The reasons for sand production include the decline of formation pressure, the clasticdeformation of rock matrix, the breakdown of sand cementing matter and the washout ofhigh speed fluid.

• 出砂的原因是：油层孔隙压力降低，砂岩骨架被压碎；孔隙内介质变化使胶结物破坏；高流速下液体冲坏砂拱等。