Safety and Design Verification Plan for Thamoud Infill Development Phase 3 Project

Project Summary

Elixir Engineering  was awarded to perform providing Thamoud West and Maurid NE fields necessary infrastructure / surface facilities to accommodate gross production demand according to the latest forecast and proposed FDP.

Maurid field which is split between Maurid (Main) & Maurid North East fields, is located on the eastern side of the South Oman salt basin NE of Salalah. Maurid North East (MDNE) field was discovered late 1997 with wells MDNE-1 and MDNE-2 discovering oil in the MG & LG and was brought on-stream in 1998.

Thamoud field which is split between Thamoud West and Thamoud East fields, is also located on the south-eastern margin of the South Oman salt basin. Maurid NE and Thamoud west fields are currently produced under waterflooding. The main producing reservoir associated with Maurid NE field is Ghariff formation and for Thamoud west field these are Ghariff and Al Khlata formations.     

Scope of Work

The Project scope is listed below,

MSVs, CS+HDPE liner/rotoliner MSVs to existing Manifold, Coriolis Meter + WC meter (Red Eye), 300# for well testing with Static Mixer and provision for Prover, common provision for Mobile Well Testing (PI Unit), Provision for future installation of static mixer and WC meter, concrete closed Relief/Maintenance Pit with Level transmitter, partial RVs (1W+1S), Demulsifier skid with Demulsifier storage tank in Manifold, RTU for the Demulsifier Skid, full flow RV on the test header.

The Scope of Elixir Engineering is to perform the listed safety studies for Thamoud Infill Phase-3 project.

Safety Studies
  • HAC Schedule
  • HAC Layout
  • Escape Route Layout
  • Safety Sign Layout
  • Safety Critical Element Identification (SCE) Report
  • HFE Verification Report
Hazardous Area Classification (HAC)

The process of dividing a facility into hazardous and non-hazardous sections and then further subdividing the hazardous parts into zones is known as area classification. A three-dimensional place that requires extra care in equipment design and construction as well as in controlling other potential ignition sources is known as a hazardous area classification (HAC). This is because flammable atmospheres are expected to be present there at certain frequencies

Zone Classification: Zones are created inside hazardous locations according to the probability and length of a flammable atmosphere.
Zone 0: The area of a dangerous area when there is a constant or prolonged presence of combustible air.
Zone 1: The portion of a dangerous location where the likelihood of a flammable environment during regular operations is high.
Zone 2: The portion of a hazardous location where there is little chance of a flammable environment during regular operations and, in the event that it does, it will only last briefly. Non-hazardous areas : Areas that do not fall into any of the above.

Source and grade of release: Any location from which a flammable gas, vapour, or liquid may be released into the atmosphere is considered a source of release for the purposes of area categorization. The expected frequency and duration of three grades of release are defined.
Continuous grade release: A release that happens often and at brief intervals, is virtually continuous, or is both. Primary grade release: A release that is planned for in operating procedures, meaning it is one that is expected to happen on a regular or infrequent basis during normal operation.
Release classified as secondary grade: One that, in any case, will only happen seldom and for brief periods of time and is unlikely to happen during regular operations

Fluid Categories:

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 has reached a temperature high enough to yield more than 40% volume vaporisation upon release and no external heat input. 
BA flammable liquid that does not fall under category A yet is hot enough to boil when released.
CAn ignitable liquid that does not fall under category A or B but that, upon release, may reach a temperature higher than its flash point or condense into a flammable mist or spray.
G(i)A typical methane-rich natural gas.
G(ii)A typical methane-rich natural gas.
Fire & Gas Dispersion Explosion Assessment (FGDEA)

By identifying and assessing potential fire and explosion hazards, the FGDEA seeks to ensure that the facility layout minimizes the probability of escalation to the greatest extent that is practically practicable. According to PDO SP-1258 (Quantitative Risk Assessment Specification), physical effects modeling (PEM) is used to assess the impact of credible leaks and ascertain the likelihood of escalation. According to the probable sources of leakage (PSLs), the study assesses the physical effects of hydrocarbon emissions as well as the possibility of harm to workers from flammable and hazardous releases. As far as is practical, the physical effects modeling completed as part of the FGDEA will be used to optimize the Dhiab Infill Development Project, mitigate escalation, and create an intrinsically safe plot based on PDO SP-1127 & SP-1190. It will also be used to confirm that the current Maintenance drain pit vent pipe layout is appropriate in accordance with DEP requirements

