SIL Assessment & Verification EPIC for Utilization Of Produced Water From Storage & New effluent Water Treatment Plant of Qatar Energy.

Qatar Energy -Oil & Gas

iFluids Engineering and Consultancy WLL was awarded to perform SIL Assessment & Verification study for EPIC various facilities of Qatar Energy, including:

  • SIL Assessment & Verification – EPIC For Utilization Of Produced Water From Storage
  • SIL Assessment for EPIC of new effluent water treatment plant for NGL at Mesaieed

What is SIL Study?

A Safety Integrity Level (SIL) Study is essential for evaluating the specific level needed to define the safety integrity requirements of security instrumented functions (SIF) to be assigned to security instrumented systems. To know more Click Here

Case Study 1 – SIL Assessment & Verification – EPIC For Utilization Of Produced Water From Storage

The SIL Assessment & Verification study for the EPIC scope of utilizing produced water from storage tanks at degassing stations for PWI of  Khatiyah Main Degassing Station (KMDS), Fahahil Main Degassing Station (FMDS), and Jaleha Degassing Station (JDS) was conducted by iFluids Engineering & Consultancy W.L.L.

The SIL Study is commonly conducted in order to validate that the Safety Instrumented Functions (SIFs) identified through a Layers of Protection Analysis (LOPA) conform to their intended SIL level.

Qatar Energy, the state-owned entity responsible for Qatar’s oil and gas production, processing, and exportation, manages fields both onshore and offshore. The onshore Dukhan Field, located approximately 80 km west of Doha, stretches about 65 km long and 5-12 km wide. It encompasses various production zones, including Gas Recycling Plant-Arab D, Khatiyah, Dukhan Township, Fahahil, Jaleha, and Diyab, housing a network of oil, gas, and water injection wells.

Key facilities within Dukhan include Khatiyah Main Degassing Station (KMDS), Fahahil Main Degassing Station (FMDS), and Jaleha Degassing Station (JDS). These stations play vital roles in crude oil processing and storage. Stabilized crude oil from KMDS, FMDS, and JDS is treated, settled, and stored in Crude Oil Storage Tanks (COST) before being transported to Mesaieed via a pipeline connected to Um Bab. Currently, the produced water from these COSTs is disposed of into wells linked to the Umm-Er Dhuma aquifer.

To protect the groundwater environment, QatarEnergy plans to recover and reuse the produced water from these COSTs. The recovered water will be collected in an underground tank and then routed to a new Produced Water Secondary Treatment (PWST) unit for further processing, with the intention of utilizing it as injection water.

Each of the degassing stations serves specific oil reservoirs:

  • KMDS processes well fluids from Arab C, Arab D, and Uwainat oil reservoirs.
  • FMDS, situated at the heart of the Dukhan Fields, receives well fluids from Arab C and Arab D fields, along with partially degassed crude from Fahahil South and Fahahil North.
  • JDS, located approximately 35 km from Dukhan, handles well fluids from production wells in the Arab C and Arab D reservoirs, some of which are piped in via the Diyab manifold.

The well fluids undergo four stages of separation, resulting in three distinct phases:

  • Degassed crude oil.
  • Rich associated gas (RAG).
  • Produced water.

The degassed crude oil is stabilized, stored in COST, and subsequently pumped to the Umm Bab Booster Station for transport to Mesaieed. At COST, the crude is treated for dewatering and desalting. The RAG is dehydrated and can either be used for gas lift or sent to the Field Support Platform (FSP) for further processing.

The produced water from the separation process is directed through a water treatment unit, including hydro-cyclones and a degasser, before being transferred to the Produced Water Injection (PWI) system using PW transfer pumps. In the unlikely event of PWI system unavailability, there is an alternate route to dispose of the produced water into disposal wells.

Under the DPFU project, a new PWST is planned. This project primarily involves modifications to collect produced water drained from the COSTs into a new PW Collection Tank, which will then be routed to the PW Secondary Treatment section for degassing. This approach replaces the current practice of disposing of produced water into disposal wells in the aquifer.

