Casing shoes and methods of reverse-circulation cementing of casing

A circulation valve for cementing casing in a well bore, the valve comprising:

• a valve housing connected to the casing;
• at least one hole in the valve housing, wherein the at least one hole allows fluid communication between an inner diameter of the valve housing and an exterior of the valve housing;
• a float plug positioned within the valve housing, wherein the float plug is moveable to a closed position on a ring seat within the valve housing;
• and
• a lock that locks the float plug in an open configuration allowing fluid to pass through the ring seat in the valve housing, wherein the lock comprises a chemically reactive material;
• wherein the chemically reactive material of said lock comprises a dissolvable material that dissolves by contact with an activator material, wherein the lock becomes unlocked upon dissolution of the dissolvable material.

A circulation valve for cementing casing in a well bore, the valve comprising:

• a valve housing connected to the casing;
• at least one hole in the valve housing, wherein the at least one hole allows fluid communication between an inner diameter of the valve housing and an exterior of the valve housing;
• a float plug positioned within the valve housing, wherein the float plug is moveable to a closed position on a ring seat within the valve housing;
• and
• a lock that locks the float plug in an open configuration allowing fluid to pass through the ring seat in the valve housing, wherein the lock comprises a chemically reactive material;
• further comprising a protective material that coats the chemically reactive material, wherein the protective material is erodable by an activator material to expose the chemically reactive material to a well bore fluid, whereby the lock becomes unlocked upon exposure of the chemically reactive material to the well bore fluid;
• wherein the chemically reactive material of said lock comprises a dissolvable material that dissolves by contact with a well bore fluid, wherein the lock becomes unlocked upon dissolution of the dissolvable material.