100 to an actuation pressure sufficient to substantially simultaneously or sequentially burst rupture disks 150 256 for example when the actuation pressure of rupture disks 256 is reached and rupture disks 256 burst fluid pressure from the wellbore enters activation chamber 252 via fluid passageway 254 the force generated by the fluid pressure acting on a lower surface of lower piston 236 breaks the shear screws 262 allowing lower piston 236 to move upwardly against any opposing force generated by pressure within atmospheric chamber 270 which is preferably negligible lower piston 236 moves together with body lock assembly 232 to apply a compressive force against seal assembly 224 when the compressive force reaches a predetermined level shear screws 218 break allowing release sleeve 214 to shift upwardly relative to packer mandrel 104 the upwardly moving release sleeve 214 contacts collet assembly 216 causing radial retraction of the collet fingers of collet assembly 216 decoupling collet assembly 216 from lower intermediate piston 208 as best seen in fig3 d preferably at the same time when the actuation pressure of rupture disks 150 is reached and rupture disks 150 burst fluid pressure from the wellbore enters activation chamber 146 via fluid passageway 148 the force generated by the fluid pressure acting on an upper surface of upper piston 156 breaks the shear screws 162 allowing upper piston 156 to move downwardly against any opposing force generated by pressure within atmospheric chamber 264 which is preferably negligible upper piston 156 moves together with body lock assembly 164 to apply a compressive force against seal assembly 168 when the compressive.