Method and device for facilitating the insertion of a coiled tube into a well and for loosening stuck objects in a well

Abstract

Method for overcoming friction between a coiled tube and the wall of a well by an oil- or gas well, and for enabling application of impact energy to loosen stuck objects in a well. Pressure changes are applied to a liquid flowing in the coiled tube by periodically shutting off the liquid flow at or near the outlet of the coiled tube. Pressure changes, pressure strokes, are applied by means of a valve device comprising a valve body (,) arranged to seal against a valve seat (,) and to shut off the liquid flow whenever the flow rate exceeds a predetermined value, and to remain shut until the pressure in the liquid upstream of the valve body (,) is lower than a predetermined value, and that the valve body (,) has a slide (,) arranged thereto, which is arranged to open for a liquid flow past the valve body (,), to reduce, thereby, the pressure in the liquid upstream of the valve body (,) whenever the pressure in the liquid upstream of the valve body (,) exceeds a predetermined value. A damping device in which pistons in the form of collars (,), channels (,) and check valves (,) are moved in annular spaces (,) filled with liquid, contributes to the valve device being closed long enough for a pressure rise to spread in the liquid in the coiled tube, and being open long enough for full liquid flow to be established before the next shut-off.