Choking orifice collar for casing floatation operations

A method for using a casing string floatation system, the method comprises:

• introducing the casing string floatation system into a wellbore;
• the casing string floatation system comprising:
• a casing string comprising:
• a plurality of casing joints coupled together,
• a casing shoe disposed at a bottom of the casing string, and
• a floatation subassembly comprising a buoyant chamber and disposed uphole of the casing shoe,
• a removable plug disposed in the casing string and defining an uphole end of the floatation subassembly,
• a choking orifice collar disposed in a casing joint of the plurality of casing joints;
• wherein the choking orifice collar comprises an orifice having a diameter smaller than an inner diameter of the casing joint in which the choking orifice is disposed;
• wherein the choking orifice collar is structurally and locationally distinct from the floatation subassembly, and
• a casing tool disposed within or on the casing string and disposed uphole or downhole of the floatation subassembly, wherein the casing tool is configured to actuate from an application of pressure to the casing tool;
• removing the removable plug,
• flowing a fluid into the floatation subassembly, and
• choking the flow of the fluid with the choking orifice collar such that a rate of the fluid flow into the floatation subassembly is reduced.