Hazop Surface Gas and Mud Handling Systems During Drilling Operations

SPE/IADC-173117-MS

Experiences, Challenges, and Common Recommendations fromPerforming HAZOP Studies to Identify Potential Hazards Associated toSurface 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, 1719 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 tocorrection by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers or the International Association of DrillingContractors, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of PetroleumEngineers 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 andOPerability (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-disciplinedteams that combine the operations, engineering, and process safety personnel from both the oil companyand the drilling contractor.

IntroductionDuring the rig intake process, HAZOP studies are used to review the surface gas and mud handlingsystems 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 deficienciesare 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 systematicrisk identification tool used by a multidiscipline team to assess the potential design and operationaldeficiencies of facilities. The HAZOP methodology uses a series of guidewords to examine potentialdeviations from normal operating conditions. The deviations are then examined to identify potentialhazards 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 studiesalso 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:

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 operateand the purpose of the system, see Table 1.

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Table 1Nodes 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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Identify the potential causes and consequences of credible worst case hazards in a systematic andcomprehensive manner. Typical questions include: What can go wrong? What are the potentialeffects and severity?

Identify and evaluate the existing mitigation measures (safeguards or barriers) and their effec-tiveness for each scenario (these include engineered systems and procedural or administrativecontrols associated with hazard prevention, detection, control, mitigation, and response).

Assess the risk presented by the identified potential hazard scenario by addressing the severity ofthe worst credible consequence and the likelihood of the hazardous event (including a reasonableevaluation of the effectiveness of the existing safeguards).

Recommend additional possible mitigation or control measures for consideration to improve thesafety of the facility.

Note: With respect to the surface gas and mud handling system HAZOP studies, the severity isdetermined by assessment of the worst credible consequence while excluding the intended mitigation of

Figure 1HAZOP Process

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the safeguards (i.e., assumes that all safeguards fail). The term credible means what is physicallypossible, not whether such consequences have ever occurred or might occur.

Make-up of the HAZOP TeamThe HAZOP technique relies on a team whose membership includes a broad range of knowledge andexperience in design and operation of the system(s). A successful surface gas and mud handling systemHAZOP study is conducted by a multi-disciplinary team with knowledge of the rigs equipment,functionality, well characteristics, drilling programme, operations, and potential failure modes. TheHAZOP 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 alsosupplement the core team described above. This broad participation in the surface gas and mud handlingsystem HAZOP typically also enhances participants knowledge and understanding of the equipment andsystems under review.

Information Essential for an Effective HAZOPThe availability of up-to-date Process Safety Information (PSI) is essential for an efficient and accurateHAZOP [7, 18, and 19]. This means that the changes that have occurred at the facility have been capturedand are reflected in the information and drawings. Important information to include in a HAZOP is a setof 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 gasdetection 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 equipmentand 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 neighboringfacilities [onshore rigs only])

Typical personnel distribution on the rig Inspection and testing results, maintenance records, operational history, and current condition ofequipment to be reviewed during HAZOP

Maintenance procedures Design basis for vessel sizing, venting, and operating limits for system components (Mud GasSeparator, 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 theexecution of the HAZOP study.

Scope of the Surface Gas and Mud Handling System HAZOP StudyThe surface gas and mud handling systems are divided into sections, called nodes, to allow the HAZOPteam go through the process in a systematic way one node at a time. Nodes are specific to individualdrilling programmes. The nodes commonly used in the surface gas and mud handling HAZOPs aredescribed in Table 1.

Selection of Guidewords and DeviationsGuidewords are combined with process parameters (see Table 2) to create deviations from the designintent and initiate a brainstorming exercise. The brainstorming exercise is used to identify potential causesthat could generate the deviation. If a cause is identified that has the potential to generate a processparameter deviation, then the associated scenario is developed, the risk is assessed, the safeguards areidentified, and risk reduction opportunities are evaluated.

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Table 2Common guidewords used in the Surface Gas and Mud Handling system HAZOP studies

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Table 3Common findings and recommendations in surface gas and mud handling system HAZOP studies (Note: these are notranked 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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Some common guidewords are: more, less, no, reverse, and other than [7, 14, 17, 19]. Thedeviations typically used for surface gas and mud handling system HAZOP studies are described in Table2.

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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Common findings and recommendationsThis section summarises common findings and recommendations in HAZOP studies conducted on rigsurface 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 mitigatea 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.

ConclusionsA consistent approach is required for the assessment and management of risks and to enable drillingcontractors and operators to consistently apply risk management to effectively integrate HSE into theiroperations [12, 13]. The application of the HAZOP methodology to review the surface gas and mudhandling systems on drilling rigs has permitted operators and drilling companies, by working together, tosystematically identify and mitigate risks by assessing potential design and operational deficiencies beforethe rig starts operation, in a mutually beneficial process. A number of recommendations were suggestedas means to further reduce the risk to both the drilling contractor and the operator. These recommendationsand learnings have been collected and evaluated to identify common themes that have been shared acrossregions and drilling contractors.

Common recommendations have included:

Conduct specialized risk assessments to further understand risks (e.g., gas dispersion study forhydrocarbon 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 designlimits (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 andreact to an undesired scenario (e.g., health/degradation of MGS liquid leg)

Enhance inspection and preventative maintenance requirements for a number of critical equip-ment/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 processand 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 operationalrequirements.

References1. 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 ManagementProgram for Offshore Operations, API Recommended Practice 75, Third Edition, AmericanPetroleum Institute, Washington DC, May 2008.

4. API. Specifications for Choke and Kill Systems, API Specification 16C, First Edition, AmericanPetroleum Institute, Washington DC, July 2010.

5. API. Specifications for Control Systems for Drilling Well Control Equipment and ControlSystems for Diverter Equipment, API Specification 16D, Second Edition, American PetroleumInstitute, 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 ProcessSafety (CCPS) of the American Institute of Chemical Engineers (AIChE), New York, New York,2008.

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9. DNV. Safety Principles and Arrangements. Offshore Standard DNV-OS-A101. Det NorskeVeritas. 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, De-

cember 199112. 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, Swit-zerland, 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 DrillingUnits, International Marine Organization (IMO). 2010 Edition.

17. Mannan, Sam. Lees Loss Prevention in the Process Industries, Volumes 1-3 - Hazard Identifi-cation, Assessment and Control (4th Edition). Elsevier, 2012.

18. Nolan, D.P. Application of HAZOP and What-If Safety Reviews to the Petroleum, Petrochemicaland 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.

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