关键词: 垂直井;断层突水;起裂压力;延伸压力;压裂缝延伸模型

Abstract: Aiming at geological problems such as water inrush in fractured reservoirs triggered by hydraulic fractures. Firstly， according to the principle of elastic mechanics and fracture mechanics strength criterion， based on the geometric characteristics of reservoir primary fracture and the seepage law of fracturing fluid， the calculation model of fracture initiation pressure under vertical well condition is established. Secondly， considering the damage constitutive relationship of coal reservoir， the Dougill damage factor is combined with the fracture initiation pressure formula to further establish the extension pressure calculation model. Using the classic PKN model and the nonlinear pressure drop law of the net pressure in the fracture， an improved fracture propagation model is established. The model reveals the non-linear relationship between fracture length L and fracturing time t in fractured reservoirs， showing that the extension distance of fractures increases with time， but it increases rapidly in the early stage and basically stabilizes in the later stage. The calculation results of three test wells in the Encun block of Jiaozuo in northern Henan Province are in good agreement with the microseismic data of the adjacent block， which verifies the correctness of the theoretical model and provides reliable technical support for on-site fracturing parameter control and prevention of fracture water inrush.

Key words: vertical well; fault inrush; fractured pressure; extension pressure; fracture extension model