Nor th W est Hut t on Decommissioning P rogramme North West Hutton Decommissioning Programme BP External Affairs Department J Farburn Industrial Estate, anuar Dyce, Aberdeen AB21 7PB Tel +44 (0)1224 832000 y 20 05 www.bp.com/northwesthutton February 2005 Contents List CONTENTS LIST Glossary of terms x Section 1 INTRODUCTION 1 1.1 North West Hutton Decommissioning Programmes 2 Section 2 EXECUTIVE SUMMARY 5 2.1 Introduction and Recommendations 5 2.2 Background Information 8 2.2.1 Environmental Setting 8 2.2.2 Facilities to be Decommissioned 8 2.3 Principles Used to Assess Decommissioning Activity 10 2.3.1 Introduction 10 2.3.2 Legal Requirements 10 2.3.3 Methodology and Evaluation Process 11 2.4 Assessment of Decommissioning Options 13 2.4.1 Alternative Use and Re-use 13 2.4.2 Topsides Decommissioning 13 2.4.3 Jacket Decommissioning 14 2.4.4 Drill Cuttings Pile 18 2.4.5 Pipeline Decommissioning – PL 147 and PL 148 19 2.5 Interested Parties Consultation 21 2.6 Debris Clearance and Site Monitoring 21 2.7 Onshore Treatment and Disposal of Materials 21 2.8 Cost Summary and Schedule 22 2.9 Legacy 22 Section 3 BACKGROUND INFORMATION 23 3.1 Introduction 23 3.2 Layout of the Facilities in this Programme 23 3.3 Adjacent Facilities 24 3.4 Physical, Meteorological and Oceanographic Conditions 25 3.5 Fishing and Commercial Activities 26 3.5.1 Fishing 26 3.5.2 Commercial Activities 27 3.6 Ecology 27 3.6.1 Plankton and Primary Production 27 3.6.2 Seabed Communities 27 3.6.3 Fish and Shellfish 28 3.6.4 Marine Mammals 29 3.6.5 Seabirds 29 3.7 Conservation Status 33 3.7.1 Introduction 33 3.7.2 Annex I Habitats 33 3.7.3 Annex II Species 33 3.8 Onshore Sites for Dismantling and Treatment 34 References 36 North West Hutton Decommissioning Programme February 2005 i Contents List Section 4 DESCRIPTION OF ITEMS TO BE DECOMMISSIONED 37 4.1 Introduction 37 4.2 Description of the North West Hutton Platform 37 4.2.1 Support Structure 37 4.2.2 Topsides 41 4.3 Description of the North West Hutton Drilling Template and Wells 43 4.4 Description of the North West Hutton Pipelines 43 4.4.1 10” Natural Gas Export / Import Pipeline (PL174) 44 4.4.2 20” Oil Pipeline (PL148) 45 4.5 Description of the North West Hutton Drill Cuttings Pile 47 4.6 Debris and Other Material 49 References 50 Section 5 INVENTORY OF MATERIALS 51 5.1 Introduction 51 5.2 Topsides 51 5.3 Support Structures 52 5.3.1 Grout Densitometers 53 5.4 Well Related Material 53 5.5 Pipelines 53 5.6 Drill Cuttings Pile 54 5.7 Debris and Other Seabed Items 54 5.8 Onshore Treatment and Disposal of Materials 54 References 55 Section 6 GUIDING PRINCIPLES AND SCREENING PROCESS 57 6.1 Introduction 57 6.2 Guiding Principles 57 6.3 Assessment Methodology 58 6.4 Comparative Assessment Criteria 59 6.4.1 Safety 59 6.4.2 Environmental Impact 60 6.4.3 Social Impact 60 6.4.4 Technical Feasibility 61 6.4.5 Costs and Financial Management 61 6.5 Method for High Level Option Selection 62 6.6 Results of High Level Option Selection 62 6.6.1 Reuse of Installation 62 6.6.2 Decommissioning the Platform 63 6.6.4 Drill Cuttings 64 6.6.5 Pipelines 65 References 65 ii North West Hutton Decommissioning Programme February 2005 Contents List Section 7 TOPSIDES DECOMMISSIONING 67 7.1 Introduction 67 7.2 Description of Possible Removal Methods 68 7.2.1 