Cyclic check valve for coiled tubing

A cyclic check valve SV is provided for a coiled tubing string which enables reverse circulating for a specific period when a specific combination of pumping condition and oil conditions are favorable. The check valve may be activated to prevent reverse flow up through the valve and into the coiled tubing in the event of a failure of the coiled tubing at surface. The valve may be de-activated to allow reverse circulating. The check valve includes a flapper valve F which may be de-activated by shiftable sleeve locked in place by a J-slot assembly Fig 8. The check valve may be cycled from the activated to de-activated position and verified by a change in pressure drop through the tool. The coiled tube may have an inner tubing IT Fig 3, along at least some of it's length. There is little annular gap between the inner and outer tubes. There is sealing between the tubes at the ends of the inner tube. Various sealing constructions are disclosed.