As you want address of Office of ONGC in Mumbai, so I am providing address here:

Mumbai High Asset
Rajesh Kakkar
Asset Manager
ONGC, Vasudhara Bhavan, Bandra (E), Mumbai – 400051
Telephone: 022-26599806 (Office), 022-26599808 (Fax)

Neelam & Heera Asset
A J Morbale
Asset Manager
ONGC, Vasudhara Bhavan, Bandra (E), Mumbai 400051
Telephone: 022-26599727 (Office), 022-26599760 (Fax)

Bassein & Satellite Asset
Sanjay Kumar Moitra
Asset Manager
ONGC, Vasudhara Bhavan, Bandra (E), Mumbai-400051
Telephone: 022-26599822 (Office), 022-26599833 (Fax)

Western Offshore Basin
G C Katiyar
Basin Manager
ONGC, Priyadarshini Building, Eastern Express Highway, Sion, Mumbai-400022
Telephone: 022-24045249 (Office), 022-24045398 (Fax)

ONGC Office in Navi Mumbai
Institute of Oil & Gas Production Technology (IOGPT)
C P Singhal
Head IOGPT
ONGC Complex, Phase-II, Panvel, Navi Mumbai – 410221
Telephone: 022-27486000
/6997/6998 (Office), 022-27451690 (Fax)

Institute of Engineering & Ocean Technology (IEOT)
C Tandi
Head IEOT
ONGC Complex, Phase-II, Panvel, Navi Mumbai – 410221
Telephone: 022-27451893 (Office), 022-27486350 (Fax)