Cementing tool and method for cementing a casing assembly at a junction

A tool 110 for cementing a casing junction assembly 100 at a well junction 21 comprises: a body 111; a releasable anchoring mechanism 114; and a flow conduit 113, and preferably also sealing elements 116 between the body 111 and the junction assembly 100; a flow control device 119; bypass conduits 120; and a barrier (126, figure 7)to prevent cement backfilling the internal volume 100a of the junction assembly 100. A method is also claimed, comprising the steps of lowering the above tool 110 into the junction assembly 100 so that the anchoring mechanism 114 engages; pumping cement slurry through the cementing tool 110 to fill the annular region outside the junction assembly 100; disengaging the cementing tool 110 from the junction assembly 100; and removing the cementing tool 110 from the junction assembly 100. Another method claimed comprises the steps of pumping cement down a work string 112; channelling cement flow from the work string 112 through at least one bypass device 120 extending through the internal volume 100a of the junction assembly 100 and down a lateral branch 100b of the junction assembly 100 into the fluid channel 109 in the guide show 108; and preventing the flow of cement exiting the guide shoe 108 from back filling into the internal volume 100a of the junction assembly 100.