Interview experience
ONGC interview experiences covering Computer-Based Test (CBT), Personal Interview, Document Verification + Medical Exam. Round-wise notes, common questions, and what candidates report clears each stage.
ONGC Interview Questions and Answers (2026)
Oil and Natural Gas Corporation is India's Maharatna upstream oil and gas public sector company. Freshers join as Graduate Trainees in Class-I executive roles after GATE-linked or company-specific selection. ONGC offers engineering careers in exploration, production, and refinery operations across India.
Explore: Interview experience · HR interview questions · Overview · Placement papers · Preparation guide
Overview
ONGC now recruits fresher engineers and geoscientists at E1 level (AEE, Geologist, Geophysicist) through its own Computer-Based Test, not GATE. Its 2025 and 2026 advertisements both use the CBT; the last GATE-based Graduate Trainee cycle was in 2022.
HR interview questions
ONGC HR interview questions with sample answer frameworks - motivation, relocation, STAR stories, and culture-fit prompts.
ONGC interview process at a glance
| Round | Duration | What they test |
|---|---|---|
| Computer-Based Test (CBT) | 2 hours | Domain (40Q), aptitude (25Q), general awareness (10Q), English (10Q); 85 questions, no negative marking |
| Group Discussion (may be held) | - | Not qualifying in the 2026 advertisement |
| Personal Interview | 15-25 min (candidate reports) | Core discipline fundamentals, PSU/field-work suitability (1:5 shortlist, 15 of 100 marks) |
| Document Verification + Medical Exam | - | Eligibility proof, fitness for field/offshore postings |
ONGC recruitment exam (CBT): quick answers
These answers come from ONGC’s official advertisements Advt. 1/2025 (R&P) and Advt. 2/2026 (R&P), the two most recent fresher E1 cycles. Both use the same CBT pattern. Routes can change between cycles, so the advertisement for your post is the final word.
| Question | Answer |
|---|---|
| How many questions and how long? | 85 multiple-choice questions in 2 hours: 40 from your domain, 25 aptitude, 10 general awareness and 10 English. PwBD candidates may get 20 minutes per hour extra. |
| Does it have negative marking? | No. Both the 2025 and 2026 advertisements say so. Attempt every question. |
| Is GATE required? | No. The 2025 and 2026 cycles use ONGC’s own CBT. The last GATE cycle (Advt. 6/2022, GATE 2022) used GATE 60, qualification 25 and interview 15. |
| How much is the cutoff? | No merit cutoff is published in advance. The minimum qualifying mark in the CBT is 45% for General, EWS and OBC and 40% for SC, ST and PwBD. |
| How many are called for interview? | 1:5 by CBT score within each category. Ties at the cut-off mark are all called. |
| How much does the interview count? | 15 of 100 marks, with the CBT carrying 85. You must also qualify the interview: 9 of 15 for General, EWS and OBC, 6 of 15 for SC, ST and PwBD. |
| Is there a medical test? | Yes. Appointment depends on passing ONGC’s Medical Examination of Employees Rules, and many postings are on field, drilling or offshore assets. |
| Which disciplines were recruited? | 2025: Mechanical, Petroleum, Chemical and Electrical AEE posts plus Geology and Geophysics (108 posts). 2026: Petroleum, Mechanical, Chemical, Instrumentation and Geology (52 posts). Both need 60% in the degree. |
ONGC interview questions by discipline
The interview follows the post you applied for. These are questions candidates reported in older public blog composites (2018, AEE Production and Drilling) and a 2023 LinkedIn account (CSE); no public 2025-26 CBT-cycle interview accounts were found. They show the level, not a fixed list.
| Discipline | Reported questions and topics |
|---|---|
| Mechanical (AEE Production / Drilling) | Centrifugal vs reciprocating pumps, which pump for high head, cavitation. Second law, latent heat, modes of heat transfer. TIG welding, soldering vs brazing, annealing, cladding. Boilers, cooling towers, bearings, octane and cetane numbers. |
| Petroleum / Chemical | Petroleum and chemical fundamentals, CNG vs LNG vs LPG and their storage, situational problem-solving. Expect drilling mud, well types and recovery methods. |
| CSE (Programming Officer, GATE-era post; not in the 2025 or 2026 CBT ads) | Database types, RDBMS vs non-relational, normal forms, how to store mobile numbers (string, uniqueness, indexing), basic LLM awareness, final-year project. |
| Electrical (2025) / Instrumentation (2026) / Geoscience | Few public reports. Expect core subjects of your degree at CBT depth, plus your project and training. |
Asked across every discipline: introduction and hometown, your project and industrial training, why ONGC and why the public sector, India’s crude import dependence and OPEC, refinery or site safety situations (such as a fire in a room with smoke sensors), and whether you accept field, northeast or offshore postings.
