An annular seal for a setting tool in a packer tieback extension comprises a downhole oriented packer cup assembly. As the tool is run in the hole the packer cup flexes as the rising hydrostatic pressure equalizes across the cup into what started as a zone with atmospheric pressure inside the packer tieback extension. Once the pressure is equalized the self energizing feature of the packer cup maintains grit and debris in the mud from entering the tieback extension where the spring loaded dogs of the setting tool are held in a retracted position. If the seal fails to equalize and allows a large differential across the setting sleeve from the surrounding annulus, the rupture disc breaks inwardly into the tieback extension so that pressure is equalized. If the packer is never set after being lowered to depth and the pressure from the tieback extension is equalized into the annulus.