A system and method for use in a wellbore that includes a string comprising a housing. The housing comprises a valve including a valve seat having an inner channel and a flapper configured to pivot relative to the valve seat between a first position and a second position in which the inner channel is...http://www.google.com/patents/US7779919?utm_source=gb-gplus-sharePatent US7779919 - Flapper valve retention method and system