Computer-Based Test (CBT)
ONGC’s own screening exam, which replaced GATE shortlisting from the 2025 cycle: 85 multiple-choice questions in 2 hours with no negative marking, split across your concerned engineering/geoscience domain (40 questions - the largest single section), aptitude (25), general awareness (10), and English (10). The CBT carries 85 of 100 marks in final merit, so it does most of the actual selecting. The 2025 and 2026 advertisements set minimum qualifying marks in the CBT of 45% for General/OBC/EWS and 40% for SC/ST/PwBD, followed by a 1:5 shortlist per category for the Personal Interview. Multi-session exams are normalised, so raw marks alone do not decide rank.
Common questions
- Domain-specific questions at B.E./B.Tech curriculum depth for your discipline (Petroleum, Mechanical, Chemical, Instrumentation, Geology, etc.)
- Quantitative aptitude and logical reasoning
- General awareness - current affairs, energy sector, ONGC-relevant topics
- English comprehension and grammar
Personal Interview
Shortlisted at 1:5 on CBT score, candidates then go through a Personal Interview worth 15 of 100 marks, with a separate qualifying mark of 9 of 15 (6 of 15 for SC/ST/PwBD). It goes deep on your core discipline and probes genuine suitability for a PSU role that can involve field, drilling, or offshore postings.
Common questions
- Core technical questions from your engineering/geoscience discipline
- Detailed walkthrough of your final-year project - methodology, results, design choices
- What do you know about ONGC’s exploration and production operations?
- Are you willing to work at field sites, drilling locations, or offshore platforms, and why?
Sample answer frameworks are on the ONGC HR interview questions page.
Document Verification and Medical Examination
The final stage before appointment: document verification against your application and category/eligibility claims, plus a mandatory medical fitness examination - a real gate given that many ONGC postings involve physically demanding field, drilling, or offshore work.
Common questions
- Verification of educational certificates, category certificates, and other eligibility documents
- Standard medical fitness parameters relevant to field/offshore posting eligibility
Why the screening route matters here
Unlike most companies covered on this site, ONGC’s screening mechanism for fresher E1 hiring has genuinely changed: GATE-score shortlisting up to the 2022 Graduate Trainee cycle, then its own in-house CBT in the 2025 and 2026 cycles. This isn’t a stylistic detail; it changes what you should actually be studying and when. Before you commit prep time, check the live ONGC recruitment notification (advertisement number, not a summary blog) for your specific cycle and discipline to confirm which route is active and what the current CBT syllabus and weightage are.
ONGC CBT route vs GATE route
ONGC has used two screening routes for the same entry-level E1 posts. The 2025 and 2026 cycles use ONGC’s own CBT (85 questions, 85 of 100 marks) followed by an interview worth 15. The 2022 and earlier Graduate Trainee cycles shortlisted on GATE score, and merit combined GATE, qualification marks and the interview.
| CBT route (2025, 2026) | GATE route (up to 2022) | |
|---|---|---|
| Written filter | ONGC’s own CBT | GATE score in the mapped paper |
| Merit split | 85 CBT + 15 interview | 60 GATE + 25 qualification + 15 interview (2022 ad) |
| What to study | Domain plus aptitude, GA and English | GATE syllabus only |
This page covers the CBT route used in 2025 and 2026. If a future advertisement names GATE again, use the GATE split instead and ignore the CBT sections.
Common technical interview questions and answers
Q: What is the difference between exploration, appraisal, and development wells?
An exploration (wildcat) well is drilled into an untested prospect to establish whether hydrocarbons are present at all, and carries the highest geological risk. An appraisal well follows a discovery and is placed to delineate the reservoir’s extent, fluid contacts, and rock quality so reserves can be estimated with confidence. A development (production) well is drilled inside a proven, delineated field purely to produce hydrocarbons at planned rates. ONGC’s E&P business runs all three, and interviewers often ask this to check that you understand the sequence from prospect to production rather than just the drilling mechanics.
Q: Why is drilling mud used, and what happens if its density is wrong?
