-section, SEM, and XRD analyses indicate a complex diagenetic history, including siderite crystallization, kaolinite/chlorite precipitation, silicification, and quartz overgrowths.

Core from well NLM-179 (drilled in 1999) was taken from the G zone, specifically from the G55B and G56A reservoirs. The 67 ft (13,050–13,117 ft MD) core reveals a prograding deltaic system. A multi-storey distributary channel sandstone with coaly pebble-sized lag deposits overlies highly bioturbated delta front bar deposits, separated by short swamp or tidal flat intervals.

Facies-based reservoir modeling, integrating core synthesis, log interpretation, and analog outcrops, helps to optimize low-quality reservoirs (LQRs), commonly found in bioturbated delta-front bars, crevasse splays, channel levees, and abandoned channels. Understanding burial history and diagenetic processes enables better reservoir management, improving recovery and extending field life.