Nord Stream Re-Issue for Client Comments F. Graziosi S. Bergomi D. Pettinelli. Document title. Agreement PO WBS/CTR A03.

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1 Page 1 of 17 Nord Stream 2 Aug 18, Re-Issue for Client Comments F. Graziosi S. Bergomi D. Pettinelli Rev. No. Date Description Prepared Checked Approved Date Approved Saipem Nord Stream 2 Document title Commissioning Philosophy Job Document LF-E Yes No Document Number W EN PRO GEN REP EN 03 Pipeline Discipline Sub- (Department) Discipline Work Location Doc. Type Originator Id. Unifier Rev. No.

2 Rev. 03 Sh. 2 of 17 CONTENTS 1 INTRODUCTION AND SCOPE Introduction Scope of this Document 4 2 DEFINITIONS AND ABBREVIATIONS Definitions Abbreviations 5 3 REFERENCES Codes & Standards Company Documents Contractor Documents Other Documents 6 4 COMMISSIONING METHODS Method 1: Natural gas injection directly into atmospheric pipeline partly filled with nitrogen Method 2: Natural gas injection under pipeline vacuum conditions Method 3: Natural gas pig-assisted injection with nitrogen batch 11 5 CONSIDERATIONS AND METHOD SELECTION 12 6 MAIN REQUIREMENTS Completion of Other Operations Process Requirements Units Requisites for the Field Activities 16 7 REVISION RECORD 17

3 1 INTRODUCTION AND SCOPE 1.1 Introduction Rev. 03 Sh. 3 of 17 The Nord Stream 2 AG pipeline system (NSP2) comprises of two (2) 48 diameter subsea pipelines including onshore facilities. The lines shall extend from the Russian southern coast of the Gulf of Finland to the German coast in Greifswald area, through the Baltic Sea, with no spur lines or intermediate landfalls. The pipeline route will cover a distance of approximately 1200 to 1300 km, depending on final route selection. While routing through the Baltic Sea the pipelines are generally independent from the existing Nord Stream AG pipeline system (NSP1), but they do run in parallel to NSP1 lines for a substantial length. The pipeline route crosses the Territorial Waters (TW) of Russia, Denmark and Germany and runs within the Exclusive Economic Zones (EEZ) of Russia, Finland, Sweden, Denmark and Germany. Figure 1-1 below gives an overview of the routing considered. Figure 1-1: Nord Stream 2 AG pipeline system overview The base case scenario is to install two pipelines, each with a target capacity of 27.5 GSm³/y at reference conditions of 20 C and 1 atm. Nominal capacity of the Nord Stream 2 AG pipeline system is dependent on final route definition and will be defined upon route selection.

4 1.2 Scope of this Document Rev. 03 Sh. 4 of 17 The engineering activities within the contract between Nord Stream 2 AG and SPF are split into two phases: Basic Design Detail Design This document is relevant to the Basic Design phase. Scope of this document is to define the commissioning philosophy required to prepare the pipelines from a state of completed pre-commissioning condition to ready for operation (gas filled to agreed pressure). The present document is prepared assuming that NSP2 is very similar to NSP1 for what concerns design parameters (e.g. pipeline diameter, pipeline length, pipeline roughness, design pressures and temperatures, PTA piping arrangement). Finally, the present document refers to one of the two offshore pipelines, but each description and consideration is also valid for the other offshore pipeline.

5 2 DEFINITIONS AND ABBREVIATIONS 2.1 Definitions Rev. 03 Sh. 5 of 17 Company: Contractor: Nord Stream 2 AG Saipem S.p.A. 2.2 Abbreviations AGA CS DP EEZ GRS GSm³/y HRE IP KP MAIP MAOP MCC NSP1 NSP2 P PTA PTAG PTAR SPF TW v 2 American Gas Association Compressor Station Design Pressure Exclusive Economic Zone Gas Receiving Station Billion Standard Cubic Metres per Year Heating Reducing Equipment Incidental Pressure Kilometre Point Maximum Allowable Incidental Pressure Maximum Allowable Operating Pressure Main Control Centre Nord Stream 1 Pipeline System Nord Stream 2 Pipeline System Pressure Pig Trap Area Pig Trap Area Germany Pig Trap Area Russia Saipem Fano Territorial Waters Gas density multiplied by the square of gas velocity (flow parameter)

