Cyclic check valve for coiled tubing

The invention relates to coiled tubing strings, and in particular to at least partial dual tubing strings, including methods for assembling such strings. More particularly, the invention relates to a cyclic check valve for use in coiled tubing strings. A cyclic check valve 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 which may be de-activated by shiftable sleeve locked in place by a J-slot assembly. The check valve may be cycled from the activated to de-activated position and verified by a change in pressure drop through the tool.