US Patent 11459852 Actuating a frangible flapper reservoir isolation valve

A method for wellbore fluid flow control in which a frangible flapper is disposed in a wellbore. The frangible flapper is engaged to a flow tube disposed within the wellbore to keep the frangible flapper in a biased open position to allow fluid flow through the wellbore. The method includes moving the flow tube longitudinally in a first direction within the wellbore and relative to the frangible flapper. The method includes responsive to moving the flow tube longitudinally in the first direction, disengaging the flow tube from the frangible flapper. The method includes responsive to disengaging the flow tube from the frangible flapper, causing the frangible flapper to move from the biased open position to an unbiased shut position. The method includes responsive to the frangible flapper moving to the unbiased shut position, stopping fluid flow within the wellbore from a downhole location downhole of the frangible flapper.