Environmental Impact Factor (EIF) simulations related to Dagny field

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Scarlett Gilmore
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1 related to Dagny field Classification: Internal Status: Final Expiry date: Page 1 of 9

2 Classification: Internal Status: Final Expiry date: Page 2 of 9

3 Table of contents 1 Introduction Scope of work Input data Field data Scenarios for produced water amounts and oil in water concentrations Produced Water Composition Results References... 9 Classification: Internal Status: Final Expiry date: Page 3 of 9

4 1 Introduction The Environmental Impact Factor (EIF) is an environmental index quantifying the environmental risk of produced water discharges and is used for identification and prioritisation of alternative measures for risk reduction. The EIF is based on a combined environmental risk and hazard assessment, accounting for both composition and amount of the produced water discharge. A thorough description of the EIF and its practical application is given in Frost et al., 2009 (1) and Smit et al (2). 2 Scope of work In this document the EIF tool is applied for discharges of produced water from the Dagny Oil and Gas Field, which is under development. The EIF tool is used in order to compare the potential environmental benefit of alternative measures to reduce the potential impact of produced water discharges, and to form a basis for a cost-effective total approach to produced water management. 3 Input data 3.1 Field data The Dagny Field is located in the Norwegian Sea with geographical coordinates 58 34' 19,848" North and 01 41' 48,436" East. The discharge depth is 10 m below sea surface. 3.2 Scenarios for produced water amounts and oil in water concentrations For this study, EIF is calculated for 8 different scenarios listed in Table 1 below. These alternatives differ in oil (aliphatic hydrocarbons) concentration and produced water management solutions, as re-injection (E) and discharge to sea (A D) being the two options. The daily discharge rates for produced water amounts and the oil in water concentrations for Dagny presented in Table 1 are used for calculating the annual Environmental Impact Factor (EIF) for Dagny. Table 1: Produced water amounts and oil in water concentrations for Dagny Scenario Produced water discharge rate [Sm 3 /d] Oil in Water concentration [ppm] A A B B C C D D E 0 Re-injection Classification: Internal Status: Final Expiry date: Page 4 of 9

5 The oil in water concentrations were set based on both the maximum concentration, which is the upper limit of discharge by the authorities (29 ppm) and the probable lowest concentration, which can be obtained through an optimal design of the produced water handling (10 ppm). 3.3 Produced Water Composition For the EIF simulation, man-made chemicals are selected among the tentative products used for Gudrun Design basis, which were chosen from the project as comparable, for a worst case scenario i.e. products with highest potential environmental impact (i.e. hazardous properties) are selected and presented in Table 2 together with their injection rate, which equals their concentrations in produced water. Table 2: Chemicals and their concentrations in produced water Type of chemical to be used at Dagny Selected products for simulation based on products used at Gudrun Scale inhibitor SI Emulsion breaker DMO Flocculant WT Proposed injection rate in ppmv (mg/l) for Dagny Concentrations of natural occurring compounds for Dagny, are listed in Table 3, excluding the aliphatic hydrocarbon concentrations since it will vary for each scenario. In cooperation with the discipline ladder Flow Assurance the project came to the result that Norne oil will be the most representative oil regarding the natural occurring compounds. Therefore the values for 2009 for Norne were taken as input data for the EIF model for Dagny. Classification: Internal Status: Final Expiry date: Page 5 of 9

6 Table 3: Natural occurring compounds concentrations for Norne 2009 used in the EIF model for Dagny Compound Concentration (mg/l) Sum BTEX 23,3968 Sum Naphtalen 1, ring PAH 0, ring PAH 0,00066 Fenol C0-C3 8,81394 Alkylfenoler C4-C5 0,22522 Alkylfenoler C6-C9 0,00126 Zn 0,0063 Cu 0,00022 Ni 0,00117 Cd 0,00005 Pb 0,00028 Hg 0, Results The EIF results for all 8 scenarios for Dagny are presented in Table 4. Table 4: EIF results for Dagny Scenario PW discharge rate [Sm 3 /d[ Oil in Water concentration [ppm] A A B B C C D D E 0 Re-injection 0 EIF As can be seen in table 4, the maximum EIF value (EIF = 13) occurs for scenario A1, which has the highest discharge rate for produced water combined with the highest oil in water content. The EIF value for scenario A2 with the same discharge rate, but lower oil in water concentration (10 ppm) has been calculated to EIF = 10. Generally these EIF values are low. For all other scenarios EIF has been calculated to EIF = 0. Classification: Internal Status: Final Expiry date: Page 6 of 9

7 Figure 1 shows, which components are contributing to EIF = 13 in scenario A1. Generally the natural occurring compounds are dominating the contribution to EIF with about 98 %. Main contributor is aliphates (42 %) followed by phenols C4-C5 (17 %) and 2-3 ring PAH (10 %). Added chemicals are just contributing with about 2 %. Dagny 4000/29 EIF = 13 SI 1 KII Em 1 KVI BTEX 7 % Naphthalenes 9 % 2-3 ring PAH 10 % Alifater 42 % 4-ring+ PAH Phenol C0-C3 9 % Phenol C6-C9 Phenol C4-C5 17 % Figure 1: Contribution to EIF for Dagny scenario A1 Classification: Internal Status: Final Expiry date: Page 7 of 9

8 Figure 2 shows, which components are contributing to EIF = 10 in scenario A2. Also here the natural occurring compounds are dominating the contribution to EIF with about 98 %. Main contributor is phenols C4-C5 (25 %) followed by aliphates (18 %) and 2-3 ring PAH (14 %). Added chemicals are just contributing with about 2 %. Dagny 4000/10 EIF = 10 SI 1 KII Em 1 KVI BTEX 1 Alifater 18 % Naphthalenes 13 % Phenol C6-C9 2 % 2-3 ring PAH 14 % Phenol C4-C5 25 % 4-ring+ PAH Phenol C0-C3 13 % Figure 2: Contribution to EIF for Dagny scenario A2 The maximum EIF for Dagny is 13 (scenario A1). This is a low EIF and figure 3 gives an indication how the EIF for Dagny can be evaluated related to EIF values for 2009 for Statoil s existing fields on the Norwegian Continental Shelf (NCS). Classification: Internal Status: Final Expiry date: Page 8 of 9

9 700 EIF 2009, Statoil Norwegian Continental Shelf EIF Statfjord C Gullfaks B Statfjord B Gullfaks A Gullfaks C Statfjord A Veslefrikk Norne Snorre A/Vigdis Glitne Troll C Troll B Brage Heidrun Kristin Dagny Snorre B Grane Oseberg C Sleipner A/Øst Åsgard A Åsgard B Oseberg F Huldra Oseberg Øst Oseberg Sør Visund Sleipner T/Vest Troll A Njord Heimdal Kvitebjørn Figure 3: EIF 2009, Statoil Norwegian Continental Shelf Dagnys contribution to the environmental risk on the NCS is very limited. The impact on the environment is small. 5 References (1) Frost, T. K., Johnsen, S. Torvik, H. and Eide, T.E. (2009). Application of the Environmental Impact Factor (EIF) as a risk management tool to discharges forproduced water on the Norwegian Continental Shelf. NEL Produced Water Workshop Aberdeen, October th (2) Smit, M.G.D, Frost, T.K. and S. Johnsen (2011). Achievements of risk-based produced water management on the Norwegian continental shelf ( ). Integrated Environmental Assessment and Management (IEAM), Society of Environmental Toxicology and Chemistry (SETAC). Classification: Internal Status: Final Expiry date: Page 9 of 9

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