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ABSTRACT: Low-resistive reservoirs in the Miocene Mahakam Delta deposits in East Kalimantan

Partono, Yoseph J.1, Arthur S. Trevena2 , (1) Unocal Indonesia Co, Balikpapan, Indonesia (2) Unocal Corp, Sugar Land, TX

Low-resistive sandstone reservoirs are major contributors to oil and gas production in East Kalimantan. These reservoirs are found in Attaka, Serang, Melahin, Kerindingan, and Sepinggan fields. They represent depositional environments including fluvial channel, distributary channel, distributary mouth bar, delta front bar, prodelta, and shallow marine.

Dispersed and laminated clays of various origins are the major cause for low resistivity. Thick, hydrocarbon-bearing, Upper-Miocene, fluvial channel deposits in Attaka, Melahin, Kerindingan, and Serang fields exhibit low resistivity due to abundant dispersed, authigenic smectites that line pores. Tidal clay drapes and dispersed clay due to bioturbation have caused low resistivity in tidal distributary and distributary mouth bar sands in Attaka, Serang and Sepinggan fields. Shoulder-bed effects have further reduced the resistivity of shaley, thin-bedded delta-front and prodelta sands in Attaka, Serang, and Sepinggan fields.

These shaley and thin bedded sandstone reservoirs are difficult to interpret and complete, but by using the right technology Unocal has successfully produced significant amounts of oil and gas from this type of reservoirs.

Low-resistive sandstone reservoirs may be easily overlooked in exploration and development wells. However, geoscientists can recognize them by integrating data from high-resolution wire-line logs, mud logs, and core. Low-resistive pay may change the economics of a prospect, or in some cases, low-resistive plays may evolve into prospects themselves.

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