Organizational Structure of ONGC
Basin – Any area where ONGC is trying to find/ explore oil, can be on-land called Onshore or beneath a sea called Offshore.
ONGC’s primary aim is to produce crude oil and natural gas and all of it is found inside rocks beneath the earth’s surface, i.e., in the crust.
Asset – Any area where ONGC has found oil and is currently producing it to surface through wells. Basin, when it starts generating revenue or is monetized, becomes an Asset.
Plant – Installations, similar to a refinery, where processing of crude oil and natural gas is done before being sold to industries, refineries, gas distribution companies like GAIL, etc.
Service – As the name suggests, provide specialized services to exploration and production activities of ONGC.
Institute – Here, domain-specific R&D work is carried out to support teams in Basin, Asset, Service, or Plant.
Corporate Services – Facilitate overall running of ONGC by providing all kinds of support to the Organizations’ workforce.
Office vs Field Posting
Any post will have either an Office or Field posting. Office comes with a General Duty pattern while Field comes with a Shift Duty pattern.
In field posting, your work location will be either a rig, processing platform, Complexes where oil from multiple wells is collected and processed, i.e. GGS or GCS, a plant, a Geophysical service part,y, etc. In office posting, your work location will be base office.
Generally, in the field, data is collected and plans are executed, whereas in Office, data is interpreted and plans are made.
Fig – One of the base offices in Mumbai
Fig – Drilling Rig in Rajahmundry
Offshore vs Onshore Posting
As explained earlier, oil can be found in rocks below the seafloor, so Offshore, and oil can also be found in rocks below land, so Onshore.
In Offshore posting, your posting location will be either Mumbai region (Western Offshore or West Coast) or Kakinada region (KG-PG or East Coast). All other locations entail an Onshore posting.
Fig – Processing installation/ platform in Offshore
Fig – Processing installation in Onshore
 – WORK PATTERN
Following are the various type of work pattern in ONGC:
2+2 – Is a shift based pattern, Involves 2 days of work (12 hrs each), 1 day shift and 1 night shift, then 2 holidays.
6+2 – Shift based, Involves 6 days of work (8 hrs each), 2 day shift then 2 evening and 2 night, then 2 holidays.
14+14 – Shift based, Involves 14 days of work (12 hrs each), 7 day shift and 7 night, then 14 holidays.
General Duty – Conventional office duty, Involves 5 days of work (8 hrs each), then 2 holidays.
- In Offshore posting, the pattern will definitely be 14 + 14. If posted in Institutes or Offices, pattern will definitely be General Duty.
- Posts like MMO, Transport Officer, AEE (Industrial Engg.) and Programming Officer will always have General Duty i.e., always office posting. All other posts can have field posting.
 WORK PROFILE
The work profile of different posts in ONGC through the GATE exam.
- Geologist: There can be a wellsite geologist working in rigs, carrying out jobs like analyzing drill cuttings, picking casing and coring points, well log interpretation, etc., and a Geologist in Office helping with the interpretation of geophysical information, making GTOs, etc.
- Geophysicist (Surface): In a basin and field posting, they carry out surveys like seismic, gravity and acquire other geophysical data while in Office they are involved in processing and interpretation of Geophysical data on a computer and identifying locations for probable oil accumulation.
- Geophysicist (Wells): In a field posting, they acquire wireline log data from a well under drilling, while in Office they are called Petrophysicist and help with interpretation of sub-surface data.
- AEE (Drilling): The most infamous of all, In field, they work in rigs and drill wells. As simple as it sounds, in reality, it’s tough. They have to monitor various parameters and ensure that a well is drilled to its target depth and location. In Office, they prepare drilling plans, manage rigs, etc.
- AEE (Cementing): Whenever a well is drilled, there’s a pipe called casing inserted in the well to prevent it from collapsing or caving. Their role is to cement that casing so that it remains intact. So in field, they work in rigs and do cementing, whereas in Office, they make plans and ensure maintenance of cementing units, etc.
