Abstract: The oil rings with condensate gas cap in China are found to be relatively small, with only about several millions of tons of reserves. For the oil ring is generally narrow, it is relatively difficult to drill just into it, and there are few oil-rim wells. Such brings difficulties for evaluation of this kind of reservoir development. Especially, the calculation of reserves can hardly be made. Because of very low reserve-production ratio(only about 5: 1) for black oil in Southwestern Tarim basin, this paper made an evaluation of Xiqi' eroil ring in Kekeya field, a difficult developed small oil ring, and found out a set of methods used for estimation of small oil ring reserves, called net pay thickness extrapolation. Also, this paper suggested that using orientational strati-penetrating horizontal drilling technology can improve the producing reserves.

Key words: Kekeya, condensate field, oil ring, reserve, horizontal well