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Fire, Gas Dispersion, Explosion Analysis (FGDEA) and Hazardous Area Classification (HAC) for the Wells in the Kauther Gas Lift Project

Elixir Engineering  was awarded to perform Fire, Gas Dispersion & Explosion Analysis (FGDEA) and Hazardous Area Classification (HAC) for the wells in the KAUTHER GAS LIFT PROJECT

Project Summary

KGP fields are rich retrograde condensate gas reservoir. As there was a need to extend well life to reduce deferment and improve UR by improving well outflow and reduce OPEX and flaring associated with unloading restoration operations. Gas lift combined with Velocity string VS was determined the best solution for kick-off and for continuous lifting purposes. Accordingly, Rock International intended Elixir Engineering to perform Fire, Gas Dispersion & Explosion Analysis (FGDEA) and Hazardous Area Classification (HAC) for wells in Kauther Gas Lift Project.

Methodology

Hazardous Area Classification (HAC)

The evaluated separation of a facility into hazardous and non-hazardous regions, as well as the segmentation of the hazardous sections into zones, is known as area classification. A hazardous area is characterised as a three-dimensional place where it is reasonable to assume the presence of a flammable atmosphere at frequencies that necessitate extra care in the design and construction of equipment as well as the management of other potential sources of ignition.

Zone Classification: Hazardous areas are divided into zones based on the likelihood of occurrence and duration of a flammable atmosphere.

Zone 0: That portion of a dangerous location where there is a constant or prolonged presence of combustible air.

 Zone 1: The portion of a dangerous location where flammable air is most likely to occur during regular operations.  

Zone 2: That part of a hazardous area in which a flammable atmosphere is not likely to occur in normal operation and, if it occurs, will exist only for a short period.

Non-hazardous areas: Areas not covered by any of the aforementioned .

Grade and source of release: A source of release is any location from which a flammable gas, vapour, or liquid may be released into the atmosphere for the purposes of area classification. Based on their expected frequency and duration, three release grades are determined.

Continuous grade release: A release that happens regularly and at brief intervals, or that is almost continual .

Primary grade release: A release that is anticipated to happen in operational procedures that is likely to happen regularly or periodically throughout normal operation.

Secondary grade release: A release that is unlikely to happen during regular operations and, in any case, will only happen occasionally and briefly.

Fluid Categories:

FluidDescription
AA combustible liquid that would quickly and significantly evaporate upon discharge. This category includes:
a) Any liquefied petroleum gas or lighter flammable liquid.
b) Any combustible liquid that, when released, vaporises at a temperature high enough to create more than 40% of its volume without the addition of external heat.
BA combustible liquid that isn't in category A yet is hot enough to boil when released.
CA flammable liquid, not in categories A or B, but which can, on release, be at temperature above its flash point, or form a flammable mist or spray.
G(i)A typical methane-rich natural gas.
G(ii)Refinery hydrogen.

Vent Dispersion Study

The Objectives of the FGDEA are to carry out dispersion and thermal radiation assessment to ensure the distance from the wellhead/RMS manifold and the vent heights to the fence is adequate. The following leak sources are considered for the modelling

  1. Well head and RMS manifold
  2. Drain Pit Vent
  3. RV Vents

Overview

The FGDEA is a structured and systematic study to identify and assess credible fire and explosion hazards and ensure the facility layout eliminates the potential for escalation as far as reasonably practicable. This involves performing physical effects modelling (PEM) to assess the impact of credible leaks and assess the potential for escalation as per PDO SP-1258 (Quantitative Risk Assessment Specification). The study quantifies the physical effects of hydrocarbon releases, as defined by the potential sources of leakage (PSLs) and assesses the potential for impact on personnel due to flammable releases.

The physical effects modelling carried out as part of the FGDEA will be used to optimize the safe distance as per project scope to mitigate escalation and achieve an inherently safe plot, as far as practicable, based on PDO SP-1127.

Steps

  • Vent modelling
    • Calculate the required fence distance and vent height to achieve the heat radiation criteria (5Kw/m2 at property fence) using Gas Jet Flame Module.
    • For the Vent height calculated in Step-1, carryout flammable gas and H2S dispersion analysis to ensure that the calculated height also meets the gas exposure limits at facility fence to ensure that personnel working inside fence are not exposed to flammable/ toxic gas.
  • Leak Modelling
    • Obtain composition and flowrates from Process for the RMS and Wellhead for new wells
    • Carry out leak modelling for the 22mm.
    • Analyse flammable dispersion for 100% LFL to assess whether the required distance to the fence is safe from the source of leak.

Deliverables:

Hazardous Area Classification Report compiled with Zone Maps, Documentation of Hazardous Materials, Safety Recommendations. FGDEA Report compiled with Vent Design Recommendations, Contour Maps, Emergency Response Guidelines, Mitigation Measures, and Risk Assessment

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