Brockham Oil Field
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BROCKHAM OIL FIELD Supplementary Hydrogeological Risk Assessment in Support of Permit Variation Application for a Groundwater Activity for the Injection of Process Waters Prepared for: Angus Energy Weald Basin No.3 Limited SLR Ref: 422.07154.00002 Version No: Issue Rev 6 August 2020 Angus Energy Limited Brockham Oil Field Hydrogeological Risk Assessment for Injection of Process Waters SLR Ref No: 200825__422_07154_00002_Brockham_Injection_Issue_Rev_06 422.07154.00002 August 2020 BASIS OF REPORT This document has been prepared by SLR Consulting Limited with reasonable skill, care and diligence, and taking account of the manpower, timescales and resources devoted to it by agreement with Angus Energy Weald Basin No.3 Limited (the Client) as part or all of the services it has been appointed by the Client to carry out. It is subject to the terms and conditions of that appointment. SLR shall not be liable for the use of or reliance on any information, advice, recommendations and opinions in this document for any purpose by any person other than the Client. Reliance may be granted to a third party only in the event that SLR and the third party have executed a reliance agreement or collateral warranty. Information reported herein may be based on the interpretation of public domain data collected by SLR, and/or information supplied by the Client and/or its other advisors and associates. These data have been accepted in good faith as being accurate and valid. The copyright and intellectual property in all drawings, reports, specifications, bills of quantities, calculations and other information set out in this report remain vested in SLR unless the terms of appointment state otherwise. This document may contain information of a specialised and/or highly technical nature and the Client is advised to seek clarification on any elements which may be unclear to it. Information, advice, recommendations and opinions in this document should only be relied upon in the context of the whole document and any documents referenced explicitly herein and should then only be used within the context of the appointment. Angus Energy Limited Brockham Oil Well Hydrogeological Risk Assessment for Injection of Process Waters SLR Ref No: 422.07154.00002 Filename: 200825__422_07154_00002_Brockham_Injection_Issue_Rev_06 August 2020 CONTENTS INTRODUCTION ............................................................................................................... 4 1.1 Background ............................................................................................................................... 4 1.2 Objective ................................................................................................................................... 4 ADDITIONAL INFORMATION REQUIRED ........................................................................... 5 2.1 Environment Agency Decision .................................................................................................. 5 2.2 Water Injection Proposals and Justification .............................................................................. 5 2.3 Protection of Overlying Aquifers and Well Integrity ................................................................. 7 2.3.1 Re-Interpretation of Seismic Data ................................................................................................................................... 7 2.3.2 Formation Pressure and Barriers ..................................................................................................................................... 9 2.3.3 Well Integrity .................................................................................................................................................................. 12 2.3.4 Probabilistic Analysis of Fluid Migration ....................................................................................................................... 16 2.4 Operational Procedures .......................................................................................................... 16 2.5 Groundwater Monitoring ........................................................................................................ 16 2.6 Biocide and Demulsifier .......................................................................................................... 17 SUMMARY AND CONCLUSIONS ...................................................................................... 18 DOCUMENT REFERENCES FIGURES Figure 2-1 Formation Water Salinity in Wealden Basin ....................................................................... 6 Figure 2-2 Volume of Fluid Produced and Injected .............................................................................. 9 Figure 2-2-3 Barriers to Flow from Reservoir ..................................................................................... 11 Figure 2-4 Schematic Construction of Well BRX3 ............................................................................... 13 Figure 2-5 2003 USIT Cement Bond Log ............................................................................................. 14 Figure 2-6 Comparison of 1987 and 2003 Cement Bond Logs ........................................................... 15 Page 2 Angus Energy Limited Brockham Oil Well Hydrogeological Risk Assessment for Injection of Process Waters SLR Ref No: 422.07154.00002 Filename: 200825__422_07154_00002_Brockham_Injection_Issue_Rev_06 August 2020 APPENDICES Appendix 01: Permit Appendix 02: Environment Agency Decision Appendix 03: Geochemical Implications for Produced Water Injection into Brockham Oilfield Appendix 04: Well Integrity Report Appendix 05: Monitoring Sheets Appendix 06: Geology Report Appendix 07: Probabilistic Analysis of Fluid Migration Appendix 08: Operational Procedures and PID’s Appendix 09: Biocide and Demulsifier Material Safety Data Sheets Page 3 Angus Energy Limited Brockham Oil Well Hydrogeological Risk Assessment for Injection of Process Waters SLR Ref No: 422.07154.00002 Filename: 200825__422_07154_00002_Brockham_Injection_Issue_Rev_06 August 2020 Introduction 1.1 Background Angus Energy Weald Basin No.3 Limited (Angus Energy) has commissioned SLR Consulting to prepare a supplementary Hydrogeological Risk Assessment (HRA) to support an application to vary Permit EPR/BL9763IN/V004 to allow the injection of produced water at Brockham Oilfield, Betchworth, Surrey, RH3 7AU for the purpose of aiding the production of oil from the oil reservoir. The National Grid Reference for the centre of the site is TQ 18840 48672. The site is operated by Angus Energy Weald Basin No3 (AE). An Environment Agency (EA) initiated application to vary the permit was made on 20th July 2017 (Application reference number EPR/BL9763IN/V004) under the Environmental Permitting (England and Wales) Regulations 2016 (EP Regulations), regulation 34(1), which requires the EA to periodically review permits. The application included a groundwater activity to inject produced water resulting from the extraction of hydrocarbons from both the Portland Sand Formation and the Kimmeridge Clay Formation back into the Portland Sand Formation. The discharge of produced water into groundwater within the oil-bearing formation is considered as a direct discharge to groundwater and a permit can only be granted provided it does not compromise the achievement of any of the environmental objectives relating to groundwater in Article 4 of the Water Framework Directive (WFD). There are however exemptions including: “The injection of water containing substances resulting from the operations for exploration and extraction of hydrocarbons or mining activities, and injection of water for technical reasons, into geological formations from which hydrocarbons or other substances have been extracted…….” The EA concluded that based on the information supplied they still had concerns regarding the proposal to continue re-injecting at this location using the existing well and therefore they decided to remove the groundwater activity from the application. A copy of the permit and the reasoning behind removing the groundwater activity is given in Appendix 01 and 02 respectively. 1.2 Objective The objective of this supplementary HRA is to present the additional information requested by the EA. It is not proposed to reproduce the background information presented in the original HRA1 and that report should be read in conjunction with this supplementary report. 1 SLR (September 2018) Brockham Oil Well. Hydrogeological Risk Assessment in Support of Re-Permit Application. Report ref. 180927_422_07154_00001_01_Brockham_Schedule_5_HRA_Rev_5_Issue. Page 4 Angus Energy Limited Brockham Oil Well Hydrogeological Risk Assessment for Injection of Process Waters SLR Ref No: 422.07154.00002 Filename: 200825__422_07154_00002_Brockham_Injection_Issue_Rev_06 August 2020 Additional Information Required 2.1 Environment Agency Decision The EA identified the following areas that required clarification or further information: • Well integrity • Operational procedures • Groundwater monitoring During further discussions with the Environment Agency (‘Pre-application advice – Enhanced service’ letter dated 17/07/2020) it was agreed that AE would also provide further interpretation of seismic mapping, and drawings showing both surface expressions of faulting and the juxtaposition of faults at reservoir depth. This includes the position of fault boundaries in the vicinity the target reservoir formation and the locations of these in