Twinza has been involved in negotiations with the PNG Government over its Pasca A project, the first offshore development situated in the Gulf Province.
Twinza said Mr Munro had elected not to renew his employment contract as chief executive beyond its expiry on 30 September.
Mr Quantrill has also been appointed chairman of the board, replacing Mr Munro, while a CEO search process is underway.
In recent Twinza statements, Mr Munro expressed his disappointment and concern about the way in which negotiations on Pasca project have progressed.