- Chemist: In field, they work in drilling fluid services and have a vital role during drilling of a well. They can also be posted in processing installation and carry out tests on the quality of crude oil or gas. In Office, they can be posted in labs and carry out R&D work.
- AEE (Reservoir): I could write a separate answer on this. Only when posted in MH Asset can they have field + Offshore posting otherwise Office posting always. The rock from which oil is produced is called a reservoir. They use the data available from various studies carried out in wells like pressure measurement, core analysis, logs, etc., to answer ques like how much oil is there, whether economical to produce, identify ways to produce till the last drop, etc.
- AEE (Production): The post with the highest no. of personnel and most versatile profile. Their primary role is to maintain oil production from wells and study any decline and work to arrest that. In rigs, they carry out services like WSS, Well Completion, Workover, Wireline, etc. In plants, they handle the control room. In assets, they work in Surface Team and are posted in processing installations to maintain production levels, maintenance of artificial lift systems. They can also be posted in pipeline department and carry out pigging of flowlines.
- AEE (Electrical): In field, they can work in platforms/ installations where they will handle generators e.g., Gas Turbine generators in Offshore, electrical equipment having motors, SCADA systems UPS. In rigs looking after maintenance and working on advanced automation and PLC control system etc. In office, project management and design aspects of equipment, In Assets, they can be in maintenance department, etc. In short, all three aspects i.e., Generation, Transmission and Distribution is present.
- AEE (Instrumentation): They are part of the maintenance team and handle the instrumentation e.g., sensors in any plant/installation/ rig etc. They handle maintenance of flow meters, temperature sensors, manifold separators parameters, etc. Periodic checking of Instrument panel, installing new devices, etc.
- AEE (Electronics): In field and Office both their main role is to maintain communication systems like RTU, SCADA, and telecommunications (C-band, Ku-band, VHF, etc.). They also handle maintenance of telephone lines on platforms as well as CCTV and Paging Systems. In seismic survey party they handle sensors and geophones and their maintenance. The majority are part of the Info-com department.
- AEE (Mechanical): In field or Office, they are a part of the maintenance team. In Offshore ,e.g. they can be posted in rigs or platforms where they handle pumps, compressors, cranes, AC, etc. In Engineering Services they handle design and specification of machinery which ONGC intends to purchase. They can be posted in workshops handling maintenance of engines etc.
- AEE (Civil): If posted in Offshore Engg in Mumbai, it involves designing Offshore Platforms using modeling software and based on structural and geotechnical engg. In IEOT Panvel, R&D work related to Offshore construction is done. If posted in Office e.g., in an Asset, work can involve colony maintenance, handling tenders, etc. Whenever a well is drilled using a rig, site for rig activity i.e., drillsite preparation like approach roads, conductor casing installation is done by them.
- MMO: They are involved in contract management, procurement of materials for various activities and hiring of services through tenders. Handling post contract issues like termination etc. Working in stores and keeping records of incoming and outgoing goods using SAP. These days there is a widespread use of the GeM (Government e-Marketplace) portal.
- Programming Officer: Geoscientists work with software for carrying out interpretation of data, a PO helps in procuring those software and provides support for them too. ONGC has a data center running supercomputer at GEOPIC, they can work on that. They are in the SAP team. They maintain individual intranets of different Assets, work on small-big applications running on web servers/standalone for need-based solutions, work in Project ICE, etc.
- Transport Officer: They handle Logistics and Logistics plays a crucial role in ONGC. They handle ONGC’s fleet of vehicles (cars, buses, heavy vehicles, cranes, tractors, etc.), the large number of vessels (MSVs, OSVs, etc.) deployed in Offshore. They play a vital role in Heli-base like Juhu Helibase and Supply base like Nvaha Supply Base. Pipelines in Offshore also come under Offshore logistics.
- AEE (Industrial Engg.): Hiring for this post started from GATE 2019, IE profile is similar to HR profile. They can be posted in Employee Relations, Corporate Administration, Industrial Relations, etc. departments. They play a vital role in the Corporate R&P department which is responsible for recruitments like GT etc.