potential energy equal to and opposite in direction to the stretching compressing force is stored in the material as in a spring such that when the stretching compressing force is removed the material can return to its original configuration it is this stored energy that is commonly referred to as 34 pre load 34 the metal annulus valve element 22 of the annulus closure system comprises a central annular body 22a inner and outer annular sealing lips 22b 22c respectively that extend downward from the body portion 22a and an annular rib 22d that faces inwardly from the upper end area of the body 22a as seen best in fig5 and 6 each of the sealing lips 22b 22c has an annular sealing surface 22e 22f respectively with a radiused configuration that assures a pressure tight metal to metal seal with adjacent annular sealing surfaces 24a 24b of the chamber 24 when the valve element is in its closed position shown in fig3 and 8 the lower portion of each chamber sealing surface 24a 24b is chamfered to facilitate movement of the lip sealing surfaces 22e 22f onto the chamber sealing surfaces as the valve element 22 is lifted into its closed position and when in that position the lip sealing surfaces are in an interference fit relationship with the opposing chamber sealing surfaces the annulus valve element 22 is moved between its open and closed positions by a well tool such as the annulus valve operating sleeve 52 illustrated in fig2 as best seen in fig3 8 the sleeve 52 includes a tubular mandrel 54.