Offshore Deconstruction 68 7.2.2 Reverse Installation 69 7.2.3 Single Lift 71 7.3 Selection of Removal Method 71 7.3.1 Introduction 71 7.3.2 Assessment of Three Removal Methods 72 7.3.3 Comparison of Removal Methods 73 7.4 Reverse Installation Programme for Decommissioning the Topsides 73 7.4.1 Decommissioning of Wells and Removal of Conductors 73 7.4.2 Preparatory Work for Topsides Removal 74 7.4.3 Lifting and Transportation to Shore 75 7.4.4 Receiving and Dismantling Onshore 75 References 76 Section 8 JACKET DECOMMISSIONING 77 8.1 Introduction and Background 77 8.2 Present Condition of Jacket 77 8.3 Assessment of Jacket Removal Options 79 8.3.1 Introduction 79 8.3.2 Summary and Screening of Removal Techniques 80 8.4 Assessment of Jacket Removal by Offshore Deconstruction 81 8.4.1 Introduction 81 8.4.2 Jacket Removal Overview 81 8.5 Comparative Assessment of Jacket Removal Options 81 8.5.1 Introduction 81 8.6 Assessment of the Option of Full Jacket Removal 83 8.6.1 Technical Description of Removal Operations 83 8.6.2 Technical Assessment of Full Jacket Removal 85 8.6.3 Safety Evaluation of Full Jacket Removal 88 8.6.4 Environmental Impacts of Full Jacket Removal 90 8.6.5 Societal Impacts of Full Jacket Removal 90 8.6.6 Summary of Full Jacket Removal 91 8.7 Assessment of Option of Partial Removal of the Footings 91 8.7.1 Technical Evaluation of Partial Removal of the Footings 91 8.7.2 Safety Evaluation of Partial Removal of the Footings 93 8.7.3 Environmental Impacts of Partial Removal of the Footings 93 8.7.4 Societal Impacts of Partial Removal of the Footings 94 8.7.5 Summary of Partial Removal of the Footings 94 8.8 Assessment of the Option of Jacket Removal to the Top of the Footings 94 8.8.1 Technical Evaluation of Removal of the Jacket to the Top of the Footings 95 8.8.2 Safety Evaluation of Removal of the Jacket to the Top of the Footings 95 8.8.3 Environmental Impacts of Removal of the Jacket to the Top of the Footings 95 8.8.4 Societal Impacts of Removal of the Jacket to the Top of the Footings 95 8.8.5 Summary of Removal of the Jacket to the Top of the Footings 96 8.9 Cost Assessment 96 8.10 Comparative Assessment and Conclusions of Jacket Removal Evaluations 96 8.11 Recommended Decommissioning Option for the Jacket 98 References 99 North West Hutton Decommissioning Programme February 2005 iii Contents List Section 9 DRILL CUTTINGS 101 9.1 Introduction 101 9.2 Present Composition, Condition and Effects of the North West Hutton Drill Cuttings Pile 101 9.2.1 Introduction 101 9.2.2 History 101 9.2.3 Composition 103 9.2.4 Physical Nature of the Drill Cuttings Pile 103 9.2.5 Understanding of the North West Hutton Drill Cuttings Pile and the Surrounding Area 104 9.3 Assessment of Decommissioning Options for the Drill Cuttings Pile 106 9.4 Option ‘Leave in-situ to degrade naturally’ 107 9.4.1 Description 107 9.4.2 Technical Feasibility 107 9.4.3 Environmental Impact 107 9.4.4 Societal Impact 108 9.4.5 Safety of Personnel 109 9.5 Option ‘Leave in-situ and Cover with Inert Material’ 109 9.5.1 Description 109 9.5.2 Technical Feasibility 111 9.5.3 Environmental Impact 111 9.5.4 Societal Impact 111 9.5.5 Safety of Personnel 111 9.6 Option ‘Excavate and Disperse the Drill Cuttings’ 112 9.6.1 Description 112 9.6.2 Technical Feasibility 112 9.6.3 