A wellbore completion, comprising: a casing assembly comprising a plurality of casing lengths (106a, 106b, 106c, 206a, 206b, 206c) and at least one collar (110, 210), wherein the at least one collar (110, 210) comprises, a tubular body having an inner flow path; at least one fracture port (112, 212A, 212B) configured to provide fluid communication between an outer surface of the at least one collar (110, 210) and the inner flow path; at least one valve hole within the at least one collar (110, 210) intersecting the at least one fracture port (112, 212A, 212B); at least one valve vent hole (114, 214) positioned to provide fluid communication between the valve hole and the inner flow path; and at least one valve (120, 220) positioned in the valve hole for opening and closing the at least one fracture port (112, 212A, 212B), characterized in that, the at least one collar (110, 210) is positioned so as to couple the casing lengths (106a, 106b, 106c, 206a, 206b, 206c) and the valve (120, 220) being configured to open when a pressure differential is created between the at least one fracture port (112, 212A, 212B) and the at least one valve vent hole (114, 214). a casing assembly comprising a plurality of casing lengths (106a, 106b, 106c, 206a, 206b, 206c) and at least one collar (110, 210), wherein the at least one collar (110, 210) comprises, a tubular body having an inner flow path; at least one fracture port (112, 212A, 212B) configured to provide fluid communication between an outer surface of the at least one collar (110, 210) and the inner flow path; at least one valve hole within the at least one collar (110, 210) intersecting the at least one fracture port (112, 212A, 212B); at least one valve vent hole (114, 214) positioned to provide fluid communication between the valve hole and the inner flow path; and at least one valve (120, 220) positioned in the valve hole for opening and closing the at least one fracture port (112, 212A, 212B), characterized in that, the at least one collar (110, 210) is positioned so as to couple the casing lengths (106a, 106b, 106c, 206a, 206b, 206c) and the valve (120, 220) being configured to open when a pressure differential is created between the at least one fracture port (112, 212A, 212B) and the at least one valve vent hole (114, 214). a tubular body having an inner flow path; at least one fracture port (112, 212A, 212B) configured to provide fluid communication between an outer surface of the at least one collar (110, 210) and the inner flow path; at least one valve hole within the at least one collar (110, 210) intersecting the at least one fracture port (112, 212A, 212B); at least one valve vent hole (114, 214) positioned to provide fluid communication between the valve hole and the inner flow path; and at least one valve (120, 220) positioned in the valve hole for opening and closing the at least one fracture port (112, 212A, 212B), characterized in that, the at least one collar (110, 210) is positioned so as to couple the casing lengths (106a, 106b, 106c, 206a, 206b, 206c) and the valve (120, 220) being configured to open when a pressure differential is created between the at least one fracture port (112, 212A, 212B) and the at least one valve vent hole (114, 214).