SIL Assessment & Verification EPIC for Utilization of Produced Water and Effluent Water Treatment at Qatar Energy

Industrial oil and gas facility with multiple large storage tanks in the foreground and refinery structures with smokestacks in the background against a clear blue sky
Oil and gas facility showcasing storage tanks and refinery infrastructure for the SIL Assessment & Verification EPIC for Utilization of Produced Water and Effluent Water Treatment at Qatar Energy

Introduction:

iFluids Engineering & Consultancy W.L.L. was awarded the task of conducting the SIL Assessment & Verification study for the EPIC (Engineering, Procurement, Installation, and Commissioning) scope of two critical projects for Qatar Energy:

  1. SIL Assessment & Verification for the Utilization of Produced Water from Storage
  2. SIL Assessment for the New Effluent Water Treatment Plant (NEWTP) for NGL at Mesaieed

These studies aim to ensure that Safety Instrumented Systems (SIS) are adequately designed to meet the necessary Safety Integrity Levels (SIL) for preventing undesired events, ensuring safe operations, and complying with regulatory requirements.

What is a SIL Study?

A Safety Integrity Level (SIL) study is used to assess and determine the required safety integrity levels for Safety Instrumented Functions (SIFs). SIL indicates the level of risk reduction needed to protect against hazardous events. A LOPA (Layers of Protection Analysis) methodology is typically used in these assessments to evaluate and assign SIL ratings to various safety functions and protective layers in a system.

Case Study 1: SIL Assessment for Produced Water Utilization from Storage Tanks

Objective:

This study was conducted to evaluate the safety systems involved in produced water utilization from Crude Oil Storage Tanks (COST) at three degassing stations:

  • Khatiyah Main Degassing Station (KMDS)
  • Fahahil Main Degassing Station (FMDS)
  • Jaleha Degassing Station (JDS)

The produced water, which is a byproduct of crude oil separation, was previously disposed of into disposal wells. However, Qatar Energy aims to reuse this water for water injection (PWI) into reservoirs, reducing environmental impact and conserving groundwater resources.

Key Facilities Involved:

  • KMDS, FMDS, JDS: These stations handle oil and gas production from multiple reservoirs, such as Arab C, Arab D, and Uwainat.
  • Produced Water Treatment: Water is extracted and treated to be re-injected into reservoirs as part of enhanced oil recovery (EOR) efforts.

Planned Modifications:

  • PW Collection Tank: A new system will collect produced water from COSTs, which will then be routed to the Produced Water Secondary Treatment (PWST) unit.
  • Secondary Treatment (PWST): This unit will further treat the water for re-injection, replacing the previous disposal into aquifer wells.

SIL Study Approach:

The LOPA methodology was used to:

  • Identify potential hazards and safety functions.
  • Assess the required SIL levels for each function based on the potential risk.
  • Validate that all Safety Instrumented Functions (SIFs) provide the necessary level of risk reduction to mitigate identified hazards.

Case Study 2: SIL Assessment for New Effluent Water Treatment Plant at NGL, Mesaieed

Objective:

The study focused on the Effluent Water Treatment Plant (NEWTP) for the NGL Complex in Mesaieed. This facility will treat process wastewater and surface runoff to meet irrigation water quality standards, as per MME (Ministry of Municipality and Environment) regulations.

Currently, there is no wastewater treatment at the NGL complex, and treated effluent is discharged into the marine environment. The new treatment facility will ensure compliance with MME guidelines, reusing treated effluent for irrigation and landscaping purposes at the NGL facility.

Project Features:

  • Effluent Collection & Transfer Systems: Efficient systems to collect, transfer, and treat wastewater from NGL facilities.
  • Irrigation & Landscaping Reuse: The treated water will be repurposed for irrigation within the NGL facilities, reducing the consumption of freshwater.
  • MME Compliance: The treatment plant ensures wastewater meets the irrigation water quality standards outlined in Qatar’s Consent to Operate (CTO) and Environmental Guidelines.

SIL Study Approach:

The LOPA methodology was used for:

  • Identifying hazardous scenarios related to effluent water treatment.
  • Quantifying risk reduction requirements and assigning appropriate SIL levels for each SIF.
  • Evaluating the SIS components, including their failure probabilities and their ability to meet safety standards.

SIL Assessment Process:

The following process was followed for conducting the SIL Assessment:

  1. Hazard Identification: Potential hazardous events were identified using HAZOP (Hazard and Operability Study).
  2. Risk Quantification: Each hazard scenario was analyzed to determine the Required Risk Reduction (RRR).
  3. LOPA Analysis:
    • Initiating Events were identified, and their frequencies were quantified.
    • The Independent Protection Layers (IPLs) were reviewed to determine their effectiveness in mitigating the identified risks.
  4. SIL Classification: SIL levels were assigned to the identified Safety Instrumented Functions (SIFs) based on the calculated risk reduction.
  5. SIL Verification:
    • The PFDavg of each SIF component (sensors, logic solvers, actuators) was verified to ensure compliance with the required SIL levels.
    • Failure Rate Analysis was performed to confirm the reliability of each SIS component.
Flowchart illustrating the process of Safety Lifecycle Structure and Planning, divided into three main phases: Analysis, Implementation, and Operation. The Analysis phase includes Hazard and Risk Assessment, Allocation of Safety Functions to Protection Layers, and Safety Requirements Specifications for the Safety Instrumented System (SIS). The Implementation phase covers Design and Engineering of the Safety Instrumented System, Design and Development of other Means of Risk Reduction, and Installation, Commissioning, and Validation. The Operation phase involves Operation and Maintenance, Modification, and Decommissioning. The flowchart is bordered by sections for Management of Functional Safety and Functional Safety Assessment and Auditing, and includes Verification.
Safety Lifecycle Structure and Planning across Analysis, Implementation, and Operation stages

SIL Verification Details:

The SIL Verification study focused on validating the design and integrity of the Safety Instrumented Systems, ensuring that they meet the required SIL ratings for effective risk reduction:

  • Failure Rate Data: Data from each SIS component (sensor, logic solver, actuator) were used to estimate failure rates, using Failure in Time (FIT) values.
  • PFD Calculation: The Probability of Failure on Demand (PFDavg) was calculated for each SIS loop, based on component failure rates.
  • System Architecture Review: The architecture of the SIS loop was assessed to ensure that it met the necessary SIL ratings.

Verification Assumptions:

  • Failure rates are assumed constant over the component’s usable life.
  • Proof Tests are assumed to be 100% effective in detecting faults.

A Mean Time to Repair (MTTR) of 24 hours was assumed for restoration of system components.

SIL Study Results:

  • The SIL ratings for all identified SIF loops were found to meet or exceed the required SIL levels for safety, environmental protection, and operational reliability.
  • The PFDavg values for each system were calculated and verified to ensure that the Safety Instrumented Systems (SIS) met the targeted SIL.

The SIL verification study confirmed that the SIS components, including sensors, logic solvers, and actuators, are properly selected and configured to meet the required safety integrity levels.

Conclusion:

The SIL Assessment & Verification studies for Qatar Energy’s projects—Produced Water Utilization and Effluent Water Treatment—have successfully validated the safety integrity of the systems in place. These studies ensure that Qatar Energy’s facilities are compliant with regulatory safety standards and that the risk of hazardous events is minimized to acceptable levels.

The use of LOPA methodology and the detailed SIL verification process provides assurance that the projects will operate safely, protect the environment, and contribute to sustainable water management practices. The overall safety systems are designed to meet Qatar Energy’s ALARP (As Low As Reasonably Practicable) standards, ensuring that the systems are reliable and fit for purpose.