This paper presents the importance of horizontal wells for increasing the sweep efficiency and improving the oil recovery in a low-permeability sandstone reservoir based on the geological characteristic and production performance of L60 reservoir of the Huizhou 26-1 oilfield. And also discusses the production performance and developing effects of two horizontal wells. bearing characteristic is not good due to the effect 1. RESERVOIR GEOLOGICAL of calcite cementation.

CHARACTERISTICS The oil property of the L60 reservoir is paraffin-The Huizhou 26-1 oilfield is located in Pearl base crude oil with low density, low viscosity, high River Mouth Basin of the South China Sea. The wax content, high freezing point and low sulfur water depth is 110 meters. This oilfield has content. The average oil density is 0.822g/cm3, the multiple reservoirs consisting of medium to coarse sulfur content is 0.18%, the wax content is grained sandstone interbedded with streaks of 20.37%, the freezing point is 27°C, and the oil shale and each reservoir is separated from the viscosity at reservoir temperature and pressure is other reservoirs by shale intervals. There are nine 2.31mPas. reservoirs in this oilfield, of which five main reservoirs (L30, L40, L50, M10 and M12 2. PRODUCTION PERFORMANCE reservoir) with good reservoir properties and four non-main reservoirs (K08, K22, K30 and L60 OF L60 RESERVOIR reservoir) with poorer reservoir properties. The Huizhou 26-1 oilfield is put into production The L60 reservoir is a low-permeability in Nov. 1991 with 16 conventional wells. sandstone reservoir with edge water drive. It is a According to the overall development program, drape anticline structure developed on the the main reservoirs are M10, M12, L30, L40 and basement. The oil-bearing area is 14.6km2 and its L50, other reservoirs are of non-main ones and OOIP is 436×104m3, being equivalent to 9.6 served as production replacement layers and percent of the total OOIP of the Huizhou 26-1 potential stimulation candidates. oilfield. During the later production period, the two The L60 reservoir belongs to the Zhujiang sidetracking wells with horizontal interval were Formation of the lower Miocene. Its sedimentary drilled to improve the development effect of L60 facies is river mouth bar deposit of delta front. The reservoir as well as that of the Huizhou 26-1 sand body distribution is controlled by the oilfield. And using this technology, the producing structure. The reservoir formation is thin although reserves and development effect of L60 reservoir it becomes thicker in the south-east side. The with low permeability have been greatly improved, reservoir thickness is about 30m,

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