Solan Production Chemical Permit SAT Chemical Risk Assessment for Platform and SOST Installation, Commissioning and Operation

Transcription

1 Solan Production Chemical Permit SAT for Platform and SOST Installation, Commissioning and Operation

2 REV ISSUE DATE STATUS AMENDMENT DETAILS ORIGINATE D BY APPROVED B1 30/05/14 1 st Draft Submitted for client review Genesis Genesis B2 04/06/14 Final Client comments incorporated Genesis Genesis B3 14/08/14 Variation 1 To add REDA chemicals Genesis Premier B4 26/08/14 B5 04/09/14 B6 24/09/14 B7 03/10/14 B8 19/11/14 B9 27/01/15 B10 03/03/15 B11 10/03/15 B12 15/04/15 B13 01/05/15 B14 05/05/15 B15 30/06/15 B16 21/10/15 B17 18/11/15 Variation 1 Version 2 Variation 1 Version 3 Variation 1 Version 4 Variation 1 Version 5 Variation 2 Version 1 Variation 2 Version 2 Variation 2 Version 3 Variation 2 Version 4 Variation 3 Version 1 Variation 4 Version 1 Variation 4 Version 2 Variation 5 Version 1 Variation 7 Version 1 Variation 8 Version 1 Update to address Marine Scotland comments Update to address Marine Scotland comments Update to address Marine Scotland comments Update to address Marine Scotland comments and amend to align with changes to PLA/90 CP/342, 343 & 345 Genesis Genesis Genesis Genesis Premier Premier Premier Premier Update to add production chemicals Genesis Premier Update to address Marine Scotland comments Update to address client comments, update for biocide dosing of seawater caisson and to reflect changes to PLA/90 CP/347 & 348 Genesis Genesis Premier Premier Update to address MS comments Genesis Premier Update for additional application of EC6527G Update to include new chemical permit (CP/tba) under PLA/90. Update to EC6527G and addition of an EC6198A Application Update to include additional pumps on the EC6198A application and add EC6527H Increase of chemical usage, addition of chemicals and amendment to text. Addition of biocide EC6718A and updates for discharge of ballast water during commissioning Genesis Genesis Genesis Genesis Genesis Genesis This document contains proprietary information belonging to Premier and must not be wholly or partially reproduced nor disclosed without prior written permission from Premier. Premier Premier Premier Premier Premier Premier The master copy of this document is held electronically within Premier s Document Management System. If you are using a paper copy or a CD issue of this document, it is your responsibility to ensure it is the latest version. Page 2

3 1 CHEMICAL RISK ASSESSMENT 1.1 Background This forms part of the Chemical Permit SAT (CP/371) which supports Production MAT (PRA/157) for the Installation, Commissioning and Operational Phases of the operations at the Solan field. A Pipeline MAT (PLA/90) and associated SATs were submitted in May 2014 to support the PWA and DepCon applications. Sections 2 to 4 of this assess the installation and commissioning phases and Sections 5 and 6 assess production operations at Solan. Page 3

4 2 INSTALLATION PHASE 2.1 Background A chemical risk assessment has been carried out for the purpose of the proposed Subsea Oil Storage Tank (SOST) installation operations. All the chemicals that are planned to be used comply with OCNS and the Offshore Chemicals Regulations 2002 (as amended). Details of the chemicals that are planned to be used are in the Chemical Permit SAT. CHARM calculations have been undertaken, where applicable, to assess the potential environmental risk of chemical discharges to sea from surface installations. All discharges were modelled assuming a batch discharge; assumptions for batch dilution factors are provided below. Batch dilution factors (BDFs) are calculated from: Density of the discharged fluid (normally equivalent to seawater), not the density of the product. The permitted range within CHARM is 1.03 to 1.7 g/cm 3. Discharge rate of the discharged fluid. The permitted range within CHARM is 60 to 180 m 3 /hour. Total volume of fluid discharged. The permitted range within CHARM is 3 to 120 m 3. If the discharge parameters exceed the permitted range, the worst case BDF of allowable within CHARM will be used. If the discharge parameters are below the permitted range, the minimum values will be used to calculate a BDF of Note that BDFs are only calculated for chemicals that are discharged to the environment and for which CHARM modelling is applicable. Osborne Adams calculations were undertaken to assess the potential environmental risk of the discharge of chemicals subsea. Discharge rates assumed a discharge of 50 m 3 over seven hours. In all instances T1 was found to be more than T2, indicating that the releases will not have a significant effect on the marine environment. None of the chemicals proposed to be used in the operations have an RQ >1 / an HQ >1 / SUB warning / OCNS category of A, B or C. Page 4

