Abstract: A cementing tool (20) capable of being installed in a casing string (10) and configured to selectively permit the flow of cement through one or more ports (34) in the tool is provided. The ports (34) are normally sealed by rupture disc assemblies (36) comprising a rupture disc (62) that can be opened to permit flow of cement through the casing string central bore (32) and into the annulus (14) defined by the casing string (10) and the downhole formation (16). The cementing tool (20) is particularly useful during cementing operations in which the annulus (14) has become blocked by a collapsed portion of the formation by allowing the obstruction (104) to be bypassed and the flow of cement (100) into the annulus to be continued without substantial interruption. Tool (20) may also be used in multistage cementing operations.

Abstract: A cementing tool (20) capable of being installed in a casing string (10) and configured to selectively permit the flow of cement through one or more ports (34) in the tool is provided. The ports (34) are normally sealed by rupture disc assemblies (36) comprising a rupture disc (62) that can be opened to permit flow of cement through the casing string central bore (32) and into the annulus (14) defined by the casing string (10) and the downhole formation (16). The cementing tool (20) is particularly useful during cementing operations in which the annulus (14) has become blocked by a collapsed portion of the formation by allowing the obstruction (104) to be bypassed and the flow of cement (100) into the annulus to be continued without substantial interruption. Tool (20) may also be used in multistage cementing operations.