Guidance on calculating blowout rates and duration for use in environmental risk analyses Translated and updated version Norwegian Oil and Gas: Guidance on calculating blowout rates and duration for use with environmental risk analyses PREFACE This guidance on calculating blowout rates and duration for use in environmental risk analyses is an updated version in English of the Norwegian Oil and Gas Association´s Norwegian report entitled Retningslinjer for beregning av utblåsningsrater og - varighet til bruk ved analyse av miljørisiko. The original report was first published in 2004 and revised in 2007. It was prepared by Thomas Nilsen in Statoil with support from colleagues Nina E B Jacobsen, Arne Myhrvold, Espen Fyhn Nilsen (all Statoil) and Tone Roald (Hydro). Minor revisions and corrections have been made to this English edition by Thomas Nilsen. Before starting to translate and update the report in 2014, two Norwegian Oil and Gas expert networks were invited to comment on the original (Network on Environmental Risk and the Drilling Managers Forum). Relevant consultants (Add Wellflow, Acona, DNV GL and Akvaplan-niva) were also invited to comment on the 2007 report. Rolf E Gooderham has carried out the translation in close cooperation with Thomas Nilsen. Norwegian Oil and Gas also engaged Add Wellflow to prepare a new document with guidance for blowout rate simulations – data basis and scenario selection. This is intended to serve as a supplement to the existing guidance on the treatment of uncertainty related to blowout rates and duration in environmental risk analyses. It will provide a guideline for those involved in data collection and/or simulation of blowout rates for use in environmental risk analyses. The supplement offers an overview of data requirements and how the parameters can affect the results for various flow scenarios. The same networks and consultants were again invited to comment on this text. The responsible manager in Norwegian Oil and Gas is the manager, environment, who can be contacted via the main switchboard on +47 51 84 65 00. Norwegian Oil and Gas Association Vassbotnen 1, NO-4313 Sandnes P O Box 8065 NO-4068 Stavanger, Norway Tel: +47 51 84 65 00 Fax: +47 51 84 65 01 Website: www.norskoljeoggass.no E-mail: [email protected] Norwegian Oil and Gas: Guidance on calculating blowout rates and duration for use with environmental risk analyses Page: 1 Contents 1 SUMMARY ......................................................................................................................... 3 Abbreviations, notations and symbols ................................................................................ 4 Definitions ....................................................................................................................................... 4 2 INTRODUCTION.............................................................................................................. 8 3 APPROACH AND MAIN PRINCIPLES ................................................................... 10 3.1 Calculating blowout rate and duration as part of an environmental risk analysis ................................................................................................................................... 10 3.2 Framework for calculating blowout rate and duration ....................................... 12 3.3 Principles for the guidance ............................................................................................. 14 4 REFERENCE METHODOLOGY................................................................................. 16 4.1 Definition of blowout scenarios .................................................................................... 16 4.2 Presentation of uncertainty related to the course of a blowout ...................... 18 4.3 Blowout rate ......................................................................................................................... 20 4.4 Blowout duration ............................................................................................................... 22 4.5 Handling uncertainty in the calculations .................................................................. 25 4.5.1 On the use of models ..................................................................................................... 25 4.5.2 Determining probabilities and probability calculations ................................. 26 4.5.3 Collating rate and duration calculations for various scenarios and the scope and level of activities ........................................................................................ 27 5 GUIDANCE ....................................................................................................................... 28 5.1 Definition of blowout scenarios .................................................................................... 29 5.2 Presentation of uncertainty related to the course of a blowout ...................... 30 5.3 Blowout rate ......................................................................................................................... 31 5.4 Blowout duration ............................................................................................................... 31 5.5 Handling uncertainty in the calculations .................................................................. 32 5.5.1 Use of models ................................................................................................................... 32 5.5.2 Determining probabilities and probability calculations ................................. 32 5.5.3 Collating rate and duration calculations for different scopes and levels of activity ................................................................................................................................ 34 6 REFERENCES ................................................................................................................. 35 APPENDICES ....................................................................................................................... 36 A LOSS OF WELL CONTROL......................................................................................... 37 A.1. Drilling .............................................................................................................................. 38 B FIGHTING AND STOPPING A BLOWOUT ........................................................... 41 B.1. Active measures from the rig ................................................................................... 41 B.2. Bridging ............................................................................................................................ 42 B.3. Killing a blowout via a relief well ........................................................................... 42 B.4. Natural cessation of a blowout ................................................................................ 43 C HISTORY, CURRENT REGULATIONS AND PRACTICE .................................. 44 C.1. History .............................................................................................................................. 44 Norwegian Oil and Gas: Guidance on calculating blowout rates and duration for use with environmental risk analyses Page: 2 C.2. Key provisions in current regulations .................................................................. 44 C.3. Current practice ............................................................................................................ 46 D EXAMPLES OF APPLYING THE GUIDANCE ....................................................... 48 D.1. Example 1 – drilling a production well ................................................................ 48 D.2. Example 2 – drilling an exploration well............................................................. 58 D.3. Example 3 – accumulating rate and duration calculations from single operations to field level ................................................................................................... 66 SUPPLEMENTARY REPORT - DATA BASIS FOR BLOWOUT RATE SIMULATIONS .................................................................................................................... 76 1 INTRODUCTION............................................................................................................ 76 1.1 General.................................................................................................................................... 76 1.2 Governing documents, regulations and standards ................................................ 76 2 DATA REQUIREMENTS FOR MODELLING ........................................................ 77 2.1 General.................................................................................................................................... 77 2.2 Well location ......................................................................................................................... 77 2.3 Water depth .......................................................................................................................... 78 2.4 Drilling rig ............................................................................................................................. 78 2.5 Reservoir fluids ................................................................................................................... 78 2.6 Reservoir data.....................................................................................................................