5 None of the chemicals proposed to be used in these operations were found to present a risk to the environment; therefore, the overall effects of marine discharges on the benthic communities and the marine environment are not expected to be significant. 2.2 Description of Chemical Use During the seven hour SOST installation period the tank was flooded and lowered to the seabed. The SOST has flooding valves in its base and vent valves at the top to allow water from beneath to displace the air. The SOST was pre-dosed onshore with corrosion inhibitor, biocide and dye (see Table 2-1) which, as the interior filled with seawater, was diluted to the required dosage. The tank was free flooded with a contingency air supply connected to ensure a controlled descent. Once the tank was set down the flood and vent valves were closed and the vessels and air lines disconnected. No egress of water occurred however a contingency of 50 m 3 discharge was included. The remaining chemicals will be retained in the system before being flowed back to the platform via the 12 water return line prior to being discharged to sea during the first fill of the tank. Chemical Name For additional details of the SOST please see Section 2.2 of the EIA Justification. Chemical Function Application Type Table 2-1 Chemical Summary Cefas Template Product Label Action Level Category Expiry Date RO IM B221 Biocide Batch Gold 10/09/16 RO HY M738 Dye Batch Gold 19/07/16 RO HY M700 Oxygen scavenger Batch Gold 26/02/16 Following on from the SOST installation as described above, once the tank is on the seabed, the valves used for flooding the tank will be removed in order to fit blank plates and REDA chemical sticks will be inserted (see Table 2-2). Although the storage tank already contains a Biocide, Dye and Oxygen Scavenger, further products are required as several vent/flooding valves are to be cut and flange connections are to be disconnected and replaced with blind flanges. Page 5

6 Chemical sticks will be inserted at each new flange connection where tank containment is broken. 24 flanged joints will be made up with 100 g RO HY C350, 100 g RO HY B238, 100 g RO HY V658 and 100 g RO HY M779 chemical sticks. Subsea discharge of chemical sticks is not expected during the course of this operation. However, as a worst case, it is assumed up to 10 g RO HY C350, 10 g RO HY B238, 10 g RO HY V658 and 10 g RO HY M779 (10% of each stick mass) may partially dissolve / discharge subsea during insertion of the sticks at each flanged connection. The remaining chemicals will be retained in the system before being flowed back to the platform via the 12 water return line prior to being discharged to sea during the first fill of the tank. 10% discharge of RO HY C350, RO HY B238, RO HY V658 and RO HY M779 has been modelled using the Osborne-Adams method and the results show that they are unlikely to have an impact on the marine environment (see Appendix A). The further 90% discharge has been assessed using CHARM and all RQs generated are <1, indicating that the discharges will not have a significant impact on the marine environment. The total volume of the SOST is estimated at 50,000 m 3 and this has been used to calculate dosages after dilution. This volume is sufficiently great to also allow for the volume of fluid flowed into the tank from the pipelines. A summary of the discharges is presented in Table 3-1. Chemical Name RO HY B238 RO HY C350 RO HY M779 RO HY V658 Stick Chemical Function Application Type Table 2-2 Chemical Summary Cefas Template Product Label Action Level Category Expiry Date Biocide Batch 2 SUB 4 Gold 16/07/2015 Corrosion Inhibitor Batch 2 SUB 4 Gold 21/07/2015 Dye Batch 2 SUB 4 Gold 16/07/2015 Oxygen Scavenger Batch 3 SUB 4 Gold 16/07/2015 Page 6

7 The supplier (REDA) does not intend to fully certify RO HY B238, RO HY C350, RO HY M779 and RO HY V658 Sticks. The six month field trial templates were applied for as the current formulation of the products attracts a warning after review of the first sets of ecotox data. The warning for the products is due to the binder used, as discussed in the justification. Therefore REDA does not intend to fully certify the materials as they are already actively working on replacements with improved environmental characteristics. The function of the products in the storage tank is identical to their function during the six month field trial for pipeline hydrotesting. The fate of the chemicals left in the system after installation of the pipelines and tank will be either: displaced downhole; discharged to sea from the topsides during the first fill of the SOST; or flowed to the tanker during the first cargo off-load. Page 7

8 3 SOST COMMISSIONING / FIRST FILL After the first cargo off-load there will be no discharge of production chemicals to sea, unless necessary for the commissioning of equipment in order to ensure long term discharges are minimised. A commitment was made in the Environmental Statement that production will be shut in when water injection is not available. The P2 well will not be available at the time of first oil. At first oil, all installation chemicals in P1 infield pipelines will be flowed to the topsides with the produced fluids, then on to the tank where they will partition into the water phase, and then back to the platform via the 12 water return line prior to being discharged to sea during the first fill of the tank. All installation chemicals in the 10 oil export line will be flowed to the tank, then back to the platform via the 12 water return line prior to being discharged to sea during the first fill of the tank. All installation chemicals in the 12 ballast water line will be flowed to the platform and discharged to sea during the first fill of the tank. All installation chemicals in the SOST will be flowed back to the platform via the 12 water return line prior to being discharged to sea during the first fill of the tank. During the first cargo offloading from the tank, all the installation chemicals in the 24 displacement line will be flowed in to the tank. During the subsequent tank fill it is expected that these chemicals will flow back to the platform via the 12 ballast water return line prior to being injected down hole. However, there is the potential for these chemicals to be discharged to sea during first fill therefore this has been risk assessed as part of the chemical permit SAT (PRA/157 CP/371). During the first cargo offloading from the tank, all the installation chemicals in the offloading system (i.e. the 24 offloading line and the OLS and the hose) will be offloaded to the tanker. The exception to this is the chemical sticks used in SOST remedial works. These chemicals sticks will be discharged to sea during first fill therefore this has been risk assessed as part of the chemical permit SAT (PRA/157 CP/371). Page 8