6 Rev. 03 Sh. 6 of 17 3 REFERENCES The reference documentation has been subdivided as follows: a) Codes & Standards; b) Company Documents; c) Contractor Documents; d) Other Documents. In case of conflict between the documents listed in this section, priority is given as per the above order. 3.1 Codes & Standards /A1/ DNV OS-F , Rules for Submarine Pipeline Systems Ed /A2/ AGA Report No. XK0101, Purging Principle and Practice, Third Edition, Washington Company Documents /B1/ /B2/ W-EN-ENG-GEN-TNO-800-OPSLLTEN-01 NSP Operations Lessons Learnt W-EN-PRO-GEN-TNO-800-TN0001EN-03, Technical Note Planned Pipeline Blowdown Concept for NSP2 3.3 Contractor Documents /C1/ W-EN-PROGEN-REP EN, Pipeline Blow-down Philosophy /C2/ W-EN-ENG-GEN-REP EN, Design Basis (Basic Design) /C3/ W-EN-PRO-GEN-REP EN, Operating and Safeguarding Philosophy /C4/ W-EN-PRO-GEN-REP EN, Pipeline Safety Process Philosophy /C5/ W-EN-CSC-GEN-REP EN, Safety Instrumented Systems Philosophy 3.4 Other Documents /D1/ 804-MPR-MOM , Nord Stream 2 Project Design Engineering Technical Start-up Meeting /D2/ G-EN-PIE-REP D, Nord Stream Project Commissioning Criteria and Philosophy /D3/ Handbook of natural Gas Engineering. McGraw-Hill, New York /D4/ N-EN-PIE-REP-000-PHILBDES, Next Basic Design Philosophy /D5/ N-EN-PIE-REP-000-FSDES001-A, Next Design Basis for Basic Design Phase /D6/ 2-CM-GAS-REP-000-GASFILLE-00, Nord Stream Project Pipeline 2 Gas Filling Close Out Report /D7/ Oil & Gas Journal Oct. 7, 2013, Nord Stream dry air purge improves nitrogenslug use

7 4 COMMISSIONING METHODS Rev. 03 Sh. 7 of 17 The commissioning is a one-off operation which is carried out after the completion of pre-commissioning to fill and pressurise the pipeline system with natural gas up to the agreed pressure so that it can start transporting natural gas. The commissioning activity actually includes all operational steps necessary to bring the pipelines from the completion of the pre-commissioning status up to the ready for operation status. The beginning of commissioning operation typically coincides with the hand-over from Construction to Operations. Before the commissioning operation, the pipeline system is as left after the precommissioning operation, therefore it is assumed that the pipelines are completely installed, tied to the terminal facilities, tested and prepared to receive and transport the natural gas according to the defined specifications. Since, at the end of pre-commissioning, the pipeline is typically filled with dry air close to atmospheric pressure, the main criticality of commissioning operation is represented by the necessity to inject natural gas into an almost-atmospheric pipeline without the risk of formation of explosive or flammable mixtures inside the pipeline (due to the contact between the air and the natural gas). The formation of explosive or flammable mixtures inside the pipeline can be avoided by: Injecting an inert gas (e.g. nitrogen) into the pipeline before the natural gas, in order to displace the air from the pipeline before the arrival of natural gas. Injecting the natural gas into the pipeline under vacuum conditions (below a minimum pressure value, the contact between air and natural gas does not form explosive or flammable mixtures). Using physical barriers (e.g. pigs) to separate the natural gas from the air. These general criteria (to avoid the formation of explosive or flammable mixture inside the pipeline) lead to the following possible methods for natural gas injection into the pipeline during the commissioning operation: 1. Natural gas injection directly into the almost-atmospheric pipeline, partly filled with nitrogen. 2. Natural gas injection under pipeline vacuum conditions. 3. Natural gas injection as propellant of a pig train confining a nitrogen batch.

