Optimization of Staged Fracturing and Cluster Design for Horizontal Wells in Low-Permeability Reservoirs Based on Mechanical Specific Energy

The fracturing design of horizontal wells in low-permeability reservoirs mostly relies on static data such as logging data, and insufficient utilization of while-drilling information from drilling and mud logging leads to an unreliable basis for staged fracturing and cluster design, making it difficult to achieve efficient reservoir stimulation. To address this issue, this paper takes mechanical specific energy (MSE) as the core engineering parameter. Based on the drilling and mud logging data from the horizontal section of an example well, a mechanical specific energy model is established after data preprocessing. The K-medoids unsupervised clustering algorithm is adopted to realize the fine division of fracturing stages, and the optimal number of stages is determined using the elbow method. A fracturing sweet spot index (FSI) is constructed using the random forest algorithm. This index integrates four key parameters: oil saturation, porosity, permeability, and mechanical specific energy to optimize perforation cluster placement. The proposed method is validated through finite element numerical simulation and field data comparison. The research results show that the optimal division of the example well is determined as 11 stages with six clusters per stage, and the matching degree between stage-cluster division and reservoir heterogeneity is significantly improved. Compared with the original scheme, the stimulated reservoir volume (SRV) of the optimized construction scheme is increased by 19.6%, and the treatment pressure exhibits an obvious overall reduction trend, as demonstrated by the construction pressure curves. The research indicates that this method can make full use of drilling while-drilling data to realize integrated geological and engineering evaluations of fracturing and optimization of staged fracturing and cluster designs, and can provide effective technical support for the fracturing optimization design of horizontal wells in low-permeability reservoirs lacking complete logging data.