Abstract

The purpose of this study was to evaluate miscible recovery of oil by carbon dioxide, using both secondary and tertiary processes.

Two types of oils of different compositions from different reservoirs were considered. They were stock tank oil from Kawengan field, Cepu, East Java, and recombined oil from one of the East Kalimantan fields.

The experiments were carried out under miscible condition of pressure and temperature, i.e. at 2300 psig (158.6 bars) and 131°F (55°C) for the Kawengan stock tank oil, and at 3900 psig (268.9 bars) and 212°F (100°C) for the East Kalimantan recombined and stock tank oils.

The core used for these experiments was unconsolidated sandpack of 1.5 cm diameter and 2 m long. From the experiments, the following conclusions can be drawn:

a). The CO₂ miscible flooding is capable of recovering more than 90 percent of the oil whether the process is applied as secondary or tertiary recovery.

b). The presence of solution gas in the oil tends to reduce the oil recovery of CO₂ injection.