ERCBH2S A Model for Calculating Emergency Response and ...

[Pages:265]ERCBH2S

A Model for Calculating Emergency Response and Planning Zones for Sour Wells, Sour Pipelines and Sour Production Facilities

Volume 1: Technical Reference Document, Version 1.20

ERCBH2S was developed for the Energy Resources Conservation Board (ERCB) by: Michael J. Zelensky, M.Sc., P.Eng. PSAQM Inc. (Public Safety and Air Quality Management) Brian W. Zelt, Ph.D., P.Eng. Zelt Professional Services Inc.

The project was managed by Gary Neilson, B.Sc. (Hons), P.Phys. of the ERCB's Field Surveillance and Operations Branch. The Emergency Management Group's patience and creative suggestions are gratefully acknowledged. Clearstone Engineering Ltd. provided the real fluids thermodynamic program ERCBFLASH. Special thanks go to Dr. David J. Wilson, P.Eng. of the University of Alberta, who provided expert technical guidance and several new solutions for hazard analysis implemented in the models. This project has benefited from a review by stakeholders. The Canadian Association of Petroleum Producers also sponsored a peer-review of the science, provided funding for the batch input function and participated in a pilot project to gain feedback on the model. Thank-you all for your comments and support.

ENERGY RESOURCES CONSERVATION BOARD ERCBH2S: A Model for Calculating Emergency Response and Planning Zones for Sour Wells, Sour Pipelines, and Sour Production Facilities, Volume 1: Technical Reference Document, Version 1.20

December, 2010

Published by

Energy Resources Conservation Board Centennial Place Suite 1000, 250 ? 5 Street SW Calgary, Alberta T2P 0R4 Telephone: 403-297-8311 Fax: 403-297-7040 Web site: ercb.ca

Liability Disclaimer

These models, software and documentation were prepared by the ERCB (Energy Resources Conservation Board) and/or Clearstone Engineering Ltd., to the specifications set by ERCB. ERCB warrants that the SOFTWARE will perform substantially in accordance with the provided documentation. Neither ERCB and/or Clearstone Engineering Ltd., nor any person acting on their behalf, makes any warranty, guarantee, or representation, expressed or implied, that the software and related materials, without limitation, are free of errors, are consistent with any standard of merchantability or will meet user's requirements for a particular application, that any calculations performed by the software are correct or accurate, that the software is compatible with particular computer systems, computer peripherals and other software packages, or that the software will run uninterrupted.

EXCEPT AS PROVIDED ABOVE, THIS DOCUMENTATION AND SOFTWARE IS LICENSED "AS IS" WITHOUT WARRANTY AS TO ITS PERFORMANCE. NO OTHER WARRANTIES APPLY. ERCB AND/OR CLEARSTONE ENGINEERING LTD., DISCLAIM ALL OTHER WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THIS LIMITED WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS. YOU MAY HAVE OTHERS, WHICH VARY FROM PROVINCE TO PROVINCE.

IN NO EVENT SHALL ERCB AND/OR CLEARSTONE ENGINEERING LTD., OR THEIR SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS PROFITS, BUSINESS INTERRUPTION, LOSS OF BUSINESS INFORMATION, CONSEQUENTIAL DAMAGES, OR OTHER PECUNIARY LOSS, HOWSOEVER ARISING OUT OF THE USE, ATTEMPTED USE OF OR INABILITY TO USE THIS PRODUCT, EVEN IF ERCB AND/OR CLEARSTONE ENGINEERING LTD. HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

The equations and analysis in this report are part of on-going hazard analysis project. Some of the assumptions and approximations have not yet been validated.

The user is cautioned that the author and sponsors assume no responsibility for the accuracy of these models, or for errors or omissions in this report.

Table of Contents

1 INTRODUCTION ..................................................................................................................1 2 USER INPUTS .......................................................................................................................3

2.1 Administrative............................................................................................................... 3 2.2 Calculation Controls ..................................................................................................... 4 2.3 Gas Pipeline .................................................................................................................. 5 2.4 Gas Well........................................................................................................................ 6 2.5 Liquid Pipeline or Liquid Well ..................................................................................... 6 2.6 Sour Gas Composition .................................................................................................. 8 2.7 Advanced User Selected Case ...................................................................................... 9 3 PHYSICAL PROPERTIES ..................................................................................................10 3.1 Constants..................................................................................................................... 10 3.2 Sour Gas...................................................................................................................... 10 3.3 Air ............................................................................................................................... 12 4 ERCBFLASH - REAL FLUID PROPERTIES ....................................................................14 4.1 Inputs........................................................................................................................... 14 4.2 Outputs........................................................................................................................ 15 5 RELEASE DESCRIPTION ..................................................................................................17 5.1 Gas Pipeline ................................................................................................................ 17

