SPE/IADC-173117-MS Experiences, Challenges, and Common Recommendations from Performing HAZOP Studies to Identify Potential Hazards Associated to Surface Gas and Mud Handling Systems During Drilling Operations Carolina Rubiano, Paul Sullivan, Frederic Gil, and Jordon Tench, BP
Copyright 2015, SPE/IADC Drilling Conference and Exhibition This paper was prepared for presentation at the SPE/IADC Drilling Conference and Exhibition held in London, United Kingdom, 17–19 March 2015. This paper was selected for presentation by an SPE/IADC program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers or the International Association of Drilling Contractors and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers or the International Association of Drilling Contractors, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers or the International Association of Drilling Contractors is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE/IADC copyright.
Abstract This paper summarizes a number of the challenges encountered and the common findings in HAZard and OPerability (HAZOP) studies related to the surface gas and mud handling systems on drillships, jackups, semi-submersibles, and land rigs. These HAZOP studies are conducted by experienced multi-disciplined teams that combine the operations, engineering, and process safety personnel from both the oil company and the drilling contractor.
Introduction During the rig intake process, HAZOP studies are used to review the surface gas and mud handling systems for a number of operational modes. These operational modes include: drilling, well control, negative pressure test and cementing and pressure testing. If potential design and operational deficiencies are identified (e.g., related to events which would require handling gas at surface following a well influx) recommendations are suggested to further reduce the risk to both the drilling contractor and the operator.
HAZOP Technique What are HAZOPs? The HAZOP technique is a well known industry risk assessment technique. It is a rigorous and systematic risk identification tool used by a multidiscipline team to assess the potential design and operational deficiencies of facilities. The HAZOP methodology uses a series of guidewords to examine potential deviations from normal operating conditions. The deviations are then examined to identify potential hazards to people, environment, assets, company financial standing, reputation, and/or license to operate. These hazards are then eliminated or mitigated to reduce risk [7, 8, 12, 13, 14, 17, 18]. HAZOP studies also provide an excellent vehicle to identify opportunities for improvement to operating procedures, application of inherently safer design principles, and human factors considerations [9]. The HAZOP process, (Figure 1), seeks to:
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Document the design intent and operating conditions for the process section (known as ‘node’) under discussion. This includes documenting how a component or system is expected to operate and the purpose of the system, see Table 1.
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Table 1—Nodes Commonly Used for Surface Gas and Mud Handling HAZOPs
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Table 1 (Continued)—Nodes Commonly Used for Surface Gas and Mud Handling HAZOPs
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Figure 1—HAZOP Process
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Identify the potential causes and consequences of credible worst case hazards in a systematic and comprehensive manner. Typical questions include: What can go wrong? What are the potential effects and severity? ● Identify and evaluate the existing mitigation measures (safeguards or barriers) and their effectiveness for each scenario (these include engineered systems and procedural or administrative controls associated with hazard prevention, detection, control, mitigation, and response). ● Assess the risk presented by the identified potential hazard scenario by addressing the severity of the worst credible consequence and the likelihood of the hazardous event (including a reasonable evaluation of the effectiveness of the existing safeguards). ● Recommend additional possible mitigation or control measures for consideration to improve the safety of the facility. Note: With respect to the surface gas and mud handling system HAZOP studies, the severity is determined by assessment of the worst credible consequence while excluding the intended mitigation of
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the safeguards (i.e., assumes that all safeguards fail). The term “credible” means what is physically possible, not whether such consequences have ever occurred or might occur. Make-up of the HAZOP Team The HAZOP technique relies on a team whose membership includes a broad range of knowledge and experience in design and operation of the system(s). A successful surface gas and mud handling system HAZOP study is conducted by a multi-disciplinary team with knowledge of the rig’s equipment, functionality, well characteristics, drilling programme, operations, and potential failure modes. The HAZOP team typically consists of: ● ● ● ● ● ● ● ● ● ●
Facilitator and Study Leader Scribe Rig Supervisor or Comapanyman Drilling Superintendent Drilling or Completion Engineer Process Safety Engineer Driller or Assistant Driller Toolpusher Offshore Installation Manager Rig Manager
