Behind casing wash and cement

A method of performing a downhole wash procedure in an offshore well in a region of casing having perforations or other openings, the method comprising:

• passing a washing tool down the casing to the region with perforations or openings, the washing tool having a plurality of nozzles and being connected to a supply of wash fluid;
• delivering wash fluid through the nozzles whilst rotating the washing tool and translating the washing tool in an axial direction with respect to the casing, such that wash fluid is forced through the perforations and pulses of pressure are created in an annulus between the casing and the rock formation of the wellbore;
• wherein:
• whilst delivering wash fluid, the translational movement of the washing tool is in a downward (distal) direction only.