5.1.1 Initial and Exit Conditions .............................................................................. 17 5.1.2 Transient Mass Release Rate .......................................................................... 19 5.1.3 Effective Length.............................................................................................. 21 5.1.4 ESD Valve Settings to Reduce the Release .................................................... 22 5.1.5 ESD Valve Closure on Low Pressure ............................................................. 23 5.1.6 ESD Valve Closure on Pressure Rate of Change............................................ 24 5.1.7 ESD Valve Closed Manually or Remotely ..................................................... 25 5.1.8 Effective Release Duration and Effective Steady Mass Release Rate............ 25 5.1.9 Effect of Ignition or Stoppage of Flow on Duration and Rate........................ 26 5.1.10 Modelled Release Duration and Modelled Steady Mass Release Rate .......... 26 5.1.11 Actual Volume of H2S Released..................................................................... 27 5.1.12 Licensed Volume of H2S ................................................................................ 27 5.2 Gas Well...................................................................................................................... 28 5.2.1 Steady Mass Release Rate .............................................................................. 28 5.2.2 Release Duration before Ignition or Stop Flow .............................................. 28 5.2.3 Initial and Exit Conditions .............................................................................. 29 5.3 Liquid Pipeline or Liquid Well ................................................................................... 31 5.3.1 Steady Mass Release Rate .............................................................................. 31 5.3.2 Release Duration before Shut-In or Ignition................................................... 31 5.3.3 Initial and Exit Conditions .............................................................................. 32 5.3.4 Oil Effluent Pipeline Licensed Volume of H2S .............................................. 33 5.4 Gathering System Equivalent Lengths........................................................................ 34 6 JET EXPANSION - INITIAL BEHAVIOUR OF RELEASE .............................................37 6.1 E Plane ........................................................................................................................ 38 6.2 Q Plane........................................................................................................................ 38 6.3 D Zone to R Plane....................................................................................................... 38 6.4 R Plane Inputs to ERCBSLAB ................................................................................... 39

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7 DISPERSION METEOROLOGY ........................................................................................41 7.1 Site Elevation and Atmospheric Pressure ................................................................... 42 7.2 Ambient Temperature ................................................................................................. 42 7.3 Relative Humidity....................................................................................................... 42 7.4 Surface Roughness...................................................................................................... 42 7.5 Wind Speed and Stability Class Screening Matrix ..................................................... 43 7.5.1 Minimum Turbulence ..................................................................................... 44 7.6 Ambient Measurement Height.................................................................................... 45

8 ERCBSLAB - UNIGNITED H2S RELEASE DISPERSION MODELLING .....................46 8.1 ERCBSLAB Inputs..................................................................................................... 46 8.2 SLAB Enhancements to Produce ERCBSLAB .......................................................... 48 8.2.1 Buoyancy Flux in a High Velocity Jet with Droplet Evaporation .................. 48 8.2.2 Plume Rise Limits........................................................................................... 49 8.2.3 Vertical Buoyant Release Air Entrainment and Source Conditions ............... 51 8.2.4 Correction to Vertical Dense Release Plume Rise.......................................... 51 8.2.5 Kinetic Energy in Energy Conservation Equation.......................................... 52 8.3 Steady to Transient Transformation............................................................................ 53 8.3.1 Neutrally Buoyant Releases............................................................................ 53 8.3.2 Dense Releases................................................................................................ 54 8.3.3 Transition from Continuous to Puff Mode...................................................... 54 8.4 Parallel Airflow or Complex Terrain? ........................................................................ 55

9 H2S EXPOSURE ..................................................................................................................57 9.1 Outdoor Concentration Fluctuations........................................................................... 57 9.1.1 Steady Outdoor Load ...................................................................................... 58 9.1.2 Transient Outdoor Load.................................................................................. 58 9.2 Transient Indoor Concentrations................................................................................. 58 9.2.1 Indoor Load for Steady Outdoor Concentration ............................................. 59 9.2.2 Indoor Load for Transient Outdoor Concentration......................................... 59 9.3 Hazard Distance Outputs ............................................................................................ 60 9.4 H2S Exposure Endpoints............................................................................................. 61

10 WORST EXPECTED ZONES .............................................................................................62 10.1 Probability of Dispersion Conditions in Alberta ........................................................ 63 10.2 Adjustments to Approach ........................................................................................... 64

11 SENSITIVITY OF PREDICTIONS TO INPUTS................................................................65 11.1 User Inputs .................................................................................................................. 65 11.1.1 Elevation ......................................................................................................... 65 11.1.2 Gas Pipeline .................................................................................................... 65 11.1.3 Gas Well.......................................................................................................... 66 11.1.4 Liquid Pipeline/Well....................................................................................... 66 11.1.5 Sour Gas Composition .................................................................................... 66 11.2 ERCB Default Inputs .................................................................................................. 67 11.2.1 Source Parameters........................................................................................... 67 11.2.2 Meteorology.................................................................................................... 67 11.2.3 Exposure ......................................................................................................... 68 11.3 Gas Pipeline Sensitivity .............................................................................................. 68 11.4 Gas Well Sensitivity ................................................................................................... 72 11.5 Liquid Pipeline/Well Sensitivity................................................................................. 75

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12 COMPARISON TO PREVIOUS ERCB EPZ......................................................................78 12.1 Gas Pipelines............................................................................................................... 78 12.2 Gas Wells .................................................................................................................... 83 12.3 Liquid Pipelines or Liquid Wells................................................................................ 87

13 REFERENCES .....................................................................................................................88 APPENDIX A: ERCBFLASH Thermodynamics Program APPENDIX B: Dispersion, Toxic Load and Odour Calculations for Transient Releases

from Pipeline Ruptures and Gas Well Blowouts APPENDIX C: Selection of the Drag Coefficient for Uncontrolled Sour Gas Releases

List of Figures Figure 6.1 Jet Expansion Regions showing the Source Modelling Planes ............................... 37 Figure 12.1 Old ERCB Nomographs for Pipeline EPZ............................................................... 79 Figure 12.2 New ERCB EPZ for 6" pipeline with selected ESD valve closure ......................... 81 Figure 12.3 New ERCB EPZ for 10" pipeline with selected ESD valve closures...................... 82 Figure 12.4 Old ERCB Nomographs for Well EPZ.................................................................... 84 Figure 12.5 New ERCB EPZ for drilling/servicing gas well with selected ignition times......... 85 Figure 12.6 New ERCB EPZ for producing gas well with selected ignition times .................... 86 Equation Section (Next)

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