Introduction
Ensuring the safe handling, compression, and transportation of hydrocarbons is paramount to protect people, assets, and the environment. HAZOP (Hazard and Operability) Studies and SIL (Safety Integrity Level) Assessments are globally recognized methods to systematically identify potential hazards, assess operational risks, and implement risk reduction measures.
The studies were aimed at enhancing operational safety, improving plant reliability, and achieving compliance with international standards such as IEC 61508 and IEC 61511.
Methodology
The methodology adopted for gas gathering stations was systematic, structured, and consistent with international best practices:
The HAZOP study involved dividing process systems into logical nodes based on P&IDs for systematic analysis. Standard guidewords (e.g., No, More, Less) were applied to parameters like Flow and Pressure to identify deviations. Potential causes and consequences of these deviations were assessed for safety, environmental, and operational impacts. Existing safeguards, such as alarms and interlocks, were reviewed, and recommendations were made to address any gaps in safety measures.
The SIL study involved identifying Critical Safety Instrumented Functions (SIFs) based on HAZOP findings and Cause & Effect diagrams. Layer of Protection Analysis (LOPA) was used to assess the adequacy of existing safeguards and determine the need for additional risk reduction. SIL targets were assigned based on risk severity and likelihood, with a final verification to ensure risks were mitigated to acceptable levels.
Outcome
The HAZOP & SIL studies for gas gathering stations identified process hazards and strengthened safety barriers through improved alarm systems, shutdown systems, and interlocks. Recommendations included redundancy and fail-safe design enhancements in compressors and gas handling units. SIL classification optimized Safety Instrumented Functions (SIFs) for effective risk reduction. Overall, the studies improved plant reliability, operational safety, and compliance with HSE policies.
1. Oil India Limited Field Gas Gathering Station (FGGS) at Baghjan
Project Introduction:
Oil India Limited (OIL) developed a modular Field Gas Gathering Station (FGGS) at Baghjan, Upper Assam, with an initial processing capacity of 5.0 MMSCMD of non-associated gas, and provision for future expansion to handle increased gas volumes.
The HAZOP and SIL study covered the following units:
- Production and Test Manifolds for well fluid handling.
- Gas/Condensate/Water Separator Systems.
- Triethylene Glycol (TEG) Gas Dehydration Units.
- Effluent Treatment Plants and Disposal Systems.
- Utility Systems including Flare Systems and Fuel Gas Handling.
- Compressor Skids, Instrumentation Loops, and Shutdown System
Conclusion
The study effectively strengthened the overall safety framework of the FGGS facility, ensuring compliance with best practices in gas field development and production operations.
2. ONGC – Immiscible Gas Injection Project at Khoraghat GGS-1
Project Introduction:
ONGC implemented the Immiscible Gas Injection Project at Khoraghat GGS-1 to recover surplus gas, previously flared, and re-inject it into KH-1 and KH-5 wells to enhance reservoir pressure and maximize oil recovery.
The HAZOP and SIL study scope included the following:
- Four-Stage Gas Compression System with Inter-stage Knock-out Drums and Air Coolers.
- Gas Separation Systems including Inlet KOD and Stage-wise Separators.
- High-Pressure Gas Injection Systems connected to wellheads.
- Flare Gas Management and Fuel Gas Conditioning Units.
- Shutdown Systems, Control Logic, and Critical Alarm Systems for compressor protection.
Conclusion
The study played a vital role in enhancing the safe, efficient operation of the gas injection facilities, aligning with ONGC’s strategy for improved field recovery and environmental sustainability.