Environmental Impact 112 9.6.4 Societal Impact 112 9.6.5 Safety of Personnel 113 9.7 Option ‘Retrieve and Dispose of Cuttings of Onshore or by Re-injection Offshore’ 113 9.7.1 Description 113 9.7.2 Technical Feasibility 114 9.7.3 Environmental Impact 115 9.7.4 Societal Impact 116 9.7.5 Safety of Personnel 116 9.8 Cost Assessment 117 9.9 Comparative Assessment of Options for the Drill Cuttings Pile 117 9.10 Recommended Decommissioning Option for the Drill Cuttings 119 References 120 iv North West Hutton Decommissioning Programme February 2005 Contents List Section 10 PIPELINES 121 10.1 Introduction 121 10.2 Applicable Techniques for Decommissioning the Pipelines 121 10.2.1 Pipelines Left in-situ 121 10.2.2 Techniques for Removing Pipelines 122 10.3 Decommissioning the 10” Gas Line PL 147 123 10.3.1 Items to be Decommissioned 123 10.3.2 Description of Options for the 10” Gas Line PL 147 127 10.3.3 Assessment of Options for 10” Gas Line PL 147 128 10.3.4 Recommended Decommissioning Option for the 10”Gas Line PL 147 129 10.4 Decommissioning the 20” Oil Line PL148 130 10.4.1 Items to be Decommissioned 130 10.4.2 Description of Options for the 20” Oil Line PL 148 131 10.4.3 Assessment of Options for the 20” Oil Line 133 10.4.4 Recommended Decommissioning Option for the 20”Oil Line PL 148 135 10.5 Combined Programme for the Two Pipelines 135 10.5.1 Rationale 135 10.5.2 Summary of the Decommissioning Programme for PL 147 and PL 148 135 10.5.3 Programme Timing and Schedule 137 10.5.4 Monitoring Programme for Material Left on the Seabed 138 References 138 Section 11 WELL ABANDONMENT AND CONDUCTOR REMOVAL 139 References 142 Section 12 INTERESTED PARTY CONSULTATION 143 12.1 Introduction 143 12.2 Consultation Plan and Schedule 143 12.3 Consultation Process 144 12.4 Consultation – Issues Raised 144 12.5 Independent Review Group 145 References 146 Section 13 COST SUMMARY FOR DECOMMISSIONING NORTH WEST HUTTON 147 Section 14 SCHEDULE 149 Section 15 LICENCES ASSOCIATED WITH DECOMMISSIONING NORTH WEST HUTTON 151 Section 16 PROJECT MANAGEMENT 153 16.1 Introduction 153 16.2 Health, Safety and Environment 153 16.3 Technical 154 16.4 Reporting 155 References 155 Section 17 DEBRIS CLEARANCE 157 North West Hutton Decommissioning Programme February 2005 v Contents List Section 18 PRE- AND POST- DECOMMISSIONING MONITORING MAINTENANCE AND POTENTIAL LIABILITIES 159 18.1 Pre-Decommissioning Monitoring 159 18.2 Post-Decommissioning Monitoring and Maintenance 159 Section 19 ENVIRONMENTAL STATEMENT SUMMARY 161 19.1 Introduction 161 19.2 Method Used to Assess and Compare Environmental Risks 161 19.3 Decommissioning the Topsides 167 19.3.1 Outcome: Decommissioning Topsides by Total Removal 167 19.3.2 Environmental Risks: Decommissioning the Topsides by Total Removal 167 19.4 Decommissioning the Jacket 168 19.4.1 Outcome: Decommissioning the Jacket by Total Removal 168 19.4.2 Environmental Risks: Decommissioning the Jacket by Total Removal 168 19.5 Decommissioning the Footings 168 19.5.1 Total Removal of the Footings 168 19.5.2 Partial Removal of the Footings 169 19.5.3 Leave the Footings in-situ and Monitor 169 19.5.4 Comparison of Outcomes for the Footings 170 19.6 Decommissioning the Drill Cuttings Pile 171 19.6.1 Leave in-situ and Monitor 171 19.6.2 Leave in-situ, Covered.