Drilling mud performs four main jobs: it exerts hydrostatic pressure to balance formation pore pressure, carries rock cuttings up the annulus to surface, cools and lubricates the bit, and forms a filter cake that stabilises the borehole wall. If mud weight is too low, formation pressure exceeds well pressure and formation fluid enters the wellbore - a kick, which if uncontrolled becomes a blowout. If mud weight is too high, it can exceed the formation fracture gradient and cause lost circulation, where mud escapes into the formation and the resulting drop in the mud column can itself trigger a kick. The safe operating band between pore pressure and fracture gradient is the drilling window.
Q: What is enhanced oil recovery, and how does it differ from secondary recovery?
Primary recovery uses the reservoir’s own natural energy - solution gas drive, gas cap expansion, water drive - and typically recovers only around 10-20 percent of oil in place. Secondary recovery restores reservoir pressure and sweeps oil by injecting water or immiscible gas, commonly lifting recovery to roughly 30-40 percent. Enhanced oil recovery (tertiary) changes the fluid properties or rock-fluid interaction rather than just pushing oil: thermal methods such as steam flooding reduce viscosity, miscible CO2 or hydrocarbon gas injection eliminates interfacial tension, and chemical methods use polymers to improve mobility ratio or surfactants to reduce interfacial tension. ONGC has run large water-injection and EOR programmes on mature fields such as Mumbai High, so the practical motivation - arresting decline in an ageing field - is worth stating.
Q: State the first and second laws of thermodynamics and what each actually constrains.
The first law is conservation of energy: for a closed system, dU = Q - W, meaning the change in internal energy equals heat added minus work done by the system. It constrains how much energy exists but says nothing about direction. The second law introduces entropy and states that the total entropy of an isolated system never decreases, which is why heat flows spontaneously from hot to cold and why no cyclic engine can convert heat entirely into work. It sets the Carnot limit on thermal efficiency, 1 minus T_cold divided by T_hot with temperatures in kelvin, which is the ceiling any real turbine, pump driver, or gas-processing cycle is measured against.
Q: What is cavitation in a centrifugal pump and how do you prevent it?
Cavitation occurs when the local static pressure at the pump suction falls below the liquid’s vapour pressure, forming vapour bubbles that then collapse violently in the higher-pressure impeller region. The collapse pits the impeller metal, causes noise and vibration, and destroys head and efficiency. The governing condition is that available NPSH must exceed required NPSH with a safety margin. Prevention means raising available NPSH - increase suction static head or lower the pump relative to the source, shorten and enlarge the suction line to cut friction losses, reduce liquid temperature to lower vapour pressure, or select a lower-speed or double-suction pump with a lower required NPSH.
Q: Why is power transmitted at high voltage, and what do transformers do about it?
For a given transmitted power P at voltage V, the line current is P divided by V, and resistive line loss is I squared times R. Raising the transmission voltage by a factor of ten cuts the current to a tenth and therefore the ohmic loss to a hundredth, which is why bulk transmission runs at 220 kV, 400 kV, or 765 kV. Transformers make this practical: step-up units at the generating station raise voltage for transmission and step-down units at substations reduce it for distribution and utilisation. High voltage also reduces the conductor cross-section needed, but is limited by insulation cost, clearance requirements, and corona losses.
Q: What is a PLC, and where would it be used on an ONGC installation?
A Programmable Logic Controller is a ruggedised industrial computer that scans input signals from field devices, executes a user program (classically ladder logic) each scan cycle, and drives outputs to actuators - all with deterministic timing and tolerance for heat, vibration, and electrical noise. On a rig or process platform it runs sequencing and interlock logic for pumps, compressors, separators, and valve line-ups, feeding a SCADA/DCS layer for operator visualisation. Safety-critical functions such as emergency shutdown and fire-and-gas detection are typically handled by a separate, certified Safety Instrumented System rather than the basic process control PLC, so that a control fault cannot disable protection. Knowing that separation of control and safety layers is what distinguishes a prepared instrumentation candidate.
Q: What are source rock, reservoir rock, cap rock, and trap - and why do you need all four?
