Abstract:

The reservoir of Liuhua oilfield, which belongs to Zhujiang Formation, is a typical Neocene platformrim reef located on the margin of carbonate platform of Dongsha Massif in Pearl River Mouth Basin, South China Sea. There are 7 types of rocks, including crusty algal boundstone, twined algalcoral framestone, foraminifer and algal grainstone and rhodolite reef limestone. The reservoir spaces include 7 types of pores and 4 types of fractures. The main pores include primary intergranular pores, pores in algal frames, intragranular dissolved pores, cavity pores and intercrystalline micropores. The main fractures include dissolution fractures, interlayer fractures in crusty algal boundstone, and stylolite dissolved fractures. The reservoirs are classified into four types, including porecavernfracture type, pore type, fractureporecavern type and fracture type. Crusty algal boundstone belongs to porefracture type reservoir. Mieritic grainstone and rhodolite reef limestone are pore type. Coral framestone belongs to fractureporecavern type. Fracture type includes sparry grainstone and relatively heavily cemented algal boundstone. Sedimentary microfacies and diagenesis control the distribution of different types of reservoir. Multiple exposures during the formation of reef have great influence on the reservoir. The sedimentarydiagenetic evolution of reef reservoir can be divided into four periods, including early reef formation and early exposure period, late reef formation and minor exposure period, reformation period during the early burial, two stages of reservoiring and groundwater dissolution periods. The spatial distribution of reservoir types are predicted according to the sedimentarydiagenetic evolution.

Key words: Neocene, reef, platform margin, reservoir space, genetic analysis, sedimentationdiagenetic evolution