As you want Compare Oil and Natural Gas Corporation (ONGC) with Oil India Ltd, so on your demand here I am telling short info of both companies :

Oil and Natural Gas Corporation Limited (ONGC) is an Indian multinational oil and gas company headquartered in Dehradun, Uttarakhand, India.

Company profile
Type Public Sector Undertaking
Traded as NSE: ONGC
BSE: 500312
BSE SENSEX Constituent
CNX Nifty Constituent
Industry Oil and Gas
Founded 14 August 1956
Headquarters Tel Bhavan,Krishna Nagar, Dehradun, Uttarakhand, India
Key people Shashi Shanker
(Chairman & MD)
Products Petroleum, natural gas, and other petrochemicals
Revenue 3,245,670.35 crore (US$510 billion) (2017)
Profit 1,577,502.00 crore (US$250 billion) (2016)
Total equity 5,167,321.76 crore (US$810 billion)
Owner Government of India (68.9438%)
Number of employees 7.3 million + (2017)
Divisions
MRPL
ONGC Videsh Ltd.
HPCL Ltd.

Oil India Limited (OIL) is the second largest hydrocarbon exploration and production Indian public sector company with its operational headquarters in Duliajan, Assam,hold approx 9000 plus employee, India under the administrative control of the Ministry of Petroleum and Natural Gas.

Company profile :
Type Public Sector Undertaking
Industry Oil and gas
Founded 18 February 1959
Headquarters Duliajan, Assam, India
Key people Mr Utpal. Bora
(Chairman & MD)
Products Petroleum, natural gas, and other petrochemicals
Owner Government of India (66%)