Source rock is organic-rich shale in which kerogen matures into hydrocarbons under heat and pressure. Reservoir rock, typically sandstone or carbonate, has the porosity to store those hydrocarbons and the permeability to let them flow. Cap rock (seal) is an impermeable layer such as shale, salt, or tight limestone that stops buoyant hydrocarbons migrating further upward. A trap is the geometry - structural, like an anticline or fault block, or stratigraphic, like a pinch-out or reef - that concentrates hydrocarbons into a producible accumulation. All four plus correct timing of migration relative to trap formation must coincide; if any element is missing, the prospect is dry, which is why exploration wells fail even over good source kitchens.
Q: What is ONGC Videsh, and why does India still import crude if ONGC produces domestically?
ONGC Videsh Limited (OVL) is ONGC’s international E&P arm - it invests in overseas blocks and equity oil to supplement domestic production. India still imports a large share of crude because domestic output meets only a fraction of total demand; ONGC is the largest domestic producer but national consumption outstrips it. Interviewers use this to test energy awareness, not memorised slogans - cite the dependency idea honestly rather than pretending self-sufficiency.
Q: What HSE basics should a fresher know before a field or offshore posting?
At minimum: permit-to-work, hierarchy of controls (eliminate → engineer → admin → PPE), hot-work and confined-space awareness, gas detection on rigs, and emergency muster / fire-response basics. Panels sometimes ask situational questions (“fire in this room - first step?”) to see if you think about alarms, evacuation, and not heroic solo fixes. Willingness to follow strict procedures matters as much as textbook thermodynamics for PSU field roles.
Frequently asked questions about ONGC interviews
Does the ONGC CBT have negative marking?
No. ONGC’s official advertisements for its CBT-based E1 recruitment (Advt. 1/2025 and Advt. 2/2026) both state there is no negative marking. The paper has 85 multiple-choice questions in 2 hours: 40 concerned domain, 25 aptitude, 10 general awareness and 10 English.
What is the ONGC CBT cutoff?
ONGC does not publish a merit cutoff in advance. Its 2025 and 2026 advertisements set minimum qualifying marks in the CBT of 45% for General, EWS and OBC and 40% for SC, ST and PwBD, then shortlist about 1:5 per category by CBT score for interview. Multi-session exams are normalised. The interview has its own qualifying mark: 9 of 15 for General, EWS and OBC and 6 of 15 for SC, ST and PwBD.
What is the ONGC interview process for freshers?
ONGC’s current fresher E1 process (AEE, Geologist and Geophysicist posts) has 3 stages: ONGC’s own CBT, a Personal Interview, and document verification plus a medical exam. 1. CBT - 85 multiple-choice questions in 2 hours: concerned domain (40), aptitude (25), general awareness (10) and English (10), with no negative marking. 2. Personal Interview for candidates shortlisted at about 1:5 by CBT score; the 2026 advertisement adds that a Group Discussion may be held but is not qualifying. 3. Document verification and a medical exam under ONGC’s medical rules. Final merit is CBT 85 + interview 15, and you must qualify both separately.
Does ONGC still hire through GATE, or is it a separate written exam now?
No. ONGC’s two most recent fresher engineer recruitments used its own CBT, not GATE: Advt. 1/2025 (R&P) for 108 AEE and geoscience posts, with the CBT on 23 February 2025, and Advt. 2/2026 (R&P) for 52 engineer and geologist posts, with the CBT on 6 September 2026 (tentative). The last GATE-based cycle was Advt. 6/2022, which filled 871 Graduate Trainee posts through GATE 2022 with merit of GATE 60, qualification 25 and interview 15. Check the advertisement for your cycle, since the route can change again.
What questions are asked in the ONGC interview?
The CBT tests your concerned engineering/geoscience domain (Petroleum, Mechanical, Chemical, Instrumentation, Geology, etc.), plus general aptitude/reasoning, general awareness, and English. The Personal Interview that follows focuses on core discipline fundamentals for your branch, awareness of ONGC’s exploration and production operations, and willingness to work at field sites, drilling locations, or offshore platforms. There’s no DSA/coding round - this is a technical-domain and PSU-fit evaluation, not a software-style interview.
How many rounds are there in the ONGC interview?
Two scored stages: the CBT (85 of 100 marks) and a Personal Interview (15 marks) for those shortlisted at about 1:5. A Group Discussion may be added but is not qualifying in the 2026 advertisement, and document verification and a medical exam follow before appointment at E1 level.
How should I prepare for ONGC interviews?
