关键词: 页岩气, 出砂, 临界出砂产量, 临界出砂流速, 压裂, 应力敏感

Abstract: The sand production of shale gas wells will reduce the flow conductivity of fractures, which in turn will reduce the production capacity of gas wells, and at the same time will cause sand plugging and erosion, thus affecting the safety of gas wells. Aiming at this problem, a prediction method for the critical sand production rate from shale gas wells was proposed. First, the critical flow rates of sand production of shale gas well fractures under different types of proppant were obtained, and the reasons leading to the difference in the critical flow rates of sand production of fractures were analyzed. Then, the critical sand production rates of shale gas wells under different fracture closure pressures was calculated in combination with the proppant mass and fracture half-length in gas well fractures. Finally, the method was validated using the field observation results of deep shale gas wells in the Longmaxi Formation of a certain block in west Chongqing. The results show that the stability of proppant and fracture varies at different stages of closure pressure, and the critical sand production flow rate is relatively low when the closure pressure is low and the equilibrium is broken due to the rupture of rock slab; the range of critical sand production flow rate of fracture corresponding to different proppant types also varies greatly, and the critical sand production flow rate of composite fracturing sand-propped fracture is relatively large in general, which is conducive to the prevention of sand production in gas wells. The sand production is predicted in 6 out of 15 wells within the example block, which is consistent with the actual production. The method is important for optimizing the early production allocation of shale gas wells.

Key words: shale gas, sand production, critical sand production rate, critical sand production flow rate, fracturing, stress sensitivity