Implementing CHOPS in the Karazhanbas Heavy Oil Field, Kazakhstan

The Karazhanbas Field (KBM) is a giant shallow heavy oil field in western Kazakhstan, less than 460 m depth. It contains heavy oil (μ ~400 cP) in seven reservoir zones from several to 40 m thick in unconsolidated sands with porosities 28-32%, permeabilities of ~0.5 D, and an arkosic lithology with angular grains. There is no free gas cap, and the structure is divided into fault-controlled blocks, some with active water, others not. Starting in 2000, Nations Energy Company Limited initiated cold heavy oil production with sand (CHOPS) in new areas on the flanks of the developed central part. PCPs are used to lift the oil, and sand is allowed to enter into perforated zones. Production of 6,000 m/day was reached by January 2004, an increase of over 4,000 m/d within 4 years. Sand flux is far lower than Canadian cases because of low oil viscosities; water flux is higher due to higher water mobility and active flank water. We describe the geological setting of KBM, reservoir and petrophysical properties, and other geological information. Typical sand-oil-water production is documented, and well behaviour is contrasted with Canadian cases. CHOPS is an economic success at KBM, allowing recovery factors of 8-15% from zones as thin as 3-10 meters, for which thermal technologies are not economically viable. It is planned that in the thickest zones CHOPS will be followed by steam stimulation to take advantage of the enhanced permeability and compressibility generated by the CHOPS process.