Case Study Part 2 – SIL Study EPIC of new effluent water treatment plant for NGL at Mesaieed

The primary objective of this SIL study was to assess the hazards and impacts of the proposed project on health, safety, environment and the company’s reputation and assign SIL Rating for each SIF associated with this project. The LOPA worksheets containing the cause, consequence, protection layers have been generated and Target SIL Rating & Target RRF for each of the SIF were determined at the end of the workshop.

Middle East Projects International (hereafter referred as Technip Energies), an Internationally reputed Engineering Organization operating globally in Oil & Gas and Petrochemical sectors which is professionally qualified and has experience in Detailed Engineering Services, has been awarded by EPIC contractor Medgulf Construction, to perform Detailed Engineering (DE) for the Project “EPIC for New Effluent Water Treatment Plant for NGL at Mesaieed” for Qatar Energy.

Natural Gas Liquid (NGL) Complex at Mesaieed Industrial City (MIC) generates process and surface run-off effluent wastewater. Currently, there are no wastewater treatment facilities in NGL Plants.

As per the Ministry of Municipality and Environment (MME) requirements, industries are prohibited to discharge their treated industrial and process wastewater from existing facilities to the marine coastal environment. Instead, the wastewater shall be further treated to meet the irrigation water quality standards mentioned in the “Consent to operate” (CTO), and the treated water shall be reused for irrigation and landscaping of NGL facilities.

To meet the MME requirements, a New Effluent Water Treatment Plant, referred hereafter as “NEWTP,” has been proposed to treat the effluents generated from NGL Plants to meet the irrigation water quality.

Front End Engineering Design (FEED) was completed by another contractor covering the following:

  • Identification of the effluent sources.
  • Provision of suitable collection and transfer systems at NGL areas.
  • New effluent treatment facility to treat the effluents to meet irrigation water quality.

The objective of this project is to provide an Effluent Water Treatment Plant for NGL Complex, including collection, transfer systems, re-use of the treated water for irrigation to meet MME requirements and Consent to Operate (CTO) and KAHRAMAA water supply to boiler blowdown quench in order to avoid from high TDS in effluent water.

SIL Assessment

SIL Assessment is a defined process of hazard analysis of identified hazard(s) for the purpose of determining the SIL required of the SIF(s) which are required to protect against the hazard(s).

The intent of the SIL Assessment study is to assess the safety integrity requirements on the Safety Instrumented Functions (SIF) to be allocated to the Safety Instrumented Systems (SIS). The SIL assessment determines the risk reduction required of the SIF such that it provides sufficient protection layer or safeguard to meet the required risk reduction for a hazard. Quantification of the risk reduction requirements is given in terms of a Safety Integrity Level (SIL) requirement.

The risk reduction is calculated as the gap between the existing risk posed by the process or equipment and the risk target. Risk reduction is provided by process and mechanical integrity, independent protection layers and if so required SIS. It also answers the following questions:

  • What is the likelihood of an undesired event?
  • What is the risk associated with the event?
  • Are there sufficient risk control measures (or “layers of protection”)?

The study on SIL classification has been carried out utilising the LOPA methodology in order to allocate SIL levels to the Safety Instrumented Systems. The SIL classification study is a methodology used to determine the appropriate design of safety measures, including instrumentation, that effectively mitigate process hazards in terms of safety, environmental consequences, and economic losses.

It comprises a semi-quantitative assessment of the process equipment and systems to be protected by the Safety Instrumented system, to identify potential hazards and to assess the risk. This assessment is developed on the basis that, initially, no protective systems are in place, so that a basic level of risk can be established for the equipment under control.

The SIL derived rating is a quantification of the level of risk mitigation necessary for the Safety Instrumented System to ensure that the remaining risk is deemed acceptable or ALARP (As Low As Reasonably Practicable). The SIL rating covers the complete loop and is used in the specification of the Safety Instrumented System, e.g., from initiating devices through the logic solvers and controllers to the final actuating elements, in order that the system will adequately meet the design intent. The SIL classification study has been conducted as a team based brainstorming workshop led by the chairman with proceedings recorded by a dedicated scribe.

The following documents/ drawings were referred during the SIL workshop.

  • P&IDs used for HAZOP Workshop.
  • Cause and Effect diagram.

