Figure F4. Photographs of subseafloor borehole observatory (CORK) seal systems and components used during Expedition 327. A. Casing seal subs attached to 10¾ inch casing hangers. Sealing is accomplished with a combination of metal-on-metal and O-ring contact between the 10¾ and 16 inch casing hangers. B. Swellable casing packer installed near the top of the 10¾ inch casing strings in Holes U1362A and U1362B. The rubber element is composed of a material that reacts and expands in the presence of seawater, helping to fill the annular gap between the packer element and the 16 inch casing. C. CORK seal at the base of the Hole U1362A wellhead. The seal is formed by two polypacks, U-shaped plastic pieces that surround an O-ring. Note sampling and monitoring tubes that pass through the CORK seal, connecting wellhead instruments and valves above to the formation intervals at depth. D. Inflatable packer element with 8½ inch outside diameter, installed at depth inside casing and open hole. Inflatable packers were deployed in tandem with swellable packer elements, helping to isolate open basement intervals. E. Swellable casing packer installed on 4½ inch CORK casing. Tubing umbilicals pass through the packer using slots premilled into the element housing. This particular element was turned down on a lathe to make the diameter small enough to permit deployment in the open hole. These swellable casing packers are deployed in pairs. F. Lower end of top plug for Hole U1362A CORK. The top plug is sealed by an O-ring held in position against a tapered seal area by the weight of the plug, instrument string, and sinker bar.
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