MGP Brownfield Modification for Onshore Depletion Compression OQ project

Elixir Engineering  was awarded to perform MGP Brownfield Modification for Onshore Depletion Compression OQ Gas network

Project Summary:

The Bukha Field is located in Block 8 approximately 23 km offshore from the western coast of the Musandam Peninsula; with the Bukha Alpha platform some 23 km from the Musandam Gas Plant (MGP). Offshore Block 8, which contains the Bukha and West Bukha fields, produced an average of 4,458 barrels of oil equivalent per day during 2018. From January 2019, Block 8 is being operated by the MOGC (Musandam Oil and Gas Company), which is fully owned by MOGC (OQ E&P LLC).

All the production from Block-8 is being processed at onshore processing station i.e. Musandam Gas Plant “MGP”. The inlet arrival operating pressure to MGP is in the range of 15 – 18 barg (220 -260 psig) while downstream gas processing units require an operating pressure of 60 barg (870 psig). Inlet compressors available at the downstream of Slug-catcher (three machines each having a capacity of 20 MMSCFD) is used to boost the pressure from 15 Barg (220 psig) to required 60 barg (870 psig) (with compression ratio ~3.3). The configuration of Compressor shall be maintained in such a way that one compressor should be maintained in standby mode.

Presently, in order to achieve the inlet pressure at MGP (15-18 barg), the wells at Bukha are being operated at 22 barg (320 psig) and west Bukha operating at around 29 barg (420 psig) as shown in the block diagram below.

Production wells are under depletion mode and producing majorly gas and smaller quantity of condensate & water. To enhance the production at the MGP plant inlet, it is proposed to operate MGP plant inlet at reduced pressure of 4.5 barg from 15-18 barg. To facilitate the above proposal, different configuration of inlet gas compressor arrangements was studied part of the conceptual study and option 3A configuration was selected as feasible option. Following modification shall be required to integrate the project scope with existing plant for the reduced operating pressure of 4.5 barg at Slug Catcher A-1001 inlet.

Project scope:

Scope includes the installation of New piping Tie-in shall be made downstream of the particle Filter / Coalescer S-1501A/B for routing the gas to the new LP compressor K-1506A/B (1W+1S) suction via LP suction scrubber V-1506A/B. Gas pressure shall be raised from 3.15 barg at the LP compressor inlet to 17.92 barg to meet the existing Inlet Gas Compressor K-1501A/B/C inlet conditions. Existing inlet gas compressor K-1501A/B/C configuration shall be changed to (1W+2S) to meet the project scope. Gas pressure will be raised by K-1501A/B/C to 60.2 barg as per existing condition to meet the GSU battery limit requirement.

New tie-in shall be made for integrating the new Condensate Booster Pump P-1006A/B downstream of slug catcher A-1001 condensate common line. Condensate operating pressure will be raised from 4.5 barg to the existing operating pressure of 16.2 barg downstream of 10-LCV-001A. P-1006A/B discharge line will tie-in to the upstream of level control valve 10-LCV-001A. Produced water from the slug catcher is re-routed to the existing Skim system instead of connecting to the 10-LCV-001A downstream due to the low operating pressure of slug catcher A-1001.

A new tie-in shall be made to provide fuel gas blanketing for MP production separator with operating pressure of 13 barg (Operating pressure modified from 15.9 barg due to limitation of fuel gas supply pressure of 17.25 barg at E-3701 downstream) & continuous supply to pre-flash vessel to maintain the operating pressure at 12 barg.

Elixir Responsibilities:

Elixir Engineering done different safety studies for MGP Brownfield modification project. The safety studies conducted for this project scope is listed below:

Safety Studies:

  • Bow Tie
  • Constructability Review


Objective :

The intention of the Bow Tie exercise is to develop detailed / comprehensive Bow Tie diagrams which are to be dynamic in nature and can be regularly maintained by asset to reflect live status of each barrier condition. A Bow Tie diagram is a powerful tool for communicating how the control of major accident hazards is achieved.

Methodology :

The Bow Tie analysis will include Bow Tie diagram, for “each MAH scenario” presenting its causes (threats), consequences and potential escalation scenarios, along with the barriers that prevent, control or mitigate the scenarios (either preventive barrier or mitigating barrier). The barriers shall be further analysed for their defeat mechanism (called escalation factors) and corresponding measures provided to overcome the barrier defeat mechanism (called escalation factor controls). The MAH scenario shall encompass both process MAHs and other MAHs applicable to the facility. The process of creating a Bow Tie is most effectively accomplished using a Bow Tie workshop. It is important before the workshop to establish the scope and the context under which the bow ties will be developed.