8 Rev. 03 Sh. 8 of Method 1: Natural gas injection directly into atmospheric pipeline partly filled with nitrogen This method consists of the displacement of dry air from the almost-atmospheric pipeline by means of the injection of natural gas preceded by a batch of nitrogen (inert gas) without any physical barrier (pigs) between gases. The contact between the natural gas and the air is prevented by the nitrogen batch which acts as a local barrier. Nitrogen purity for this operation is required to be better than 99%. During the gas flow through the pipeline, a certain mixing between the involved gases is expected at the interface between natural gas and nitrogen and at the interface between nitrogen and air, as an effect of the natural diffusion between gases, promoted by their different molar densities. Therefore the interfaces between gases (natural gas/nitrogen and nitrogen/air) will not remain perfectly defined. The mixing between gases has to be limited as much as possible in order to: Minimise the nitrogen amount which is necessary as barrier to avoid the contact between natural gas and air. Minimize the volume of natural gas mixed with nitrogen, because it represents a loss of natural gas. When the nitrogen content inside the natural gas exceeds the limits of the quality specification, the natural gas cannot be exported to GRS but it must be discharged to atmosphere. According to the literature, the gas mixing at the interfaces is promoted by the laminar flow regime (i.e. low velocity) because of the gases stratification. If the gas velocity is kept above a minimum value to avoid the laminar flow regime (the minimum value of 1.83 m s -1 is recommended for gas velocity by AGA, see Ref. /A2/ and Ref. /D7/), the longitudinal mixing zone is limited. During the commissioning of the Pipeline 2 of NSP1, the gas velocity was averagely maintained at 4.2 m s -1 (Ref. /D7/). With this velocity, the air/nitrogen mixing zone was 1.5 km (very small), whilst the maximum size of the nitrogen/natural gas mixing zone was 4.6 km (Ref. /D6/ and Ref. /D7/). A nitrogen batch of 120 km was injected into the Pipeline 2 of NSP1 at atmospheric pressure, immediately prior to start the natural gas injection. This nitrogen amount can be considered safe on the basis of the good experience of NSP1 (Ref. /D6/ and Ref. /D7/). The system used to introduce the nitrogen into the pipeline has to be selected taking into account: Logistic requirements (availability of nitrogen amount, availability of CS). As much flexibility as possible in order to respect to scheduling of the final gas filling operation (nitrogen filling also from GRS). Duration of operation. Firstly air, then nitrogen and finally a mixture of nitrogen and natural gas will be vented to atmosphere through the vent stack installed at the PTAG for the pipeline blowdown (Ref. /C1/). The nitrogen/natural gas interface will be monitored using a temporary gas

9 Rev. 03 Sh. 9 of 17 chromatograph installed on the vent lines: when the nitrogen is completely replaced by the natural gas (i.e. the natural gas matches the acceptance criteria, verified by means of the gas chromatograph), the valves at the PTAG are closed and the offshore pipeline can be pressurised with natural up to the agreed pressure. During the commissioning of the Pipeline 2 of NSP1, 3.5 days were approximately taken to displace air and nitrogen from the offshore pipeline. After this time, the vent discharge system in Germany was closed and the filling of the offshore pipeline with natural gas was started. After approximately 19 days the overall gas filling operation was completed (Ref. /D6/ and Ref. /D7/). 4.2 Method 2: Natural gas injection under pipeline vacuum conditions This method for natural gas injection into the pipeline is based on the vacuumization of the offshore pipeline. The influence of pressure on the flammability limits is showed in Figure 4-1 drawn from Ref. /D3/. At low pressures, i.e. 67 mbar (0.97 psi) (i.e. vacuum conditions), natural gas air mixtures are not combustible. Figure 4-1: Effect of pressure on limits of flammability of natural gas mixture Starting from pipeline in stand-by and filled with dry air at atmospheric pressure, the operation consists of a forced depressurisation by vacuum pump systems located both at CS and GRS. Forced depressurisation is ended when the maximum pressure along the pipeline, i.e. at the deepest sea bed locations, reaches the value around 60 mbar (0.87 psi).

10 Rev. 03 Sh. 10 of 17 According to the flammability limits under vacuum conditions, it could be possible to inject natural gas into the pipeline without any risk of ignition, provided that, during the gas injection, vacuum conditions are maintained at the interface front all along the pipeline. Due to the very small amount of air content, it is wise to displace in part or totally this residual air by nitrogen, in order to avoid any possible formation of natural gas-air mixture. Therefore, a preliminary nitrogen injection is usually envisaged at a controlled flow rate to maintain the ultimate pressure profile reached along the pipeline at the end of depressurisation. Vacuum pump systems at GRS remain in operation throughout nitrogen injection. Gas injection from CS may follow immediately with the same flow rate of nitrogen and with vacuum pump systems in operation up to the complete evacuation of dry air from the pipeline. The oxygen content of the pipeline exhaust at the vacuum pump systems is monitored by using an oxygen analyser probe. Once the air is completely displaced and pipeline is only filled by nitrogen and natural gas, the vacuum pump systems may be shut-down and the pipeline may start to be first pressurised up to the agreed pressure. As an alternative, the pipeline may be only-partially filled with low pressure nitrogen and the natural gas may be injected behind a batch of nitrogen. The vacuum pumps have to be kept running until nitrogen is detected at GRS. This alternative further reduces the nitrogen consumption.

