Shashi Shanker has been appointed Chairman and Managing Director of India's biggest oil and gas producer, ONGC, till March 2021.The Appointments Committee of the Cabinet (ACC) named Shanker, who is currently Director (Technical and Field Services) at ONGC, as CMD till his superannuation. Mr Shanker, 56, will take charge from October 1st when the incumbent Dinesh K Sarraf retires and will have a three-and-a-half-year term until March 31, 2021.