Growing numbers of projects are proposing to produce fluids contaminated with Hydrogen Sulphide (H2S) at high concentrations, and operating at high pressures.

The scale of toxic impact from high pressure, high-% H2S leaks is very significant, and this is driving changes to layout strategy. Large separation distances are being implemented in order to mitigate toxic fatality impact, particularly for simultaneous production and construction / maintenance operations (SimOps). A new methodology for layout has been developed for SimOps in high-sour facilities, based on "time to protect", which provides a risk-based approach to equipment or area segregation that buys time for emergency escape prior to impairment by incoming H2S. The methodology combines physical effects modeling and QRA, emergency response, and the "sour mindset" competency of personnel in response to an H2S release. It can also be used as a decision-making tool to determine the level of H2S training required and personal protection (such as escape breathing sets) for different SimOps areas and activities around a facility.

There is potential for application of the layout methodology in development of projects that will handle H2S at high partial pressures, such as:

  • Sour Enhanced Oil Recovery (EOR)

  • Acid Gas Injection (AGI)

  • Sour gas processing facilities with high-% H2S in the feed stream.

The material is applicable in both on- and offshore locations. The result is a layout that has significantly larger spacing than seen in "standard" facilities. There are many cost, schedule, operability and maintainability implications to consider; the ALARP balance is not simple. This type of layout approach requires front-end implementation in projects and early operations input in order for optimal benefits to be achieved.

The layout methodology can help to significantly reduce toxic exposure fatality risk, particularly for groups of workers. This can reduce a company's risk of reputation loss associated with large-scale multiple fatality accidents; a key factor for consideration in a sour venture where a large-scale H2S release can rapidly engulf a widespread area with toxic gas.

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