9 During the initial water injection, the chemicals left in the W1 & W2 infield pipelines will be flowed downhole and will not be discharged to sea. A total of 1.6 kg of RO HY B238, 1.6 kg of RO HY C350, 1.6 kg of RO HY M779 and 1.6 kg of RO HY V658 is calculated for the chemicals remaining in the pipelines. The use of these chemicals has previously been permitted and therefore only their discharge is applied for here. These discharges have been added to those applied for in this permit (i.e. the sticks inserted following installation of the SOST, 1.08 kg of RO HY B238, 1.08 kg of RO HY C350, 1.08 kg of RO HY M779 and 1.08 kg of RO HY V658) to give a total of 2.86 kg of RO HY B238, 2.86 kg of RO HY C350, 2.86 kg of RO HY M779 and 2.86 kg of RO HY V658 which will be discharged to sea. A total of kg of Monoethylene Glycol (and all dilutions) (Reda), kg of RO IM B221 and 6.04 kg of RO HY M738 is calculated for the chemicals remaining in the pipelines. These have been added to the chemicals already in the SOST (pre-fill) to give a total of 22, kg of RO IM B221, 5, kg of RO HY M738 as well as 32,092.2 kg RO HY M700 remaining in the SOST. The total volume of the SOST is estimated at 50,000 m 3 and approximately 7,500 m 3 discharge has been accounted for during tie-ins. The remaining volume of 42,500 m 3 has been used to calculate dosages after dilution. This volume is sufficiently greater to also allow for the volume of fluid flowed into the SOST from the pipelines. A summary of the discharges is presented in Table 3-1. These discharges have been modelled using CHARM (with the exception of MEG which is PLONOR and OCNS E) and all RQs generated are <1 (with the exception of RO HY M700 which is further justified), indicating that the discharges will not have a significant impact on the marine environment. A BDF of 5.3E-04 was calculated using the density of seawater (1.031 g/cm 3 ), a rate of 60 m 3 /h (the minimum available in the EOSCA calculator) and a volume of 120 m 3 based on a worst case total discharge volume of 1000 m 3 /day, see EIA Justification MAT Table 4.1. This is based on the annual oil production rate. The rate at which oil enters the SOST determines the rate at which water is flushed out Page 9

10 of the SOST. A figure of 1,000 m 3 /day has been used in order to account for potential variation in the rate of oil production and to ensure that the worst case potential discharge volume per day is assessed. None of the chemicals proposed to be used in these operations were found to present a risk to the environment; therefore, the overall effects of marine discharges on the benthic communities and the marine environment are not expected to be significant. 3.1 Solan Umbilical Displacement Chemicals Flushing of the umbilical chemical cores is critical for start-up operation. The shipping fluid contained in the umbilical chemical cores, and if applicable the spacer chemicals required to displace it, will be displaced to the reservoir before commencing the initial start-up (at least one week in advance). This will ensure production chemical availability at the wellhead/downhole injection point concurrent with production. These activities will take place during the Hook-Up and Commissioning (HUC) phase. The current chemical permit covers the routine chemical injection operations required during routine production activities. In addition, a one-off displacement operation is required for each umbilical during HUC. As per routine operations this activity will displace all umbilical fluids downhole with no expected discharge to sea. During commissioning, the Aquaglycol 24F left in the umbilicals will be displaced downhole. A mutual solvent will be used to clean the umbilicals prior to charging with production chemicals. The mutual solvent will also be discharged down hole. Page 10

11 PLA-90 CP-342 PLA-90 CP-345 PLA-90 CP-346 Table 3-1 Summary of discharges PLA-90 CP-347 PLA-90 CP-348 SUB TOTAL PRA-157 CP-371 TOTAL Discharge dosage (mg/l) RX RX RX N/A RX-9034A RO HY C RO HY B RO HY M RO HY V RO IM B RO HY M RO HY M RX RX MEG (REDA) N/A Page 11

12 4 CHEMICAL JUSTIFICATIONS FOR INSTALLATION AND COMMISSIONING This section gives a detailed description of and justification for the chemicals to be used during installation and commissioning. Further risk based justification has been included in the following circumstances: Where RQs >1; HQ>1 (Silver, White, Orange, Blue and Purple); Chemicals contain components identified for ; or Non-CHARMable chemicals with OCNS groups that indicate a significant toxic potential (i.e. OCNS category A, B or C). Chemical name MEG (and all dilutions) Supplier REDA Oilfield UK Ltd Function Other Injection point n/a MEG (and all dilutions) remaining in the pipelines will be discharged topsides on start-up. A total of kg will be discharged. This is not expected to have a significant impact on the marine environment as it is a small amount and this product is PLONOR and HQ Category E. PLONOR HQ category E Identified for RQ N/A Chemical name RO IM B221 (1 of 2) Supplier REDA Oilfield Function Biocide Injection Point n/a RO IM B221 is a biocide which was pre-dosed into the SOST onshore. As the tank was lowered into position on the seabed, the interior filled with seawater (via flooding valves in the bottom), which diluted RO IM B221 to the required dosage. Air was displaced from vent valves in the top of the tank. No egress of water occurred however a contingency of 50 m 3 discharge has been included in the chemical permit application. The tank will remain filled with seawater until commissioning. Treatment with RO IM B221 biocide is therefore required to preserve the integrity of the tank. The discharge has been modelled using the Osborne-Adams method and T1>T2 therefore it is unlikely to have an impact on the marine environment (see Appendix A). The remainder of the chemical will be retained in the system during installation and then will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for CHARM data Assumptions RQ n/a Dosage 540 mg/l Seawater will enter the tank (through valves on the underside) and air Fraction discharged 0.1% and chemical egress will leave the tank (though valves on the topside) over the 7 hour operation period. CHARM algorithm code CNA Discharge code OTH Page 12

