A Logging Identification Method for Fractured Vuggy Carbonate Reservoirs Based on Curve Reconstruction: A Case Study from the Pz Formation in Karabulak Oil Field in the South Turgai Basin*

The basement carbonate reservoirs in the Karabulak oil field of the South Turgai Basin have the characteristics of complex structure, variety of pore type and strong heterogeneity. The identification of such reservoirs by single conventional logging method is always a difficult point in logging interpretation. In this paper, the response characteristics of conventional logging curves such as deep lateral resistivity, acoustic time difference, density and compensated neutron were used for reconstruction. Combined with the improved method of curve change rate, the response laws of fractured carbonate reservoirs, pore-cave reservoirs and fractured vuggy reservoirs on conventional logging curves were summed up, respectively. And a new logging evaluation method for carbonate fractured vuggy reservoirs in the Karabulak oil field of South Turgai Basin was proposed. This method was used to identify reservoirs in X1, X2 and X3 wells of this oilfield. The results show that the carbonate reservoirs in this area are mainly fractured-vuggy type. Compared with the oil test conclusion and imaging logging, the method proposed in this paper accurately divided the reservoir type. And the efficiency and accuracy of the reservoir division have been greatly improved.