The effect of gravel packing in screen casing annular and perforations on the well productivity can be shown by gravel pack productivity ratio, which can be calculated by the additional skin factor.

• 计算射孔孔眼砾石层及环空砾石层的附加表皮因数 ,用砾石充填后产能比考虑炮眼和筛套环空砾石充填对产能的影响 ;压裂增产倍数与砾石充填产能比的乘积即为压裂充填防砂后的总产能比。