Abstract: The deep-ultra-deep carbonate reservoirs in the Tarim Basin have already formed a production base of 3 million tons of oil, but there is still controversy over the types of reservoir space and the structural differences of reservoir bodies in deep-ultra-deep carbonate rocks, which affect the optimization of oil and gas reservoir development schemes. Based on field outcrops, cores, seismic, logging, drilling and production data analysis, we conduct a comparative study on the types and structural differences of high-quality carbonate reservoir space and reservoir bodies in the Ordovician deep-ultra-deep strata of the Halahatan-Fuman Oilfield. The results show that: 1) Halahatang-Fuman Oilfield is controlled by the weakening of atmospheric freshwater dissolution from north to south: the main reservoir space types in the northern anticline karst area are karst caves and dissolution pores; the main reservoir space types in the southern interbedded karst area of Halahatan are fractures, pores, and cavity-type reservoirs and karst rivers; the main reservoir space types in the Fuman fault-controlled karst area are angular breccia intercavities and fault voids, and structural fractures. 2) The differences in reservoir space filling characteristics are also quite obvious: the karst caves in the northern anticline karst area and the interbedded karst area of Halahetang are relatively rich in dissolution filling, mainly including sedimentary filling materials, collapse filling materials, and chemical precipitation filling materials; however, the filling characteristics of the reservoir bodies in the Fuman Oilfield are relatively simple, mainly composed of calcite and silica cementation. 3) The differences in the internal structural features of reservoir spaces are as follows: the northern karst area has three layers of dissolution structures, namely, the surface karst belt, the percolation karst belt, and the subterranean karst belt; the southern interbedded karst area of Halahetang has three structural elements composed of the supply area, the percolation belt, and the discharge area; the fault-controlled karst area has four structural models, namely, the single sliding surface structure, the compressional nucleus belt structure, the tensile-torsional cavity nucleus belt structure, and the grille-like fracture network nucleus belt structure. Clearly recognizing the characteristics and internal structural differences of ultra-deep carbonate reservoir spaces is of great significance for the formulation of efficient oil and gas reservoir development plans in the Tarim Basin. It guides the deployment of wells and the optimization of well trajectories, leading to an increase in the success rate of high-yielding wells to over 96%, and provides new ideas for the next phase of efficient oil and gas exploration and development in the study area.

Key words: Tarim Basin, deep-tradeep, fractured and vuggy reservoirs, buried hill karst reservoirs, interlayer karst reservoirs, reservoir structure