Reverse circulation cementing system for cementing a liner

A method of cementing a liner in a wellbore extending through a subterranean zone using reverse circulation, the method comprising the steps of:

• a. running a tubing string into the wellbore so that a wellbore annulus is defined therebetween, the tubing string defining an interior passageway along its length and having a reverse circulation assembly, a liner hanger, and a liner positioned below the liner hanger;
• b. circulating fluid along a conventional circulation path during step a) by flowing fluid downhole through the interior passageway and uphole through the wellbore annulus;
• c. sealing the wellbore annulus uphole from the liner by setting an annular isolation device in the wellbore annulus;
• and
• d. flowing cement along a reverse circulation path downhole from the annular isolation device by opening a reverse circulation port of the reverse circulation assembly to permit fluid flow from the interior passageway to the wellbore annulus at a position between the annular isolation device and the liner hanger.