The Pike River recovery team expects to break the main seal and push further into the mine by Christmas if all goes according to plan.
WorkSafe has signed off on an exemption that will allow the next phase of the manned re-entry.
That involves breaking the seal at 170 metres and a team assessing and collecting forensic evidence along the mine tunnel to a large rockfall at the 2.3 kilometre mark - the end goal for the operation.
Twenty-nine men died in the 2010 explosion and many families have been campaigning to re-enter the mine ever since.
Dinghy Pattinson, the chief operating officer for the Pike River Recovery Agency, explains what happens next.