13 Chemical name RO IM B221 (2 of 2) Supplier REDA Oilfield Function Biocide Injection Point n/a RO IM B221 is a biocide which was pre-dosed into the SOST onshore. 0.1% of the chemical will be discharged during installation and the remainder will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for CHARM data Assumptions RQ <1 Dosage 540 mg/l Following the potential 0.1% discharge subsea during installation, the Fraction discharged 99.9 % remainder of the chemical will be retained in the system until commissioning when it will be discharged from the topsides. CHARM algorithm code CWO Discharge code BAT Chemical name RO HY M738 (1 of 2) Supplier REDA Oilfield Function Dye Injection Point n/a RO HY M738 is required to check for leaks in the system. RO HY M738 is a dye which was pre-dosed into the SOST onshore. As the tank was lowered into position on the seabed, the interior filled with seawater (via flooding valves in the bottom), which diluted RO HY M738 to the required dosage. Air was displaced from vent valves in the top of the tank. No egress of water occurred however a contingency of 50 m 3 discharge has been included in the chemical permit application. The discharge has been modelled using the Osborne-Adams method and T1>T2 therefore it is unlikely to have an impact on the marine environment (see Appendix A). The remainder of the chemical will be retained in the system during installation and then will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for CHARM data Assumptions RQ n/a Dosage 128 mg/l Seawater will enter the tank (through valves on the underside) and air Fraction discharged 0.1% and chemical egress will leave the tank (though valves on the topside) over the 7 hour operation period. CHARM algorithm code CNA Discharge code OTH Chemical name RO IM M738 (2 of 2) Supplier REDA Oilfield Function Dye Injection Point n/a RO HY M738 is required to check for leaks in the system. 0.1% of the chemical was discharged during installation and the remainder will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for RQ <1 CHARM data Assumptions Dosage 128 mg/l Following the potential 0.1% discharge subsea during installation, the Fraction discharged 99.9 % remainder of the chemical will be retained in the system until Page 13

14 commissioning when it will be discharged from the topsides. CHARM algorithm code CWO Discharge code BAT Chemical name RO HY M700 (1 of 2) Supplier REDA Oilfield Function Oxygen scavenger Injection Point n/a RO HY M700 is a corrosion inhibitor which was pre-dosed into the SOST onshore. As the tank was lowered into position on the seabed, the interior filled with seawater (via flooding valves in the bottom), which diluted RO HY M700 to the required dosage. Air was displaced from vent valves in the top of the tank. No egress of water occurred however a contingency of 50 m 3 discharge has been included in the chemical permit application. The tank will remain filled with seawater until commissioning. Treatment with RO HY M700 oxygen scavenger is therefore required to preserve the integrity of the tank. The discharge has been modelled using the Osborne-Adams method and T1>T2 therefore it is unlikely to have an impact on the marine environment (see Appendix A). The remainder of the chemical will be retained in the system during installation and then will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for CHARM data Assumptions RQ n/a Dosage 756 mg/l Seawater will enter the tank (through valves on the underside) and air Fraction discharged 0.1% and chemical egress will leave the tank (though valves on the topside) over the 7 hour operation period. CHARM algorithm code CNA Discharge code OTH Chemical name RO HY M700 (2 of 2) Supplier REDA Oilfield Function Oxygen Scavenger Injection Point n/a RO HY M700 is a corrosion inhibitor which was pre-dosed into the SOST onshore. 0.1% of the chemical will be discharged during installation and the remainder will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for RQ >1 CHARM data Assumptions Dosage 756 mg/l Following the potential 0.1% discharge subsea during installation, the Fraction discharged 99.9 % remainder of the chemical will be retained in the system until commissioning when it will be discharged from the topsides. CHARM algorithm code CWO Discharge code BAT Justification: An RQ = 4.2 was generated for the discharge of RO HY M700, therefore its discharge may have an impact on the marine environment. A dosage higher than the Cefas template dosage was required due to treatment duration and mode of deployment. Due to its surface active nature it will adsorb onto particles while it is contained within the SOST therefore due to its adsorption and biodegradation properties it will have low bio availability when ultimately released to the marine environment, anticipated to be approximately 3 months after the initial fill. RO HY M700 is biodegradable and will disperse rapidly when released. The product is water soluble and the hydrodynamic regime around the Solan area is generally energetic enough to ensure that any discharge will be rapidly diluted and dispersed, minimising any potential impact on the marine environment Page 14