Overview of BOW TIE :

The general focus of bow tie is managing Major Accident Hazards, as working personnel need to understand how these may occur and the barriers and escalation factor controls deployed to prevent them. Bow Tie diagrams shall be unit level / equipment specific MAH scenarios. A Bow Tie diagram shall be prepared for each MAH scenarios, presenting its causes, consequences and potential escalation scenarios, along with the barriers that prevent, detect, control or mitigate the scenarios (either preventative barrier or mitigating barrier). The barriers will be further analysed for their defeat mechanism (escalation factors) and measures provided to overcome the barrier defeat mechanism (escalation factor controls).

Key elements consider while developing the bow tie:

  • Hazard
  • Top event
  • Consequence
  • Threat
  • Barrier
  • Escalation Factor
  • Escalation Factor Control


The ‘hazard’ is an operation, activity, or material with the potential to cause harm. The hazard has the important function of defining the scope for the whole bow tie. Generic hazards can lead to generic bow ties and thus the hazard should be specific. This tends to add value because it increases the level of detail in the rest of the bow tie.

Formulating the Hazard would normally be identified in a PHA (Process Hazard Analysis) process (e.g., HAZID (Hazard Identification Study) or HAZOP (Hazard and Operability Studies))

Top Event

The top event is the moment when control over the hazard or its containment is lost, releasing its harmful potential. While the top event may have occurred, there may still be time for barriers to act to stop or mitigate the consequences. It is possible to identify multiple top events for one hazard – control can be lost over the hazard in different ways. Therefore, one hazard can result in multiple Bow Tie diagrams. For example, the hazard ‘working at height’ can result in two top events ‘dropped object’ and ‘person falls from height’. This will lead to two Bow Tie diagrams with different top events, but the same hazard.

Formulating the Top Event,

  • Describe how / what control is lost
  • Give an indication of scale if possible
  • The top event should not be a consequence
  • Choosing the best top event


Consequences are unwanted outcomes that could result from the top event and lead to damage or harm. For each top event there are multiple consequences placed on right side of the diagram, the ‘natural’ approach might be to define threats first. Generally, these would be major accident events, but lesser consequences can be selected if the aim is to map the full range of important safety and environmental barriers.

Formulation of consequence,

  • Consequences should be described as ‘[Damage] due to [Event]


Threats are potential reasons for loss of control of the hazard leading to the top event. For each top event there are normally multiple threats placed on the left side of the diagram, each representing a single scenario that could directly and independently lead to it.

Formulation of Threat

  • Threats should have a direct causation and should be specific.
  • Threats should be sufficient
  • Threats are not barrier failures


Barriers appear on the main pathways (threat to top event or top event to consequence). Barriers must have the capability on their own to prevent or mitigate a Bow Tie sequence and meet all the rule sets/validity requirements for a barrier to be effective, independent, and auditable. Barriers can be physical or non-physical measures to prevent or mitigate unwanted events.

Placement of barriers

  • Barriers should be placed in time sequence of their effect
S.NoItemAcceptance criteria
1.Preventive BarriersMinimum of 3 independent, effective and auditable barriers for each identified threat/cause line
2.Mitigative BarriersMinimum of 2 independent, effective and auditable barriers for each identified consequence
3.Escalation Factor Controls (EFC)Minimum of 2 Escalation Factor Controls (EFC) for each identified Escalation Factor

Prevention Barrier

A prevention or threat barrier (on the left side of the Bow Tie) is a barrier that prevents the top event from occurring. A key test for a prevention barrier is that it must be capable of completely stopping the top event on its own. This does not mean that it is reliable, only that in principle it can prevent or terminate a threat sequence (for example, an emergency shutdown valve can prevent a top event of ‘loss of containment’, but it can fail if the escalation factor control ‘partial/full stroke testing’ does not occur).There are two main ways in which a prevention barrier can have effect either to prevent the threat from occurring in the first place, or to stop an occurring threat from leading to the top event.

Mitigation Barrier

Mitigation barriers (on the right side of the Bow Tie) are deployed after the top event has occurred and should help to prevent the consequences from occurring or to mitigate the consequences and regain control once it has been lost. There are two main ways in which a mitigation barrier can have effect either to stop the consequence from occurring (ignition prevention), or to reduce the magnitude of the consequence (detection, ESD and emergency response).

