Experimental and Numerical Investigation of Multiscale Fracture Deformation in Fractured–Vuggy Carbonate Reservoirs

Fractures intersected with borehole are extremely sensitive to borehole pressure fluctuations, which causes the fractures to evolve into loss channels during well operations. This paper presents fracture deformation and pressure distribution within a single fracture, by combining experimental study of micro-fractures with numerical analysis of macro-fractures based on ANSYS software. Additionally, the deformable behavior of fracture considering the fluid–solid coupling effect is investigated, and the pressure distribution within the fracture during mud loss process is numerically simulated. It is revealed that fracture mouth expanded to the biggest as borehole fluid pressure transfers from fracture mouth to fracture tip, which results in lost circulation frequently due to the solid particles of drilling fluid failing to plug rapidly and effectively the opened fracture. To avoid lost circulation incidents, the acid-soluble lost circulation materials should be added according to the fracture deformation behavior before drilling the reservoirs with strong stress sensitivity.