11 Rev. 03 Sh. 11 of Method 3: Natural gas pig-assisted injection with nitrogen batch This method consists of the displacement of dry air by means of the injection of natural gas assisted by an interface train of at least 2 pigs enclosing a batch of nitrogen to prevent any mixing of air and natural gas. The pigs act as a physical barrier between natural gas and air. The run of pigs along the pipeline requires a minimum back-pressure in front of the pig train in order to adequately control the pig velocity and minimising the pig velocity oscillations. Excessive oscillations of the pig velocity may actually cause the corruption of seals with possible loss of one or more pigs along the pipeline. This risk could be mitigated increasing the back-pressure in front of the pig train (typically 12 to 15 bara). This means that the pipeline needs to be partially pressurised before starting the air displacement. In order to preserve the pig structural integrity, the pig velocity is required to be limited below a defined maximum value (specified by vendors). This constraint may become particularly restrictive due to the length of the Nord Stream 2 pipelines. Taking as reference the experience of some vendors, a likely value for the maximum allowable pig velocity is about 4 m s -1. With this method, the operational sequence for natural gas injection can be summarized as follows: Pressurizing of the pipeline with dry air to approx bara. Preliminary flowing of a limited quantity of nitrogen in the pipeline (about 1% of geometric volume of the pipeline); this operation is done with discharge of air to atmosphere at PTAG. Launching of the first separation pig. Injecting of a nitrogen batch into the pipeline, with a suitable volume to be sized in order to avoid any risk of natural gas-air mixture formation. Launching of the second separation pig (same type of the first one). Flowing of the natural gas, controlling the flowrate from CS, with a continuous monitoring of pressure at both pipeline ends (PTAR and PTAG), in order to detect possible increases of pressure drops along the pipeline, ascribable to the undesired stoppage of pig train. During this operation, the air and the nitrogen arriving at PTAG are released to atmosphere through the vent stack installed at the PTAG for the pipeline blowdown (Ref. /C1/). Once the second pig is received at PTAG pig trap, the offshore pipeline can be pressurised with natural gas up to the agreed pressure.

12 Rev. 03 Sh. 12 of 17 5 CONSIDERATIONS AND METHOD SELECTION The philosophy for the pipeline commissioning is conceived with the purpose to: Minimise the duration of the operations. Use of conventional or standard equipment. Minimise the temporary pipeworks. Maximise the safety of the operations. Take care of risk of possible abort and operation restart. Minimise environment impact. Minimise consumable materials. Avoid any possible contingency event (e.g. hydrate formation). Ensure safe discharge during the filling with natural gas. The peculiarities of the commissioning methods described in 4 can be summarised as follows: The Method 1 (natural gas injection directly into atmospheric pipeline partly filled with nitrogen) is characterized by limited discharge of nitrogen and natural gas to the atmosphere. It is cost effective (minimum equipment required), it is fast and simple and does not require the use of pigs. The Method 2 (natural gas injection under pipeline vacuum conditions) is characterized by the highest safety level (compared to other methods) and the smallest nitrogen consumption. No particular risks are envisaged in case of accidental interruption of the operations, because, in that case, it is sufficient to close both the inlet and the outlet points of the pipeline to maintain the achieved vacuum level. On the other hand, this method requires the vacuumization of the entire offshore pipeline and the availability of proper equipment. The Method 3 (natural gas pig-assisted injection with nitrogen batch) is characterized by limited discharge of nitrogen and natural gas to the atmosphere, but it requires the use of pigs with the relevant drawbacks related to: o The need to control and monitor pig velocity all over pig travel along the pipeline (flow control). o The possible occurrence of pig stuck. Temporary interruption of the operations should be avoided. Due to cost effectiveness, quickness, simplicity and to the good experience with the commissioning of Pipeline 2 of NSP1 (Ref. /D2/, Ref. /D6/ and Ref. /D7/), the Method 1 is selected for the commissioning of the offshore pipelines of NSP2.