Focus first on the CBT - revise your specific engineering/geoscience domain deeply since it carries 40 of the 85 questions and 85% of final merit, alongside general aptitude, reasoning, general awareness, and English. For the Personal Interview, revise your core subjects further, read up on ONGC’s exploration and production business, and be prepared to discuss willingness to work at remote field, drilling, or offshore locations - a standard and genuinely important part of ONGC’s PSU hiring evaluation.
What ONGC interview panels score
ONGC E1 selection is not a coding campus loop. In the 2025 and 2026 CBT cycles the interview is worth 15 of 100 marks and has a separate qualifying mark of 9/15 (6/15 for SC/ST/PwBD). The 2022 GATE cycle used the same 15-mark interview alongside GATE 60 and qualification 25. Panels score:
- Core-discipline fundamentals tied to oil and gas (projects, numericals, HSE awareness).
- Honest field-posting willingness - assets pan-India, not only Dehradun or Mumbai HQ talk.
- Form consistency - application details, CBT and academic record, and “Why ONGC vs private” without memorized slogans.
Soft fail modes: treating the interview like BARC (where oral can dominate), refusing Assam/offshore talk after saying “anywhere,” or failing the medical after clearing merit.
Can a strong ONGC interview overcome a weak CBT score?
Rarely. The CBT carries 85 of 100 marks, so a great interview cannot close a large CBT gap. The interview still matters because it has its own qualifying mark (9 of 15 for General, EWS and OBC) - failing it removes you regardless of your CBT score.
How to prepare for ONGC interviews
- Loop map: Computer-Based Test (CBT); Personal Interview; Document Verification + Medical Exam. Confirm timings from the drive mail.
- Technical depth: Drill the Q&A section until answers are spoken, not read. Know every resume project cold.
- Experiences: Study round-wise notes on the interview experience page - real prompts beat generic lists.
- HR: Three STAR stories + a specific “Why ONGC?” on the HR page.
Who usually fits and who struggles
Good fit: You are already strong in your branch’s core subjects, you can live on an asset (shifts, heat, offshore talk), and you want a PSU engineering career more than a Bengaluru SDE.
Harder path: You prepared only coding. Or you want Mumbai-only posting. Interviewers have heard “I will go anywhere” from people who freeze when they hear Assam / Rajahmundry / offshore.
A practical ONGC prep plan
Use this as a default four-week loop before a ONGC drive. Adjust to your invite timeline.
- Week 1: CBT pattern first: sit one untimed paper, then redo it under the real 120-minute clock. Open the ONGC previous-year sets on this site and mark which sections ate your time. Write the timing on a sticky note. That number is more useful than a 200-problem LeetCode streak you never timed.
- Week 2: Most ONGC drives fail people on the first timed paper or OA. Do three timed sits this week. After each one, log every miss in a two-column note: topic and why (slow, wrong formula, bad edge case, panic). The next sit should only add problems from that log.
- Week 3: Technical interviews at ONGC usually want a clean project story, one or two CS fundamentals, and (if the process has it) a behavioral or values round. Write STAR stories on paper, not in your head. Practise “Why ONGC?” with one concrete product, lab, or business line - not a slogan.
- Week 4: Star stories + one project walkthrough recorded on your phone. If you still have energy, redo only the questions you failed in week 2.
10-day crash version: Days 1-4 timed domain + aptitude + GA + English mixes (not coding DSA), days 5-7 core discipline numericals + project walkthrough, days 8-9 mock PI out loud, day 10 field-posting honesty + HR STAR stories on the HR page.
Compensation notes
Candidate-reported fresher/early-career packages for ONGC often cite ₹20-26 LPA CTC · Posting: assets pan-India, not only Dehradun/Mumbai ·. Treat forum numbers as ranges, not guarantees - confirm the written offer letter for your team and location.
Sources
Interview process details and sample questions on this site are editorially organized from public candidate reports and hiring write-ups, with round structure, prep notes, and company-specific framing added by our team. For round-by-round stories, see the ONGC interview experience page. For OA papers and coding drills, use ONGC on placementpapers.app. CBT quick answers, the route comparison and the FAQs draw on ONGC’s official advertisements Advt. 1/2025 (R&P) and Advt. 2/2026 (R&P), Physics Wallah’s ONGC AEE 2025 and ONGC 2026 recruitment pages, and GATE Overflow’s copy of the Advt. 6/2022 GATE 2022 notification. Discipline-wise questions draw on the GateFlow blog’s 2018 ONGC AEE interview composites and a 2023 LinkedIn account of an ONGC CSE interview.
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