Annular Space Volume = volume of hole - volum of casing, where:
Volume of hole = 3.14 x (Diameter of Hole/2)² x Depth
and
volume of caing = 3.14 x (outer diamerof of casing/2)² x depth:
Diameter of hole is 10"
Depth 20 ft
diameter of casing 6-5/8"