The objectives of this study is to

  • Determine all plausible hydrocarbon hazardous events (e.g., jet fire, flash fire, pool fire, flammable gas dispersion, and explosion);
  • Evaluate the effects of the final results resulting from releases;
  • Evaluate the toxic impacts in accordance with the requirements in SP-1190;
  • Evaluate the potential impact on adjacent units as well as buildings (if included in the project scope), taking into account the location of the potential releases;
  • Give a warning about the possibility of an explosion and fire escalation.
  • Determine protection / mitigation measures to prevent escalation as appropriate for the phase of development).

The overall study approach is summarised as follows

  • Develop assumptions;
  • Establish the assessment criteria;
  • Determine plausible risk scenarios and possible sources of leaks;
  • Launch the software, then determine the impact radius for flammable dispersion and unintentional ignition;
  • Report the outcomes for flammable dispersion and unintentional ignition.
  • Analyse the results against assessment criteria;
  • Provide the findings for every leak source together with the corresponding plausible scenarios;
  • Analyse the results against assessment criteria;
  • Conclude if the identified impact is acceptable and if the case recommend additional mitigation.
Hazard Identification
Event Tree for Process Hazards
Safety Critical Element Identification Report (SCE)

Any piece of hardware, structure, system, or logic software whose malfunction could result in a Major Accident Hazard (MAH) or whose goal is to stop, limit, or lessen the impacts of an MAH is referred to as a Safety Critical Element (SCE).

The identification of the Safety Critical Element (SCE) represents a critical step in project development that aims at minimizing the Major Accidental Hazards (MAHs) occurrence; this activity has to be performed from the beginning of the project and updated coherently with the developments throughout the life cycle of the project.

The aim of the present document is to provide the methodology used for the identification of SCE and eventually brief up the identified SCEs for the project. In order to identify the SCE, the basic principle followed is as given below:

  • Identification of Major Accident Hazards (MAH);
  • Identification of the SCE groups as per the standards; and
  • Summarizing the identified SCEs for the current scope.
Hardware Barrier and SCE Groups

The role of a preventive / mitigation barrier is to prevent threat and limit consequences of MAH. The purpose of this section is to ensure that all hardware barrier which are necessary to control MAH, are identified and the relevant SCEs are tabulated along with the tag No.

Hardware Barrier

High level grouping of SCEs utilized for reporting reasons is one of the hardware obstacles for MAH. There are 8 types of hardware barriers as depicted in the “Swiss Cheese Model”, shown the following figure - 2: Hardware Barrier and SCE Groups, which represents the two sides of bow-ties.

  • Structural Integrity (SI).
  • Process Containment (PC).
  • Ignition Control (IC).
  • Detection Systems (DS).
  • Protection System (PS).
  • Shutdown system (SD).
  • Emergency response (ER).
  • Life saving equipment (LS).

The hardware barriers are depicted with a number of small holes that represent a design flaw or some potential degradation of their performance. On their own, these degradations may not be significant but, if the holes line up, there may be no effective barriers in place between safe operations and escalating consequences, leading to MAH.

SCE Groups

Hardware barriers are separated into SCE Groups for the purpose of management and reporting. The role these Groups play in maintaining the barrier's integrity defines them.

Hardware Barrier and SCE Groups

SCE Selections

In general, the process of selection of SCEs start with a review of the generic list of SCEs as per the standards. SCEs selection process as represented below.

SCE Selection Process

HFE Design Verification (Define phase)

Design shall be reviewed to verify that it complies with the project HFE Design Verification HFE standards as defined in the project technical standards selection list and any HFE requirements identified through HFE studies conducted in the combined DEFINE and EXECUTE phases have been satisfied.

HFE Construction Verification (Execute phase)

Ensure that HFE requirements have implemented at site during construction phase as per recommendations from design verification, if any.

The verification review shall be done by the project HFE Authorized person and appropriate disciplines wherever applicable in line with SP-2215-1 Human Factors Engineering in projects – General Requirements.

HFE Process

HFE shall be initiated in the assess phase of projects, Figure 4 gives an overview of the HFE Activities in each of the ASSESS, SELECT, DEFINE and EXECUTIVE phase of the project life cycles.

Overview of Principal’s HFE activities by project lifecycle phase

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