Prediction and Visualization of Channel Characteristics for Lost Circulation of Drilling Fluid in Fractured Formations

Accurate characterization of the feature parameters of lost circulation channels in fractured formations is of great significance for assessing lost circulation risk and designing effective leakage prevention and plugging strategies. To address the limitations of existing fracture characterization methods in capturing both the spatial distribution and internal structural features of fractures, a case study was conducted in an oilfield in China. Considering the combined influence of fracture density and fracture aperture on fracture development, a fracture development index analytical model was established based on R / S fractal theory. Furthermore, a digital characterization method for complex lost circulation channels was developed using the Monte Carlo modeling technique. Based on logging interpretation results, the fracture development indices of four intervals in a selected well were calculated and compared with the corresponding borehole imaging logs. The results show that higher fracture development index values correspond to more developed fractures in the imaging logs, thereby confirming the reliability of the proposed index model. By integrating the actual distribution of fracture parameters in the study area with the fracture development index model, a digital representation of fractures with varying degrees of development can be achieved, providing a more realistic basis for numerical simulation of complex lost circulation scenarios. The dynamic lost circulation numerical model indicates that, as the fracture development index increases, the lost circulation channels tend to connect along the maximum horizontal stress direction. The research findings offer theoretical guidance for risk prediction of lost circulation and optimization of leakage prevention and plugging strategies.