Other technical specialists (e.g. cementing or equipment manufacturer representatives) can also supplement the core team described above. This broad participation in the surface gas and mud handling system HAZOP typically also enhances participant’s knowledge and understanding of the equipment and systems under review. Information Essential for an Effective HAZOP The availability of up-to-date Process Safety Information (PSI) is essential for an efficient and accurate HAZOP [7, 18, and 19]. This means that the changes that have occurred at the facility have been captured and are reflected in the information and drawings. Important information to include in a HAZOP is a set of up-to-date Process and Instrumentation Diagrams (P&IDs) [7, 19]. The typical PSI used in support of surface gas and mud handling system HAZOP studies includes: ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
General Arrangements (layout drawings) Surface gas and mud handling system P&IDs Hazardous area classification drawings Diverter operation and interlock details (if Diverter exists) Previous process hazard analysis (PHA) or HAZOP reports Alarm and trip settings for any instrumented device (e.g., Pit volume totalizer, Fire and gas detection system, etc.) Typical reservoir fluid composition, pressure, temperature, and estimated flow Material Safety Data Sheets (MSDS) Details of gas detection on drill floor, shaker house, and pit areas Emergency shutdown (ESD) system functions Operations manuals and procedures Well control procedures Emergency response procedures Details of deluge provided on and in the vicinity of the surface gas and mud handling equipment and systems Dispersion and thermal radiation studies for associated vents and diverters (if diverter exists)
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Information on neighboring occupied areas (e.g., distance to populated areas, type of neighboring facilities [onshore rigs only]) Typical personnel distribution on the rig Inspection and testing results, maintenance records, operational history, and current condition of equipment to be reviewed during HAZOP Maintenance procedures Design basis for vessel sizing, venting, and operating limits for system components (Mud Gas Separator, PSV, burst disk, etc.) Pump curves and data sheets Safety philosophy documentation Safety case Safety critical equipment list Well control bridging document between drilling contractor and operator Aerial photography of the site and surrounding area (onshore rigs only).
Note that inaccurate and out-of-date P&IDs can be a common issue to be addressed prior to the execution of the HAZOP study. Scope of the Surface Gas and Mud Handling System HAZOP Study The surface gas and mud handling systems are divided into sections, called nodes, to allow the HAZOP team go through the process in a systematic way one node at a time. Nodes are specific to individual drilling programmes. The nodes commonly used in the surface gas and mud handling HAZOPs are described in Table 1. Selection of Guidewords and Deviations Guidewords are combined with process parameters (see Table 2) to create deviations from the design intent and initiate a brainstorming exercise. The brainstorming exercise is used to identify potential causes that could generate the deviation. If a cause is identified that has the potential to generate a process parameter deviation, then the associated scenario is developed, the risk is assessed, the safeguards are identified, and risk reduction opportunities are evaluated.
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Table 2—Common guidewords used in the Surface Gas and Mud Handling system HAZOP studies
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Table 3—Common findings and recommendations in surface gas and mud handling system HAZOP studies (Note: these are not ranked by importance)
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Table 3 (Continued)—Common findings and recommendations in surface gas and mud handling system HAZOP studies (Note: these are not ranked by importance)
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Table 3 (Continued)—Common findings and recommendations in surface gas and mud handling system HAZOP studies (Note: these are not ranked by importance)
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Table 3 (Continued)—Common findings and recommendations in surface gas and mud handling system HAZOP studies (Note: these are not ranked by importance)
Some common guidewords are: ‘more’, ‘less’, ‘no’, ‘reverse’, and ‘other than’ [7, 14, 17, 19]. The deviations typically used for surface gas and mud handling system HAZOP studies are described in Table 2.
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Common findings and recommendations This section summarises common findings and recommendations in HAZOP studies conducted on rig surface gas and mud handling systems. These studies may include systems on drillships, jackups, semi-submersibles, and land rigs. Recommendations typically are made when a team considers that: ●
Engineered systems and procedures or administrative controls are unlikely to sufficiently mitigate a risk. ● An operability concern is identified that requires intervention or attention. ● A non-compliance with a regulation or an industry standard (e.g., API Spec 53) is identified.
