Patent ID: 8657018

Claim:
A circulating sub apparatus comprising: a substantially tubular outer body member having a throughbore formed therein; a substantially tubular inner body member; wherein at least the outer body member further comprises at least one hole formed therein; and a displacement mechanism for producing movement of the inner body member relative to the outer body member such that the inner body member is moveable between: an open configuration, in which the hole(s) on the outer body member are open such that fluid is passable between the throughbore and the outside of the circulating sub apparatus via the one or more holes; and, an obturated configuration, in which the hole(s) on the outer body member are obturated; wherein the inner body member comprises a seat member adapted to catch a dropped object, the seat member located upstream of the hole(s) of the outer body member in both the open and obturated configurations, and wherein the seat member is adapted to permit at least a proportion of fluid to flow past the dropped object when it is seated thereon.