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Client: OMV
Location: Kurdistan Region, Iraq

Gas dispersion risk reduction.

Xodus Group experts conduct fire and gas dispersion studies and identify potential hazards on the Bina Bawi field.

Challenge
OMV Exploration & Production GmbH previously conducted petroleum exploration, appraisal and pre-development activities in the Bina Bawi block, 60km from Erbil in the Kurdistan region of Northern Iraq. Well tests from Bina Bawi 3 (BB-3) indicated a very sour oil reservoir with concentrations up to 190,000ppm hydrogen sulfide (H2S) and 50,000ppm carbon dioxide (CO2) in the gas phase.

There is no gas market available in the Bina Bawi license block so sour gas will be flared during the limited well testing period. For the intended longer production period, sour gas will be treated and injected into a suitable formation.

The development of the Bina Bawi field required a strategy to handle sour gas in the reservoir fluid. H2S is toxic by inhalation and can be fatal at atmospheric conditions as low as 500ppm. OMV requested Xodus Group analyse the potential loss of containment events and the resulting gas dispersion over a flat landscape to provide input to the layout of the facilities.

Assignment scope
During dispersion modelling it was noted that the landscape was not level – there are very pronounced ridges and valleys in the area of the Early Processing Facility (EPF). This had a significant bearing on the interpretation and use of the dispersion modelling which we took into account.

We developed six distinct release cases using DNV’s Phast consequence modelling software, including:

  • Uncontrolled well release scenarios caused by a rupture at the sour gas flowline
  • Gas releases that could occur from gas processing vessels or piping located on the facilities area
  • Potential hazard area from gas that is flared from High Pressure (HP), Low Pressure (LP) and a combination of HP and LP
  • Hydrocarbons release that could occur from piping and storage tanks located in the storage area.

Using dispersion modelling, we identified that, for the major release scenarios, the gas plume rises above ground height after some dispersion has occurred at ground level. Upon completion of the study, we identified that the risks of handling toxic gases required the use of substantial engineering and management system solutions.

Risk reduction techniques include:

  • H2S training
  • H2S zoning
  • Provision of toxic gas detection and escape breathing air sets
  • Medical facilities
  • Heating, Ventilation and Air Conditioning (HVAC) on buildings.

We also carried out a Hazard Identification (HAZID) study to identify the key issues and to confirm that the significant execution and operational safety hazards have all been identified and be suitably addressed. The gas dispersion studies were a key input to the HAZID meetings.

Results

  • Professional studies conducted where Xodus Group offered a high quality safety and flow assurance team
  • Potential hazards and the consequential effects on the facility highlighted
  • Risk reduction techniques identified.