Conclusions A consistent approach is required for the assessment and management of risks and to enable drilling contractors and operators to consistently apply risk management to effectively integrate HSE into their operations [12, 13]. The application of the HAZOP methodology to review the surface gas and mud handling systems on drilling rigs has permitted operators and drilling companies, by working together, to systematically identify and mitigate risks by assessing potential design and operational deficiencies before the rig starts operation, in a mutually beneficial process. A number of recommendations were suggested as means to further reduce the risk to both the drilling contractor and the operator. These recommendations and learnings have been collected and evaluated to identify common themes that have been shared across regions and drilling contractors. Common recommendations have included: ● ● ● ● ● ● ●
Conduct specialized risk assessments to further understand risks (e.g., gas dispersion study for hydrocarbon vents) Modify systems to help prevent or reduce the likelihood of undesirable consequences (e.g., validate philosophy for using common vent lines) Conduct design verifications to better assure equipment and/or systems operate within design limits (e.g., pressure safety valve (PSV) discharge capability calculations) Update procedures and training to enhance well control response (guidance on upset conditions; e.g., choke blockage/wash-out and diverter upset conditions) Provide additional instrumentation to increase the available response time for a driller to detect and react to an undesired scenario (e.g., health/degradation of MGS liquid leg) Enhance inspection and preventative maintenance requirements for a number of critical equipment/systems (e.g., MGS vents and instrumentation) Update process safety information including process and instrumentation diagrams (P&IDs) (especially important for managing changes to rig systems)
HAZOP studies have also: 1. Enhanced personnel knowledge and understanding of the surface gas and mud handling process and equipment or systems. 2. Promoted workforce participation. 3. Provided a vehicle to improve emergency response plans and drill programs. 4. Facilitated the verification of PSI status. 5. Facilitated the proactive verification that equipment and systems meet design and operational requirements.
References 1. API. Guide for Pressure-Relieving and Depressuring Systems, API Std 521, Fifth Edition, American Petroleum Institute, Washington DC, January 2007.
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2. API. Blowout Prevention Equipment Systems for Drilling Wells, API Std 53, Fourth Edition, American Petroleum Institute, Washington DC, November 2012. 3. API. Recommended Practice for Development of a Safety and Environmental Management Program for Offshore Operations, API Recommended Practice 75, Third Edition, American Petroleum Institute, Washington DC, May 2008. 4. API. Specifications for Choke and Kill Systems, API Specification 16C, First Edition, American Petroleum Institute, Washington DC, July 2010. 5. API. Specifications for Control Systems for Drilling Well Control Equipment and Control Systems for Diverter Equipment, API Specification 16D, Second Edition, American Petroleum Institute, Washington DC, August 2013. 6. API. Venting Atmospheric and Low- Pressure Storage Tanks, API Std 200, Seventh Edition, American Petroleum Institute, Washington DC, March 2014 7. CCPS. Guidelines for Hazard Evaluation Procedures, 3rd Edition, Center for Chemical Process Safety (CCPS) of the American Institute of Chemical Engineers (AIChE), New York, New York, 2008. 8. CCPS. Center for Chemical Process Safety. Inherently Safer Chemical Processes - A Life Cycle Approach (2nd Edition). Center for Chemical Process Safety (CCPS) of the American Institute of Chemical Engineers (AIChE), New York, New York. 2009. 9. DNV. Safety Principles and Arrangements. Offshore Standard DNV-OS-A101. Det Norske Veritas. April 2011. 10. DNV. Drilling Plant. Offshore Standard DNV-OS-E101. Det Norske Veritas. October 2009. 11. G.R. MacDougall. Mud/Gas Separator Sizing and Evaluation. SPE Drilling Engineering, December 1991 12. IADC. Health, Safety and Environmental Case Guidelines for Mobile Offshore Drilling Units, Version 3.5, International Association of Drilling Contractors, Houston, Texas, January 2014. 13. IADC. Health, Safety and Environmental Case Guidelines for Land Drilling Units, Version 1.0.1, International Association of Drilling Contractors, Houston, Texas, July 2009. 14. IEC. Hazard and operability studies (HAZOP studies) – Application guide, International Standard IEC 61882:2001, First edition, International Electrotechnical Commission (IEC), Geneva, Switzerland, May 2001. 15. IEC. Mobile and Fixed Offshore Units – Electrical Installations – Part 7: Hazardous areas, International Standard IEC 61892-7, Edition 2.0, International Electrotechnical Commission (IEC), Geneva, Switzerland, 2007. 16. IMO MODU Code, Code For The Construction And Equipment Of Mobile Offshore Drilling Units, International Marine Organization (IMO). 2010 Edition. 17. Mannan, Sam. Lees’ Loss Prevention in the Process Industries, Volumes 1-3 - Hazard Identification, Assessment and Control (4th Edition). Elsevier, 2012. 18. Nolan, D.P. Application of HAZOP and What-If Safety Reviews to the Petroleum, Petrochemical and Chemical Industries. William Andrew Publishing/Noyes, 1994. 19. Simons, Stefaan J.R. Concepts of Chemical Engineering 4 Chemists. Royal Society of Chemistry, 2007. 20. Safety of Life at Sea - SOLAS Consolidated Edition, 2012.
