US Patent 10100601 Downhole assembly having isolation tool and method

A downhole assembly includes an isolation tool disposable downhole of a perforation gun. The isolation tool includes a tubular body having a seat, and an occluding device supported on the tubular body in an unseated position, and movable to a seated position on the seat in response to at least one of a firing operation of the perforation gun and a selected fluid velocity through the isolation tool. Fluid communication through the isolation tool is allowed in uphole and downhole directions in the unseated position of the occluding device, and blocked in the downhole direction in the seated position of the occluding device.