Print this pageKarachaganak Field, Pricaspian Basin, Kazakhstan
BODDEN, W. RUPERT, III, GRIGORI X. SHERMAN, TOROCHEL A. YUGAI, VALERI A. SAVVIN, and EDGAR S. VOTSALEVSKY
Karachaganak Field is located on the northern margin of the Pricaspian Basin, 150 km east of Uralsk, Kazakhstan. The discovery well, drilled in 1979, tested a seismically-identified structural high. The field comprises three carbonate complexes: late Devonian to early Carboniferous (400 m thick), early to middle Carboniferous (750 m), and early Permian (900 m). The complexes are separated by unconformities and associated condensed sections, marked by shales. The early Permian section is developed largely in the eastern half of the field, where it forms a steep-sided reefal buildup. The total gas column, encompassing Permian and Carboniferous strata, reaches 1420 m at the thickest; the oil column within Carboniferous and upper Devonian strata is 200 m. Net pay per well averages 200 m gas and 45 m oil. Reservoir porosities average 9 to 10 percent. Although median permeability measured from core is only 1 millidarcy, the best reservoir rocks are seldom recovered and can range from 400 to 1700 millidarcies.
Estimated original in-place reserves are 51.2 TCF gas, 6.9 billion bbl condensate, and 7 billion bbl oil. Ultimate recovery will depend upon the success of pressure maintenance during production.
Additional pools have been discovered in underlying middle Devonian (oil) and overlying Filippovian strata (gas condensate).