A technique for abandonment of a hydrocarbon well injects cement into the annulus through apertures (5) in the casing (3). The apertures (5) are pre-formed in the casing before the casing is installed at the start of life of the well, and are also fitted with a closure sleeve (6). The apertures (5) remain closed for the lifetime of the well. The closure sleeve (6) is designed to remain operational over the 20-30 year lifetime of the well. When the time comes to plug and abandon the well, a tool (9) is passed down the well on drill pipe (10) to open the apertures (5) by moving the sleeve (6). Wash fluid and then cement are injected from the tool (9) through the apertures (5) to wash and then plug the annulus behind the casing (3).