October 2011
Special Focus
Coiled-tubing method drills radial laterals to improve oil production from a depleted reservoir
The North Urtabulak oil field in southern Uzbekistan was discovered in 1972, with 124.2 million bbl of calculated original oil in place. The field is a carbonate reef structure of Jurassic age, with average reservoir thickness of about 320 m (1,050 ft). To date, 119 wells have been drilled on the structure. A reservoir model in 2010 indicated significant volumes of oil in place, much of it trapped between existing wells. This situation was exacerbated by severe near-wellbore damage and pressure depletion in the reservoir. The operator, Tethys Petroleum, had previously implemented horizontal drilling, sidetracking and acid stimulation to access the remaining reserves, but these technologies were no longer considered cost-effective.
