ABSTRACT: Reservoir heterogeneity of Miocene deltaic sandstones from Attaka and Serang Fields, Kutei Basin, offshore E. Kalimantan, Indonesia

Trevena, Arthur S.¹, Yoseph J. Partono², and Tom Clark²
(1) Unocal Corp, Sugar Land, TX
(2) Unocal Indonesia Co, Balikpapan, Indonesia

Heterogeneous sandstones of the upper to middle Miocene Lobe of the Mahakam Delta are prolific hydrocarbon reservoirs in the northern Kutei basin. At Attaka and Serang fields, more than 620,000,000 barrels of oil and 1.3 trillion cubic ft of gas have been produced from sandstones, that we interpret as delta front bars and tidal/fluvial distributary channels. Sand bodies of the modern Mahakam delta are analogs for many of these reservoirs.

Delta front bars are burrowed to laminated, fine-grained sandstones that form equant to somewhat dip-elongate bodies that range in thickness from 2 to 15 ft and may exceed several miles in width. Cross-stratified, coarse- to fine-grained tidal/fluvial distributary channel sandstones are 10 to 50 ft thick and narrow (< 1 mile wide).

Distributary channel sandstones are typically highly porous (20-35%) and permeable (100-10,000 md), although tidal distributaries exhibit permeability heterogeneity, due to mud drapes and local burrows. Delta front sandstones, although areally extensive, have generally poorer reservoir quality than the distributary channel sandstones (k=< 0.1 - 1000 md; porosity=10-30%). Also, the delta front sands exhibit major cm- to dm- scale variations in permeability, that are related to variations in clay content and intensity of burrowing.

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