Annular casing packers are run in the well as a component of the casing. They are permanently set to seal the annular gap created with the previous casing string. Annular casing packers help prevent upward or downward movement of fluids or pressures during and after cementing operations. When run in conjunction with a multiple-stage cementing tool, the packer can support the hydrostatic pressure created by the column of cement displaced into the annulus above the packer or prevent gas migration from below the packer into the displaced second-stage cement.
Obex™ Annular Casing Packer
The Obex™ annular casing packer is designed to be set inside cased holes to provide a high-pressure, gas-tight, casing-to-casing seal. This seal helps mitigate annular gas migration and/or supports the hydrostatic weight of annular well fluids above the Obex annular casing packer in wells with weak formation zones.
For more specifications:
http://www.halliburton.com/en-US/ps/cementing/casing-equipment/casing-packer/annular-casing-packer.page?node-id=hfqela4y
