PT Petrosea Tbk, the Indonesian subsidiary of Clough Limited Ð one of Australia’s largest multi-disciplinary engineering and construction groups Ð has signed a contract for a A$180-million (US$140-million), 48-month extension to its long-term coal overburden stripping contract in East Kalimantan.   The work for PT Gunungbayan Pratamacoal (GBP) was first awarded to Petrosea in November,…