Identification Method of Fractures and Vugs in Dolomite Reservoirs Based on Conventional Logging Curves

The dolomite reservoir of the Majiagou formation in the southeast of the Ordos Basin constitutes an important oil and gas reservoir. The development of fractures and vugs directly influences the reservoir's permeability and hydrocarbon storage capacity, making precise fracture-vug identification crucial for effective reservoir exploitation. Given the limitations of traditional fracture-vug recognition methods, the work adopted the R/S (Rescaled Range) analysis based on fractal theory and Newton's second-order difference method. The results are as follows. (1) The conventional logging curve was processed by R/S analysis. The concave interval reflected the developmental position of fractures and vugs. The greater the H , the more developed the fracture. Besides, corresponding identification standards were established. (2) Based on Newton's second-order difference, K was calculated. Rangeability was quantified in the concave interval of the curve to identify the natural fracture-vug development area. The accuracy and reliability of the method were verified by comparing the electro-imaging diagrams. (3) The differences and reasons for the response characteristics of K of different logging curves were analyzed to establish the identification plates of fractures and vugs development areas. This work provides a new method for the fracture-vug identification of Ordos Basin and other similar reservoirs, guiding the reservoir research and decision-making of oil and gas exploration and development.