 A mitigation barrier can have a lower performance than a prevention barrier in that it may only mitigate, not terminate, a consequence. As an example, a fire fighting system may reduce the impact of the fire but not eliminate it. Similarly, an ignition control barrier only reduces the likelihood of ignition but does not eliminate this potential.

Escalation Factor And Escalation Factor Control

An escalation factor can apply to barriers on either side of the Bow Tie diagram. For clarity of visual appearance, often they flow from the left on the prevention side, and from the right on the consequence side, but they are the same in all other respects. Controls along the escalation factor pathway are called escalation factor controls. The escalation factor is a condition that can reduce the effectiveness of the barrier to which it is attached. An escalation factor does not directly cause a top event or consequence, but since it degrades the main pathway barrier, the likelihood of reaching undesired consequences will be higher

Hazard & Operability Study (HAZOP):

Hazard and Operability (HAZOP) Study is a structured and systematic evaluation of a planned and/or existing operation to identify and evaluate potential hazards in design and operation. This study is carried out by a team of engineers from different disciplines.

The team looks at each section of a plant or system or operation (node), considers potential deviations from intended operation and analyses their consequences against any existing safeguards. Impact of identified hazards on safety, asset and environment are assessed.

HAZOP is a guideword driven brainstorming technique. Team members contribute based on their collective experience and lessons learnt from past projects. HAZOP study records the identified hazards without proposing any solution, unless a solution is obvious.Proposed solutions may include additional safeguards or operational procedures as necessary. The study record serves as a guide to determine the Health, Safety and Environment (HSE) issues to be resolved during the project.

Purpose of HAZOP:

HAZOP for any project or modification serves many purposes including

  • Identify the hazards inherent to the proposal.
  • Identify the credible equipment instrument failure likely to lead to accident scenarios / hazards / operability problems
  • In addition to these issues, Hazop occasionally identified items which could improve unit operations and efficiency


The HAZOP focuses on the process / utility system and associated interfaces. The basic concept of a HAZOP study is to take full description of the process and question every part of it during brain storming meetings attended by the different specialists involved in the process design to discover firstly what deviations from the intention of design can occur and what their causes and consequences may be.

The main steps involved in a HAZOP study are as follows:

  1. Select the node (Line, equipment or a system) on the P&ID;
  2. List of the intention & process parameters, guidewords for the nodes;
  3. List all deviations an ignore deviations that are not meaningful and apply the deviation;
  4. Brainstorm and list various causes of the deviation and ignore causes that are not credible;
  5. Determine the consequences of the deviations due to each listed credible cause;
  6. Identify safeguards already provided in the system
  7. Suggest recommendations / actions, should the safeguards be inadequate;
  8. Repeat steps 3 to 7 for each deviation
  9. Repeat steps from one (1) to eight (8) on the next node until all the nodes are covered.

Elements of HAZOP Study:

Node definition

The HAZOP study progresses through the plant node by node. The selection of the node sizes and the route through the plant is made before the study by the facilitator. The node should be described in terms of: -

  • Brief description of the node
  • Typical operating and design conditions
  • Method of operation and maintenance, and requirement for operator intervention


Flow, Pressure & temperature are usually regarded as the main parameters/elements. Additional parameters relate to general considerations like maintenance, safety, relief, corrosion/ erosion, instrumentation, start-up & shutdown, etc. Some of these may be selected for nodes in a study as appropriate based on relevance and concerns expressed by team members.


Guide words are simple words or phrases used to qualify or quantify the intention and associated parameters in order to suggest deviations.

Standard guide words; No/less, more/Less, As Well As/Part of, Reverse/Other Than, Early/Late, Before/After are applicable to each parameter. ‘Other Than’ is a very popular ‘catch all’ guide word at the end of each parameter


All credible/ possible scenarios leading to the deviations should be considered when determining causes. The Causes should be “Local” to the node being studied. The consequences are deliberated only after listing all the Causes. Two events happening simultaneously without any correlation should not be considered.


“Global” effects should be considered for the consequences i.e., keep researching the resulting reactions till you reach the Ultimate Consequence of a deviation.


Risk is a function of both Probability and Consequence. Safeguards reduce either Probability or Consequence.

These could be either related to hardware or operator practices & intervention., While selecting safeguards, you may consider engineering or administrative safeguards, but it is necessary to check whether these are existing & functional for the operating plant.



The purpose of the document is to identify hazardous conditions or high-risk situations and to evaluate concurrent activities along with production operations. SIMOPS are developed where work parties under different management structures carry out work, which results in hazards that may impact the other. e.g. construction and/or drilling in the same area.


