Zone Isolation Block
Optimal distribution of steam can significantly improve the recovery factor of a heavy oil or bitumen reservoir. Thermal recovery utilizing steam, has been extensively and successfully used in many heavy oil wells.
Although Steam injection has enhanced oil recovery, history has also shown us that steam injection has created challenges. Some of these challenges result in having steam break though on SAGD wells, or unwanted water production through lower zones in horizontal wells, or thermal expansion causing failure to seals and hangers. These problems can result in costly work-overs associated with down hole equipment failures, reduced recovery, or loss of the well.
A specifically designed and engineered Zone Isolation Cylinders (ZIC) are placed within the production liner at specific depths or positions within the well. The production liner may be slotted or sand screen liner that is hung within the well, or installed on production liner that is cemented, and perforated. In either case, the ZIC are installed in areas that will separate sections of the well. This separation may be required to isolate different production zones, due to product or pressure differences. This separation may be required to distribute steam better throughout the well. This separation may be required to shut off certain sections of the well, due to water or steam break through.
The completion string, used for injection of steam or other fluids, and retrieving the produced fluids, will be installed within the production string containing the ZIBs. The Zone Isolation Blocks (ZIB) are installed within this completion string, and will coordinate with the positions of the ZIC within the production liner. Each ZIC installed within the production liner will decrease in inside diameter (id) as the depth of the liner increases. Coincidently, the ZIB will also decrease in outside diameter (od) by the same amount as its mating ZIC. When the completion string’s ZIBs line up with the production liner’s ZICs, the Blocks will slide inside their mating Cylinders to complete a seal. There are different types of Block designs. Some may contain elastomeric seals for high pressure sealing. Others are designed to incorporate instrumentation lines such as Fiber Optic Lines. All Blocks will contain steel seal systems, and are all allowed to move due to thermal expansion, and still obtain a seal through movements and pressures. Both the ZIB and the ZIC are manufactured from hardened steel material, will not wash or fail under high steam temperatures and pressures during pipe movements. Depending on the Block design, most ZIBs will have a positive-seal-memory when set inside the ZICs. There is no need for hydraulic or mechanical movement to set or inflate seals on the ZIB. Only string weight is required to set the steel seals of the ZIB within its matched ZICs. The ZIC and ZIB work in combination with the Staging Diverter Pup (SDP) to inject, produce, or isolate specific sections of the well.