HAZOP and SIL Study for Immiscible Gas Injection Project at Khoraghat GGS-1.  

Oil and Natural Gas Corporation Limited owns Khoraghat field located 110 km SSW of Jorhat town of Dhansiri valley area. Production from Khoraghat field is collected and processed at Khoraghat GGS-1. Well fluid (condensate / gas) from these fields are routed through inlet header & bath heater to a vertical two phase separator working on a level control. Separated condensate is routed to existing oil storage tank.

Separated gas is routed to Fuel gas scrubber / KOD and thereafter, fed to Fuel gas header under pressure control. Part of the fuel gas is used for bath heater as heating medium. Balance fuel gas is routed to AGCL (after fuel gas conditioning having scrubber & filter). Surplus gas produced if any, is flared.

ONGC Ltd. intends to recover the surplus gas which is being flared by installing a Compressor Package at Khoraghat GGS-I for immiscible gas injection in KH-1 & KH-5 wells at Jorhat Asset.

Gas injection to these wells helps to maintain the reservoir pressure and to increase the production. The envisaged gas injection quantity is 1.0 LSCMD (0.5 LSCMD in each well) at an injection pressure of around 230 kg/cm2g at well head.

The Produced gas from existing facility will be routed to the Compressor package for gas compression. In compressor package, the gas shall be compressed from 2.5 kg/cm2g to 260 kg/cm2g. Compressor package consists of 4 stage reciprocating compressors with a capacity of 1 LSCMD at the discharge.

The Scope of the Project is to Conduct HAZOP & SIL Study for Reciprocating Compressor Package.


The objective of the HAZOP study was to identify hazard and operability problems and to reduce the probability and consequences of an incident in the onshore facilities of Khoragahat GGS-1 in Oil and Natural Gas Corporation (ONGC) that would have a detrimental impact to the personnel, plant, properties and environment.

Methodology of HAZOP

  • Node Marking  based on Stream, equipment or a Package, on the P&ID
  • List the intention & process parameters, guidewords for the node
  • List all deviations and ignore deviations that are not meaningful and Apply the deviation
  • Brainstorm and list various causes of the deviation and ignore causes that are not credible
  • Determine the consequences of the deviation due to each listed credible cause
  • Identify Safeguards already provided in the system
  • Identify Risk Matrix based on severity & likelihood
  • Suggest recommendations / actions, should the safeguards be inadequate

Methodology of SIL

  • Identification and Mark up of SIF Loops in P & ID based on HAZOP Study.
  • List the Severity based on the Risk Matrix.
  • Brainstorm and list all the Enabling event and IPL for the SIF Loop in LOPA Sheet.
  • Assess the SIL rating and Suggest recommendation, should the safeguards be inadequate.