Method for replacing filling layer without changing pipe string, flowback service device and well completion structure

The invention relates to a method for replacing a down-hole packer particle filling layer without changing the down-hole pipe string flowback. The filling layer filled with packer particles are arranged in an annulus between a down-hole pipe string and the borehole wall, and a sliding sleeve type filling tool is arranged at the heel end of the down-hole pipe string. The method includes the following steps that a sliding sleeve of the sliding sleeve type filling tool is opened, and a flowback channel is established; and flowback fluid is injected into the down-hole pipe string through a feedingpipe string, the flowback fluid enters the annulus through a flow control device of the down-hole pipe string, the packer particles carried in the annulus are discharged from a wellhead through a filling hole and an oil jacket annulus, and after the flowback, the packer particles are then filled. According to the method, traditional down-hole packer and flow control screen pipe string salvage operation is avoided, the bl