SIMOPS matrices are constructed by group of technical personnel such as engineers of various discipline, and they are typically rooted in existing safety documents such as regulator-required HSE cases, HAZID report, HAZOP report safety “bow-tie” charts, procedural documents, and relevant safety standards.

The following aspects are analysed and recorded in the SIMOPS workshop:

  • Identify all construction, dismantling/demolition, pre-commissioning, commissioning and start up production operations, that may potentially be concurrently undertaken at the same time.
  • Identify if there is a potential hazard associated with the two operations occurring simultaneously.
  • Describe the normal safeguards required by the safety management systems that are applicable before any particular operation can be performed, e.g. PTW.
  • Identify possible restrictions (if any), which if in place, over and above the existing safety management systems, may enable the two independent operations to occur concurrently.
  • The proceedings of the SIMOPS shall be recorded in an agreed format. Typically, an Excel file is used by majority of the stakeholders.

The workshop team ranked each identified hazard according to the potential consequence and likelihood of occurrence with existing safeguards in place, HSE Risk Assessment Matrix. The likelihood and consequences of a hazard were mutually agreed (team consensus). Where information on complex hazards was not readily available, brainstorming, and open discussion were facilitated to ensure a collective/ common understanding of these hazards. The study team made recommendations for risk reduction where appropriate.

Essentially, the SIMOPS process flow chart is given below and further explained as follows:

  1. Identify “hazardous activities” for each relevant operation & fit to SIMOPS matrix
  2. Conduct a workshop involving multidisciplinary team and identify “permitted” or “prohibited” activities.
  3. Each matrix cell was allocated Y; N; R; N/A (for explanation, refer to Figure below).
  4. Based on this a list of Activities along with risk ranking control measures were captured.


The SIMOPS study applies a risk ranking matrix for assessing the risks associated to the activities in the SIMOPS MOPO. The risk ranking has been carried out in a qualitative manner based on the team experience of the consequence and the likelihood to each hazard scenario. Using a OQ HSE risk ranking matrix attached in Fig.1.6 OQ HSE Risk Matrix, each hazard is given a risk ranking with respect to impact on People, Asset, Environment and Reputation.

Constructability Review:


Constructability Review is systematic and structured multi-discipline workshop that is performed at EPC Stage of project lifecycle, to ensure that the facility is constructed safely and on time. The review shall assess "the ability to construct” from a construction (not design) viewpoint.

Constructability Review includes all aspects of construction work preparation, execution and completion that can make project safer and more cost effective to build, while maintaining quality, safety and access for personnel, tools and equipment during construction, and post- construction phase.

The main objectives of Constructability review are:

  • Ensure safety during the construction activities (Zero Accidents, incidents and injuries)
  • Reduce risks and uncertainties to the existing facilities by ensuring adequate preventive, control and mitigation barriers are in place (procedural and hardware)
  • Reduce conflicts / disputes
  • Improve project schedule
  • Reduce construction cost and enhance operability
  • Improve coordination between engineering, procurement and construction


The constructability review was undertaken using following steps:

  • Identification of construction activities for all disciplines location wise:
  • Identify Hazards due to “discipline-wise” construction activities undertaken and potential interactions with the existing operating facilities – this will be achieved by preparing a checklist comprising of sets of questions for each discipline scope;
  • Ensure adequate preventive, control and mitigation barriers are in place (procedural and hardware) while undertaking various activities;
  • Review action items from previous phase, if any;
  • Recommend additional measures required to ensure the construction activities can be undertaken safely; and
  • Identification of hazards from the existing facilities to the construction work.

Major Challenges, Difficulties, Issues And Concerns

For each of the criteria defined in the constructability worksheet, any major challenges, difficulties, issues or concerns identified that could have an impact on Constructability and the Project achieving its Objectives will be initially discussed by Review Team members in the Workshop.

Following discussion and agreement by the Review Team, any recommendations / actions identified based on each criterion subject to analysis were recorded in the Constructability Worksheet including action parties responsible for action closure.

Recommended Action To Be Considered

If there were no current resources or no data / knowledge available about the specified criteria used in the analysis, a recommendation will be made based on Team consensus to address the concerns / issues relating to the criteria specified. In addition, where the Review Team thought appropriate, additional criteria was added to the Constructability Check List specific to this Project and included in the analysis.



Valves are rated by criticality to help ensure that critical valves are located to provide for rapid and effective identification and operation. The following three categories are recommended. Risks to health and safety, including risk of human error, shall be kept ALARP.

