Apparatus for stage-cementing an oil well

An apparatus for use in stage-cementing a fluid production well in a region of a lost circulation zone that is proximate an annular space defined between a lower end of an outer casing surrounding an inner casing, the inner casing being formed by a cylindrical sidewall having an outer surface, the outer casing being formed by a cylindrical sidewall having an inner surface that has an inside diameter that is greater than the outside diameter of the inner casing, the apparatus comprising:

• a load-bearing annular steel plate having an outside diameter and an inside diameter, the outside diameter of the load-bearing annular steel plate being greater than the inside diameter of the load-bearing annular steel plate to form a ring-shaped plate, the inside diameter of the annular steel plate forming a central opening that is greater than the outside diameter of the inner casing, the annular steel plate being immovably positioned on a section of the inner casing relative to a longitudinal axis of the inner casing, the annular steel plate having an upper surface and a lower surface, the upper surface having a continuous annular raised shoulder positioned to continuously surround the central opening, and wherein the outside diameter of the annular steel plate is less than the inside diameter of the outer casing;
• and
• an inner casing coupling for joining a pair of adjacent longitudinally aligned casing sections of said inner casing, the inner casing coupling having an outside diameter greater than the outside diameter of the inner casing, the inner casing coupling having an upper surface that is positioned below and supports the lower surface of the annular steel plate.