Patent ID: 6571880
Filing Date: 2003-06-03
Classification: E21B

Abstract:
A method for cementing a casing string into an earth borehole, said casing string having an upper portion and a lower portion, said method comprising:securing an upper mandrel to a lower mandrel utilizing a sleeve detachably mounted to said upper mandrel while being maintained within said lower mandrel, said sleeve having a sealable seat at its upper end; positioning said upper mandrel and said lower mandrel within said earth borehole; dropping a first ball of a given diameter into said earth borehole, and allowing said first ball to come to rest against said sealable seat of said sleeve; increasing at the earth's surface, to a first pressure level, the pump pressure pumped against said first ball to shear at least one first shear pin detachably mounting said sleeve within said upper mandrel until said first pressure is applied, thereby causing said lower mandrel maintaining said sleeve to separate from said upper mandrel; pumping said lower mandrel downwardly through a plurality of tubulars comprising said casing string as a selected volume of cement is pumped into said earth borehole; increasing at the earth's surface, to a second pressure higher than said first pressure level, the pump pressure against said first ball to shear at least one second shear pin within said lower mandrel to move said sleeve downwardly within said lower mandrel, thereby allowing said cement to be pumped through said lower mandrel and through said lower portion of said casing string and into an annulus between said casing string and said earth borehole to thereby cement said casing string within said earth borehole.