15 Chemical name RO HY B238 (1 of 2) Supplier REDA Oilfield Function Biocide Injection Point n/a RO HY B238 is a biocide stick which was inserted after flooding of the tank and before the blank plates are fitted. A worst case discharge of 10% of the stick mass during insertion has been assumed. With the exception of the 10% release during insertion, the rest of the chemical will be retained in the system during installation and then discharged from the topsides during commissioning. 10% discharge has been modelled using the Osborne-Adams method and T1>T2 therefore it is unlikely to have an impact on the marine environment (see Appendix A). The remaining 90% will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for CHARM data Assumptions RQ n/a Dosage 120 mg/l (10% of each stick mass) may partially dissolve / discharge subsea during Fraction discharged 10 % insertion of the sticks at each flanged connection. The remaining chemical will be retained in the system until commissioning when it will be discharged from the topsides. CHARM algorithm code CNA Discharge code OTH Justification: The REDA Sticks have a SUB warning due to the use of a Polyethylene Glycol binder which is used as the binder/matrix to hold the active ingredients, which shows poor biodegradation. The toxicity is also high (worst case aquatic toxicity of 3.35 mg/l) which is necessary to fulfil its purpose as a biocide. In order to develop free versions REDA Oilfield are continuing to review and develop formulations and options to improve the stick binder package, moving to lower molecular weight polyethylene glycols which are expected to have improved biodegradation. Simultaneously we are also exploring other binding options to eliminate the warnings from this range of products. Osborne Adams modelling has shown that any subsea discharge is not likely to have a significant impact on the marine environment. The manufacturer is aware that this product is a UK National Plan level 4 chemical and that it must be replaced, or discharges to the marine environment eliminated, or continued use and/or discharge must be formally justified by the end of December Chemical name RO HY B238 (2 of 2) Supplier REDA Oilfield Function Biocide Injection Point n/a RO HY B238 is a biocide stick which was inserted after flooding of the tank and before the blank plates are fitted. 90% of the chemical will be retained in the system during installation and then discharged subsea during commissioning. This 90% will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for CHARM data Assumptions RQ <1 Dosage mg/l Following the potential 10% discharge subsea during insertion of the Fraction discharged 90 % sticks, the remaining 90% of chemical will be retained in the system until commissioning when it will be discharged from the topsides. CHARM algorithm code CWO Discharge code BAT Page 15

16 Justification: The REDA Sticks have a SUB warning due to the use of a Polyethylene Glycol binder which is used as the binder/matrix to hold the active ingredients, which shows poor biodegradation. The toxicity is also high (worst case aquatic toxicity of 3.35 mg/l) which is necessary to fulfil its purpose as a biocide. In order to develop free versions REDA Oilfield are continuing to review and develop formulations and options to improve the stick binder package, moving to lower molecular weight polyethylene glycols which are expected to have improved biodegradation. Simultaneously we are also exploring other binding options to eliminate the warnings from this range of products. CHARM modelling has shown that the discharge from the topsides is not likely to have a significant impact on the marine environment. The manufacturer is aware that this product is a UK National Plan level 4 chemical and that it must be replaced, or discharges to the marine environment eliminated, or continued use and/or discharge must be formally justified by the end of December Chemical name RO HY C350 (1 of 2) Supplier REDA Oilfield Function Corrosion Inhibitor Injection Point n/a RO HY C350 is a corrosion inhibitor stick which was inserted after flooding of the tank and before the blank plates are fitted. A worst case discharge of 10% of the stick mass during insertion has been assumed. With the exception of the 10% release during insertion, the rest of the chemical will be retained in the system during installation and then discharged from the topsides during commissioning. 10% discharge has been modelled using the Osborne-Adams method and T1>T2 therefore it is unlikely to have an impact on the marine environment (see Appendix A). The remaining 90% will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for CHARM data Assumptions RQ n/a Dosage 100 mg/l (10% of each stick mass) may partially dissolve / discharge subsea during Fraction discharged 10% insertion of the sticks at each flanged connection. The remaining chemical will be retained in the system until commissioning when it will be discharged from the topsides. CHARM algorithm code CNA Discharge code OTH Justification: The REDA Sticks have a SUB warning due to the use of a Polyethylene Glycol binder which is used as the binder/matrix to hold the active ingredients, which shows poor biodegradation. The toxicity is also high (worst case aquatic toxicity of 1.02 mg/l). In order to develop free versions REDA Oilfield are continuing to review and develop formulations and options to improve the stick binder package, moving to lower molecular weight polyethylene glycols which are expected to have improved biodegradation. Simultaneously we are also exploring other binding options to eliminate the warnings from this range of products. Osborne Adams modelling has shown that any subsea discharge is not likely to have a significant impact on the marine environment. The manufacturer is aware that this product is a UK National Plan level 4 chemical and that it must be replaced, or discharges to the marine environment eliminated, or continued use and/or discharge must be formally justified by the end of December Chemical name RO HY C350 (2 of 2) Supplier REDA Oilfield Function Corrosion Inhibitor Injection Point n/a Page 16