Category-1 (C-1) Critical Valves

Valves include those essential to normal or emergency operations where rapid and unencumbered access is essential. The height, reach distances and visibility shall conform to the “preferred” location as outlined in the following sections.

These are valves that meet any or all of the following criteria:

  1. Valves essential to production.
  2. Valves essential to process safety or asset integrity
  3. Particularly large valves
  4. MOVs with high failure rates and which require rapid corrective action.
  5. Valves being used in a service or under operating conditions where the failure rates are not known or may be unreliable.
  6. Valves where consequence of failure to obtain quick access would be serious (e.g. process shutdown and/or damage to facilities or personnel).
  7. Valves for which the expected routine operation, inspection and/or maintenance is more frequent than once every 6 months.

Access Requirement for C-1 Valves

Permanent accessibility shall be provided via a permanent standing elevated surface. If such access at ground or deck level is not practical, access by stairs to the elevated platform is acceptable.Valve identification and status shall be clearly visible to an approachable operator position i.e., on an adjacent walkway, access platform, or in space around equipment that is intended for human access.

Category-2 (C-2) Non-Critical Valves

Valves are those that are not critical for normal or emergency operations but are used during routine inspection or maintenance activities.

These are valves that meet any or all of the following criteria:

  1. Valves associated with equipment for which rapid intervention is unlikely to be needed.
  2. Valves with a low operating or inspection frequency (i.e., less than once every 6 months).

Access Requirement for C-2 Valves

Height & reach distance and visibility of C-2 valves should be the same as for C-1 valves i.e., “preferred” location as outlined in the below figures. C-2 valves may be located within the “acceptable area” as outlined in the below Figure, depending on their size and the force needed to operate them. Where ground level access is not justifiable, a vertical fixed ladder plus a small standing surface shall be provided for access to C-2 valves.

The use of auxiliary equipment to gain access (e.g., mobile platforms, man lift, or scaffolding) for maintenance purposes may be acceptable as long as it is indicated and allowed for in the design by preserving sufficient space and access for personnel, tools, parts, and equipment.

Identifying and inspecting the status of C-2 valves may require the operator to enter space not intended for human access, or to temporarily adopt an awkward posture provided doing so does not induce human error or put the operator at risk of injury or exposure to hazards.

Category-3 (C-3) Non-operational Valves

Valves are normally non-operating valves that are used or inspected in particular circumstances on an infrequent or rare basis (e.g., hot tap valves, hydrostatic test vent, high point vent or low point drain valves located in pipe rack) and are not used in HSSE critical activities.

Access Requirement for C-3 Valves

Permanent accessibility to and visibility of C-3 valves is desirable but not essential. No specific location requirements are imposed.The use of auxiliary equipment to gain access (e.g., mobile platforms, personnel lift, and/or scaffolding) to C-3 valves shall be indicated and allowed for in the design.Portable ladders should not be used for accessing C-3 valves. Any proposed exception(s) to this shall be subject to specific review and approval.Height and reach distances to C-3 valves when operated from auxiliary equipment shall conform to the “preferred” location as outlined in the below figures.


  1. Distances or heights are measured to hand-wheel centreline. For gear-operated valves with a handwheel provided with a spinner handle, maximum horizontal distance is measured to the edge of the hand-wheel furthest from the operator.
  2. Heights are to be to the maximum extension of valve stem for rising stem valves.
  3. These dimensions are appropriate male and female personnel worldwide from 5th to 95th percentile, except that the top limit for the “Preferred” choice location should be reduced by 100mm (4 in) to accommodate male and female populations in regions such as West Africa, Southeast Asia, and Southern China, parts of Latin America, India and Japan.
  4. For valves located below 455 mm (18 in), sufficient clearance of at least 910 mm (36 in.) should be provided behind the operator to accommodate a squatting posture.


  1. Distances or heights are measured to hand-wheel centreline. For gear-operated valves with a handwheel provided with a spinner handle, maximum horizontal distance is measured to the edge of the hand-wheel furthest from the operator.
  2. These dimensions are appropriate for personnel worldwide, from the 5th percentile of the female population to the 95th percentile of the male population, except that the top limit should be set at 1755 mm (69 in) for the 5th percentile males and 66 in (1675 mm) for 5th percentile females in regions such as West Africa, Southeast Asia, Southern China, Parts of Latin America, India and Japan.
  3. For valves located below 455 mm (18 in), sufficient clearance of at least 910 mm (36 in.) should be provided behind the operator to accommodate a squatting posture.

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