Expandable casings strings applied by Tatneft on a commercial scale allowed complete exclusion of intermediate casing strings from the well designs in the Volga-Ural oil-producing region. Underway is research and pilot tests of expandable systems to isolate trouble zones as thick as 500-1000 m. For expanding of casing strings mechanical and hyd - raulic expansion mandrels are used, along with hydraulic jack, anchor, and by-pass valves.