17 RO HY C350 is a corrosion inhibitor stick which was inserted after flooding of the tank and before the blank plates are fitted. 90% of the chemical will be retained in the system during installation and then discharged subsea during commissioning. This 90% will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for CHARM data Assumptions RQ <1 Dosage mg/l Following the potential 10% discharge subsea during insertion of the Fraction discharged 90 % sticks, the remaining 90% of chemical will be retained in the system until commissioning when it will be discharged from the topsides. CHARM algorithm code CWO Discharge code BAT Justification: The REDA Sticks have a SUB warning due to the use of a Polyethylene Glycol binder which is used as the binder/matrix to hold the active ingredients, which shows poor biodegradation. The toxicity is also high (worst case aquatic toxicity of 1.02 mg/l). In order to develop free versions REDA Oilfield are continuing to review and develop formulations and options to improve the stick binder package, moving to lower molecular weight polyethylene glycols which are expected to have improved biodegradation. Simultaneously we are also exploring other binding options to eliminate the warnings from this range of products. CHARM modelling has shown that the discharge from the topsides is not likely to have a significant impact on the marine environment. The manufacturer is aware that this product is a UK National Plan level 4 chemical and that it must be replaced, or discharges to the marine environment eliminated, or continued use and/or discharge must be formally justified by the end of December Chemical name RO HY M779 (1 of 2) Supplier REDA Oilfield Function Dye Injection Point n/a RO HY M779 is a dye stick which was inserted after flooding of the tank and before the blank plates are fitted. A worst case discharge of 10% of the stick mass during insertion has been assumed. With the exception of the 10% release during insertion, the rest of the chemical will be retained in the system during installation and then discharged from the topsides during commissioning. 10% discharge has been modelled using the Osborne-Adams method and T1>T2 therefore it is unlikely to have an impact on the marine environment (see Appendix A). The remaining 90% will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for CHARM data Assumptions RQ n/a Dosage 100 mg/l (10% of each stick mass) may partially dissolve / discharge subsea during Fraction discharged 10 % insertion of the sticks at each flanged connection. The remaining chemical will be retained in the system until commissioning when it will be discharged from the topsides. CHARM algorithm code CNA Discharge code OTH Page 17

18 Justification: The REDA Sticks have a SUB warning due to the use of a Polyethylene Glycol binder which is used as the binder/matrix to hold the active ingredients, which shows poor biodegradation. It is not likely to be toxic (worst case aquatic toxicity of mg/l). In order to develop free versions REDA Oilfield are continuing to review and develop formulations and options to improve the stick binder package, moving to lower molecular weight polyethylene glycols which are expected to have improved biodegradation. Simultaneously we are also exploring other binding options to eliminate the warnings from this range of products. Osborne Adams modelling has shown that any subsea discharge is not likely to have a significant impact on the marine environment. The manufacturer is aware that this product is a UK National Plan level 4 chemical and that it must be replaced, or discharges to the marine environment eliminated, or continued use and/or discharge must be formally justified by the end of December Chemical name RO HY M779 (2 of 2) Supplier REDA Oilfield Function Dye Injection Point n/a RO HY M779 is a dye stick which was inserted after flooding of the tank and before the blank plates are fitted. 90% of the chemical will be retained in the system during installation and then discharged subsea during commissioning. This 90% will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for CHARM data Assumptions RQ <1 Dosage mg/l Following the potential 10% discharge subsea during insertion of the Fraction discharged 90 % sticks, the remaining 90% of chemical will be retained in the system until commissioning when it will be discharged from the topsides. CHARM algorithm code CWO Discharge code BAT Justification: The REDA Sticks have a SUB warning due to the use of a Polyethylene Glycol binder which is used as the binder/matrix to hold the active ingredients, which shows poor biodegradation. It is not likely to be toxic (worst case aquatic toxicity of mg/l). In order to develop free versions REDA Oilfield are continuing to review and develop formulations and options to improve the stick binder package, moving to lower molecular weight polyethylene glycols which are expected to have improved biodegradation. Simultaneously we are also exploring other binding options to eliminate the warnings from this range of products. CHARM modelling has shown that the discharge from the topsides is not likely to have a significant impact on the marine environment. The manufacturer is aware that this product is a UK National Plan level 4 chemical and that it must be replaced, or discharges to the marine environment eliminated, or continued use and/or discharge must be formally justified by the end of December Chemical name RO HY V658 Stick (1 of 2) Supplier REDA Oilfield Function Oxygen Scavenger Injection Point n/a RO HY V658 Stick is an oxygen scavenger stick which was inserted after flooding of the tank and before the blank plates are fitted. A worst case discharge of 10% of the stick mass during insertion has been assumed. With the exception of the 10% release during insertion, the rest of the chemical will be retained in the system during installation and then discharged from the topsides during commissioning. 10% discharge has been modelled using the Osborne-Adams method and T1>T2 therefore it is unlikely to have an impact on the marine environment (see Appendix A). The remaining 90% will be discharged via topsides and has been risk assessed Page 18

