ABSTRACT: Deepwater Depositional Facies and their Reservoir Characteristics, West Seno Field, Offshore East Kalimantan, Indonesia

Saller, Arthur¹, Trevor Brown², Richard Redhead², Hans Schwing², and Jossy Inaray²
(1) Unocal Corporation, Sugar Land, TX 
(2) Unocal Indonesia, Balikpapan, Indonesia

Approximately 900 feet of core have been recovered from Upper Miocene deepwater strata between 7500 and 8800 feet in West Seno Field, offshore East Kalimantan. Approximately 240 feet or 27% is sand. Most of the sands appear to have been deposited in a middle to upper slope environment in a series of aggrading channel-levee complexes during lowstands of sea level. Sands are dominantly fine to very fine-grained and poorly to very-poorly sorted. Bed thicknesses range from less than 1 mm to approximately 6 feet. Reservoir characteristics are related to depositional facies. Massive sands have the best reservoir characteristics (average porosity of 29.3% and permeability of 630 mD). These appear to have been deposited as channel-fills and/or splay deposits. Horizontal current-laminated sands have average porosity of 26.6% and average permeability of 301 mD. Rippled sands have lower porosity and permeability (average of 24.8% and 147 mD, respectively). Intervals dominated by laminated to rippled sand with minor shale are characteristic of proximal levee environments. Intervals with shale and thin rippled sands are interpreted as distal levee deposits. Thin-bedded sands (1-5 cm thick) have still lower porosity and permeability (16-24% and 5-200 mD, respectively). "High resistivity" or "terrigenous" shales containing very thin silt and sand laminae are interpreted as lowstand overbank deposits. Massive to burrowed, "low-resistivity" or "hemipelagic" shales are widespread and interpreted as transgressive and highstand deposits. Very thin sheets of coaly fragments are locally abundant immediately overlying and within sand beds. Features characteristic of thick, widespread sheet sands were not observed.

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