The preparative work consists of four stages: training / briefing to team members, obtaining the necessary data; converting the data to a suitable form, planning the study sequence and arranging the meetings. The LOPA methodology uses order of magnitude categories for initiating event frequency, consequence severity, and the likelihood of failure of IPLs to approximate a risk level for any hazardous scenario.

The steps used to conduct the LOPA are listed below:

  • Step 1: Select Hazard Scenario from HAZOP based on its severity level.
  • Step 2: Select Target Mitigated Event Frequency (TMEF).
  • Step 3: Identify cause(s) from the HAZOP and quantify Initiating Event Frequency.
  • Step 4: Determine Intermittent Hazard(s) credit if applicable.
  • Step 5: Identify Independent Protection Layers (IPLs) from HAZOP safeguards.
  • Step 6: Quantify the Probability of Failure on Demand (PA) for each IPL.
  • Step 7: Identify and quantify Conditional Modifiers / Vulnerability Factors if applicable.
  • Step 8: Calculate the LOPA Ratio for each Safety, Environment and Asset Consequence Category as applicable. Using the LOPA Ratio, determine Integrity Level requirements for the existing Safety Instrumented System (SIS) (if required), or identify requirements for additional IPL or SIS and evaluate SIS integrity level.

Where protection is provided by SIS, or a SIS is recommended, the LOPA determines the Safety Integrity Level (SIL).

The LOPA ratio for Safety, Environment, Asset and Reputation Integrity Levels were used to determine the required Integrity Level and PFD of each SIS. The highest of the four integrity levels were used as the design basis for that SIS. The IL of the SIS is the highest integrity level for which the SIS provides protection. For example, different ILs may be calculated for each separate Cause- Consequence pair for which the SIS acts as protection. The PFD of the SIS is required to be less than or equal to the LOPA ratio for all Safety, Environment, Asset, Reputation Integrity Levels for which the SIS provides protection. The risk reduction requirement for each IL rating were derived from Qatar Energy Standard to conduct SIL study and is tabulated below. The PFD of the overall safety provisions must meet these values, regardless of the method used.

SIL Verification

The individual certification of the subcomponents comprising the Safety Instrumented System (SIS) loop has been conducted to assess their compatibility with the Safety Integrity Level (SIL). The primary aim of the verification study is to determine the average Probability of Dangerous Failure (PFDavg) and the architectural limitations that govern the attainable Safety Integrity Level (SIL) rating for the Safety Instrumented System (SIS) loop.

The SIL Verification study has been conducted for the specified configuration. Based on the Failure Rate Data provided for the individual components, the quantitative analysis of the sub-components for the identified SIF loops have been performed. This analysis has revealed the overall SIL Rating for the Safety Instrumented System.

This report focuses on the validation of SIF loops through the careful selection of components and configuration. The calculations of the failure rate for the system took into account the following assumptions.

  • Failure rates are assumed to be constant during the usable life of the sub-components (Break–in period failures or end of life scenarios are not taken into account).
  • Proof Tests are assumed to detect all of the faults in the system
  • The calculation of PF Davg involves utilising a minimum proof test period that exceeds 50% of the demand of the subsystem.
  • All components have been identified to be operating under Low Demand mode
  • The total number of operational hours in a single year is assumed as 8760 hours.
  • The mean time to repair/ restoration (MTTR) for each component was assumed as 24 hours.
  • Restoration is assumed to be 100% effective to restore each component to fault-less state.
  • Non-interfering components, i.e. those components which do not impact the performance of the safety function of the system (Interaction-Free modules), are not included in the verification calculations.

The approach followed for the verification of the SIL rating of the identified SIF loops are given below:

  • Estimation of the PFDavg for the individual sub-systems (Initiating Device; Logic solver; Final Element).
  • The allocation of SIL compatibility ratings to the assembly based on their respective configurations.
  • Selection of proof test interval to obtain the least PFD

The values of Failure rate in Time (FIT) used in the calculations were collated either from the certificates issued or from the failure rate data shared by the client for the individual components. In compliance with applicable portion, the calculations were carried out for each design configuration within the specified assembly.

The current report contains the results of the verification of the SIL class of the identified SIF loops of KMDS as per IEC requirements for subsystem. Achieved SIL rating/ RRF is higher than Targeted SIL rating/ RRF, so the current SIL rated SIF loops have met the requirement.