CARBONATE RESERVOIR COMPARISON BETWEEN TAHE OIL FIELD AND PUGUANG GAS FIELD

Great breakthroughs have been made in ChinaGs carbonate rocks exploration for oil and gas in recent years with the discoveries of such large-scale oil and gas fields as Tahe oilfield and Puguang gasfield. Basic features of reservoirs, diagenesis, and controlling factors of Tahe oilfield and Puguang gasfield are discussed and compared systemically in this paper. Reef (shoal) reservoirs on the platform margin are usually in good quality as porous or fractured-porous reservoir type with low heterogeneity. Weathering crust karst reservoirs are usually in bad quality, as pore-hole-fracture complex reservoir type with high heterogeneity. Dolomitization is an important mechanism for the forming of super-deep (> 6000 m) carbonate reservoirs, resulting an average porosity increase of 3.5%~4.0%. Thermochemical sulfate reduction (TSR) reactor plays an active role in alteration of reservoir, but it may not meliorate reservoir properties greatly. Tectonism and depositional facies are the main factors controlling the reservoir physical properties of Tahe oil field and Puguang gas field. Depositional facies controlled reservoir quality by affecting rock solubility and water permeability in weathering crust karst reservoir, or by affecting lithology and physical properties in reef (shoal) reservoir on the platform margin. Tectonism controlled the distribution and intensity of weathering crust karst reservoir, while multi-stage structural fractures improved the reservoir physical properties of reef (shoal) reservoir on the platform margin.