19 using CHARM. PLONOR HQ category Gold Identified for RQ n/a CHARM data Assumptions Dosage 100 mg/l (10% of each stick mass) may partially dissolve / discharge subsea during Fraction discharged 10 % insertion of the sticks at each flanged connection. The remaining chemical will be retained in the system until commissioning when it will be discharged from the topsides. CHARM algorithm code CNA Discharge code OTH Justification: The REDA Sticks have a SUB warning due to the use of a Polyethylene Glycol binder which is used as the binder/matrix to hold the active ingredients, which shows poor biodegradation. It is not likely to be toxic (worst case aquatic toxicity of mg/l). In order to develop free versions REDA Oilfield are continuing to review and develop formulations and options to improve the stick binder package, moving to lower molecular weight polyethylene glycols which are expected to have improved biodegradation. Simultaneously we are also exploring other binding options to eliminate the warnings from this range of products. Osborne Adams modelling has shown that any subsea discharge is not likely to have a significant impact on the marine environment. The manufacturer is aware that this product is a UK National Plan level 4 chemical and that it must be replaced, or discharges to the marine environment eliminated, or continued use and/or discharge must be formally justified by the end of December Chemical name RO HY V658 Stick (2 of 2) Supplier REDA Oilfield Function Oxygen Scavenger Injection Point n/a RO HY V658 Stick is an oxygen scavenger stick which was inserted after flooding of the tank and before the blank plates are fitted. 90% of the chemical will be retained in the system during installation and then discharged subsea during commissioning. This 90% will be discharged via topsides and has been risk assessed using CHARM. PLONOR HQ category Gold Identified for RQ <1 CHARM data Assumptions Dosage mg/l Following the potential 10% discharge subsea during insertion of the Fraction discharged 90 % sticks, the remaining 90% of chemical will be retained in the system until commissioning when it will be discharged from the topsides. CHARM algorithm code CWO Discharge code BAT Justification: The REDA Sticks have a SUB warning due to the use of a Polyethylene Glycol binder which is used as the binder/matrix to hold the active ingredients, which shows poor biodegradation. It is not likely to be toxic (worst case aquatic toxicity of mg/l). In order to develop free versions REDA Oilfield are continuing to review and develop formulations and options to improve the stick binder package, moving to lower molecular weight polyethylene glycols which are expected to have improved biodegradation. Simultaneously we are also exploring other binding options to eliminate the warnings from this range of products. CHARM modelling has shown that the discharge from the topsides is not likely to have a significant impact on the marine environment. The manufacturer is aware that this product is a UK National Plan level 4 chemical and that it must be replaced, or discharges to the marine environment eliminated, or continued use and/or discharge must be formally justified by the end of December Page 19

20 4.1 Osborne Adams Calculations Page 20

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27 5 PRODUCTION PHASE In the production phase, the Solan development will require a high level of chemical treatment and production chemistry management, including: Produced oil and water treatment chemicals: o Asphaltene Inhibitor o Biocide o Demulsifier o Oil Antifoam o Scale Inhibitor Seawater injection treatment chemicals: o Biocide o Oxygen Scavenger o Scale inhibitor o Water Antifoam Detergent / cleaning fluids to maintain topsides The following document details the chemicals required, dosage rates, quantities and injection points. Solan will operate as a closed system once online and there are no planned discharges of production chemicals, with the exception of chlorination, which will take place routinely in the seawater system to control the potential blockage of pipes and corrosion. Discharges of installation chemicals will occur as a one-off during first fill. There are no planned discharges occurring thereafter as Premier are committed to no production without re-injection. The exceptions are utility products such as detergents and hydraulic fluids which may occasionally be discharged. Any discharge of these products has been fully risk assessed. All chemicals specified for use in the Solan development and on this application are registered with CEFAS as per standard Premier procedures. The most up to date CEFAS ranked list was used to source templates in order to complete this application. Premier will continue to liaise with chemical suppliers to ensure that the chemicals will be re-registered or will be submitted for re-registration at the appropriate time (generally 8-weeks prior to the expiry date). During initial start-up and commissioning of the process, continuing past the first fill of the SOST, ballast water from the SOST will be discharged to sea. The first fill overboard discharge volume is anticipated to be 406,000 m 3. This is expected to take 3 months. Page 27

28 Post first fill of the SOST the water injection system will be commissioned. When available, all ballast water will be re-injected and discharge to sea will only occur if the system is unavailable. The expected uptime post commissioning of the water injection system is 95%. Should the water injection system become unavailable ballast water will be discharged to sea via the sea water disposal caisson C CHARMable chemicals have undergone a chemical risk assessment using CHARM in order to estimate the potential for adverse impact on the marine environment as a result of discharges from Solan. The risk assessment has taken into account the total fluids volumes (see Table 5-1) to calculate the Risk Quotient (RQ). The daily volumes in Table 5-1 have been calculated using the P10 profile in order to assess the worst case scenario in terms of environmental impact. The availabilities used in the profiles are as follows: No water injection facility initially for approximately 3 months; and Water injection uptime of 95% to begin three months after first oil. These figures represent the worst case in terms of potential environmental impact and are all annual averages with operational efficiencies applied, therefore, these figures may differ from those presented elsewhere. Table 5-1 Production data used in CHARM Year Total fluids (m 3 /day) Oil production (m 3 /day) Produced water (m 3 /day) Ballast water (m 3 /day) Seawater Injection (m 3 /day) Total Water Injection (m 3 /day) ,618 1, , , ,485 2, , ,733 The general assumptions made in the preparation of this application and during the calculations of the RQs are detailed in Section 6. Specific assumptions for each product are detailed in the relevant justification. Page 28

