An Overview of the Differential Carbonate Reservoir Characteristic and Exploitation Challenge in the Tarim Basin (NW China)

The largest marine carbonate oilfield and gas condensate field in China have been found the Ordovician limestones central Tarim Basin. They are defined as large “layered” reef-shoal karstic reservoirs. However, low and/or unstable oil/gas production has a big challenge for effective exploitation ultra-deep (>6000 m) reservoirs more than 20 years. Together with static dynamic reservoir data, we review of unconventional characteristics fields that: (1) area tight matrix (porosity less 5%, permeability 0.2 mD) superimposed localized fracture-cave > 2 mD); (2) complicated fluid distribution without uniform oil/gas/water interface an field; (3) about 30% wells fractured support 80% production; (4) high decline rate is over 20% per year recovery ratio. These data suggest that “sweet spot” rather major drilling target development. In pre-Mesozoic reservoirs, further advances horizontal multiple fracturing techniques needed economic seismic quantitative descriptions across fault zones efficient development from deeply