Slimhole DST String
Reservoir testing in slim holes
Enable downhole reservoir testing in small-casing wells down to 4 1/2-in casing.
The multicycle circulating valve with lock is a reclosable valve operated by tubing pressure and is used for spotting fluids and nitrogen. The valve responds to changes of flow direction rather than rate changes, making it insensitive to rate while circulating or reversing and enabling spotting nitrogen cushions and nitrified acids. It is also unaffected by the operation of annular-pressure-operated tools and is not limited in operation by available surface pump horsepower.
The lock module retains the mandrel in the open or closed position. When the lock is engaged, internal pressure testing can be conducted without using up cycles. The valve is also insensitive to pressure surges in the tubing or annulus, which is advantageous when locked in the open (reverse) position to automatically fill the string while running in hole.
To unlock the tool, applied annulus pressure is used to rupture a preset disc, which disengages the lock. The valve can be cycled to reverse or circulate position and then reclosed.