BURIAL KARST CHARACTERISTICS OF ORDOVICIAN CARBONATE RESERVOIRS IN CENTRAL TARIM BASIN

Various types of karstification effects have developed in the Ordovician carbonate reservoirs of the central Tarim Basin.The deep burial and hydrothermal Karstification effects play important roles in favorable reservoir formation.Analyses of well cores,logging data and geological background have indicated that,there are mainly 4 stages of burial Karstification effects in the area.The pores in stages Ⅰ and Ⅱ have been filled.The residual pores in stage Ⅲ and the corrosion pores in stage Ⅳ work as effective reservoir space for present reservoirs.The main fluid medium include organic acid and CO₂ generated during organic evolution.H₂S may contribute to late reservoir formation.Hydrothermal Karstification is effective to Ordovician reservoir transformation.The influence and evaluation still require further research.