Geological factors of well fracability in Fuling shale gas field, Sichuan Basin

Brittle mineral content, brittle index and horizontal stress difference coefficient of shale reservoirs are the main factors influencing shale fracability. The ①-⑤ layers from the Wufeng Formation to the first member of Longmaxi Formation in the Fuling shale gas field have similar brittle mineral content (>50%), brittle index (>50%), and horizontal stress difference coefficient (<0.2). Therefore, the above parameters can not be used effectively to evaluate the fracability of a single well in this block. Based on a large amount of single well data, the authors assessed the influence of various geological factors on the fracability of a single well by geological factors such as burial depth, structural form and fracture development characteristics. The results showed that:(1) Burial depth is the most important geological factor affecting single well fracability, and the greater the burial depth, the greater the difficulty of reservoir fracturing; (2) Structural morphology has a more obvious effect on fracturing, and fracturing is more difficult in negative structures than in positive ones; (3) The heterogeneity of natural fractures will also lead to the increased difficulty of fracturing, the difficulty of extending seam networks, affecting the effect of reservoir reconstruction and reducing the productivity of a single well.