29 5.1 Production/Process Chemicals A number of production chemicals will be utilised in the Solan process stream to increase the efficiency of the production processes and to protect the integrity of the production and export facilities and the reservoir. These production chemicals provide a wide range of functions including prevention of scale and improving the separation of oil in water during processing. 5.2 Produced Water Treatment A water injection system is installed to inject treated produced water and treated seawater into the reservoir in order to maintain the required pressures and optimise oil and gas production. Products used within the PWRI system do not end up in the marine environment as they are contained downhole and Premier is committed to no production without re-injection. The products listed under continuous use/discharge for 2015 are not part of the preservation fluid and will be used when production begins at Solan. All water produced and used through Solan is planned to be reinjected. If the seawater and produced water reinjection facilities are down then the field will be shut in until this is back online. 5.3 Seawater Treatment Seawater is required to make up any shortfall of re-injection water below the required injection rate. It undergoes treatment before co-mingling with produced water and ballast water returned from the SOST (see Figure 5-1). Seawater is lifted via pumps, dosed with sodium hypochlorite generated in situ and passed through coarse filters. The filtered seawater is then directed to two locations either injection or cooling water systems. The injection water is directed to the fine filters and deaerator where oxygen scavenger is injected along with water antifoam. Biocide will be injected into the system as required. The treated seawater is not planned to be discharged as it is re-injected and contained downhole. The cooling water is routed as cooling medium for all platform users before being routed overboard via the sea water disposal caisson. 5.4 Water Injection System A scale inhibitor is injected into the water injection system (produced water, treated seawater and ballast water returned from the SOST) before produced water and seawater mix prior to injection into the reservoir (see Figure 5-1). The injection Page 29

30 quality water is not planned to be discharged as it is re-injected and contained downhole. 5.5 SOST Biocide The SOST is constructed from carbon steel as is the internal pipework. There is a high risk of corrosive bacteria forming, particularly biofilms, therefore biocidal protection is essential to protect the integrity of the SOST and internal pipework. This will only be used from start-up from the first fill of the SOST with oil. The application of biocide will be reduced as required based on a robust monitoring and sampling regime. There is a high risk of bacterial growth in the SOST because raw seawater will be used for displacement, which will contain bacteria and is oxygenated. The seawater will then be allowed to sit in stagnant conditions ideal for the proliferation of biofilm that leads to microbial influenced corrosion. Therefore, a biopenetrant is required to prevent establishment and aid removal of biofilm. A glutaraldehyde based product (EC6178A) is required to protect the SOST. EC6718A carries a warning, but considering its performance compared to industry standard, single component formulations, it is considered that this is the best possible option to protect the Solan SOST from the threat of microbiological influenced corrosion. There are non-sub products (those without surfactants) available but these products do not provide the bio-penetration required in this application to combat biofilm which has the potential to be a significant problem in the SOST. A more environmentally friendly biocide is available (EC6527H) and testing has shown that this product is likely to be effective in the water injection system but not the SOST system. EC6527H is a tetrakis hydroxymethyl phosphonium sulphate (THPS) based product which degrades relatively fast, providing a potential food source for bacteria. If biofilms are established, a much higher biocide concentration is then required. THPS has no biofilm penetration properties, so must be used with a surfactant to improve efficacy. Page 30

31 Figure 5-1 Process Flow Diagram - Seawater Treatment and Water Re-Injection with chemical injection points highlighted Page 31

32 5.6 Utility Chemicals Cleaning Chemicals There are requirements for various detergent/cleaning materials including general purpose rig wash to clean light hydrocarbons from the platform decks and turbine wash used to perform offline washes to maintain turbine integrity. There will be zero discharge of these chemicals as they will mix with fluid in the drainage system and be re-injected. Cleaning chemicals will be discharged to sea via the sea water disposal caisson C Hydraulic Fluid Hydraulic fluid is used to maintain pressure in the subsea system and to actuate control valves and to prevent the ingress of seawater. 5.7 Annual Usage Figures A contingency factor of 10% has been built in to the annual usage figures for all products. Therefore, it is not possible to directly convert tonnages into dosage in the case of continuously used chemicals. The injection rates are decided following multidisciplinary assessment, laboratory experimentation, manufacturer recommendations and field results. It is from these results, combined with the forecast production data and resultant effect on processing conditions, that the estimated annual quantity is calculated. For multi-well batch treatment operations environmental modelling has been performed on the maximum batch size used in the operation to represent a worst case scenario. However, a unique batch size is calculated for every well dependent on a number of factors including the flow characteristics and distance from the point of chemical injection to required chemical treatment. Therefore, the total use recorded for batch use products will not always correspond to the number of wells to be treated multiplied by the maximum batch use. The total use may be lower as not all wells will be treated with the maximum batch size. Batch chemicals do not contain a contingency threshold, as each operation differs in nature and realistic estimates are difficult to quantify. Page 32