13 Rev. 03 Sh. 13 of 17 6 MAIN REQUIREMENTS This section describes the main requirements for pipeline commissioning in terms of: Completion of other operations. Process requirements. Units. Requisites for field activities. 6.1 Completion of Other Operations The commissioning of the offshore pipeline can be started only after the verification of the completion of some other operations. In particular: The pre-commissioning operation of the offshore pipeline has to be successfully concluded and certified: the offshore pipeline is expected to be filled with dry air close to atmospheric pressure. All pre-commissioning and commissioning operations at PTA have to be completed. Both PTAR and PTAG have to be definitely connected to the offshore pipeline, tested and ready for operations. In particular, the availability of the pipeline blow-down system at PTA is considered strictly necessary for the commissioning operation, because the pipeline blow-down system will be used for the air displacement from the offshore pipeline to the atmosphere. The completion of pre-commissioning and commissioning activities at CS and GRS is not strictly required, because the offshore pipeline can be also commissioned without making use of the CS and GRS facilities. If these two stations are available, they can be involved in the commissioning operation of the offshore pipeline, to import (from CS) the natural gas for offshore pipeline filling and to immediately start natural gas export (to GRS), once the offshore pipeline reached the agreed pressure (commissioning completed). If these two stations are not available, the natural gas can be directly imported from the onshore pipeline network upstream the CS (temporary units are needed for natural gas dehydration, heating and pressure reduction; see 6.3), whilst the export of natural gas to GRS can be delayed until the completion of pre-commissioning and commissioning operations of GRS.

14 Rev. 03 Sh. 14 of Process Requirements The pipeline commissioning requires the availability of natural gas at suitable conditions to allow the gas injection into the pipeline at atmospheric pressure, in compliance with design and operative limits described in Ref. /C2/ and /C3/. To this purpose, the natural gas is required to be provided within the composition limits and with suitable pressure and temperature to allow the gas injection into the pipeline at atmospheric pressure in compliance with the design temperatures Gas Quality The gas quality is an important parameter which needs to be continuously monitored during the pipeline commissioning with the purpose to avoid the off-spec gas. After the completion of pipeline commissioning, the NSP2 actually has to be ready to immediately start the transport and the delivery to GRS of natural gas within the composition limits specified in Ref. /C2/ and Ref. /C3/ (on-spec gas). The composition limits also include the specification for the water content. The water content inside the natural gas must comply with the specification (Ref. /C2/ and Ref. /C3/), in order to avoid condensation of liquid water inside the offshore pipeline with possible concerns for corrosion and hydrate formation. To this purpose, the natural gas needs to flow through a dehydration unit for water content control prior to the injection into the offshore pipeline. On-spec gas must be available at NSP2 entrance Pressure and Temperature Since, prior to starting the pipeline commissioning, the offshore pipeline is at a pressure close to the atmospheric value, whilst the natural gas is typically available from the onshore facilities (CS or Russian domestic grid) at a pressure significantly higher than atmospheric, the natural gas has to be injected into the offshore pipeline through a control valve which allows the regulation of the pressure gap between the source of natural gas and the offshore pipeline. The expansion of the natural gas through the control valve is expected to lead to very low temperatures inside the offshore pipeline (gas cooling by expansion), especially if the temperature of gas upstream the control valve is already quite low. The low temperatures inside the offshore pipeline can be avoided by adequately heating the natural gas prior to expending it through the control valve. The gas heating upstream the control valve actually allows compensating the subsequent gas cooling across the control valve.

15 Rev. 03 Sh. 15 of Units In order to have natural gas at suitable conditions to allow the gas injection into the pipeline at atmospheric pressure (as required in 6.2), the following main units are necessary: Gas dehydration unit. Unit for gas pressure and temperature regulation. If the CS is ready in time for pipeline commissioning and is provided with a control valve and a system to heat the natural gas (upstream the control valve), the CS might be used to dehydrate the natural gas and regulate its pressure and temperature prior to the injection into the offshore pipeline. If the CS is ready in time for pipeline commissioning but it is not provided with control valves and systems to heat the natural gas (upstream the control valves), the CS might be used to dehydrate the natural gas, but not to regulate its pressure and temperature prior to the injection into the offshore pipeline. A heating and reducing equipment (HRE) is consequently necessary to: Reduce and control the pressure of natural gas by means of control valve(s). Heat the natural gas before pressure reduction, in order to counterbalance the gas cooling by expansion and keep gas temperature above the minimum design temperature. Meter and keep the required gas velocity throughout the commissioning operation. The HRE may be installed in the CS area or in the PTAR. If the CS is not ready in time for pipeline commissioning, in addition to the HRE, there is also the need of a temporary unit to dehydrate (and remove the impurities from) the natural gas prior to the injection into the pipeline. This temporary unit was used for the commissioning of the first pipeline of NSP1: it was called HAFI and was outside NSP2 battery limits. Three scenarios may be identified according to the characteristics and the availability of the CS: 1. The CS is ready (dehydrated gas is available) and is used to regulate gas pressure and temperature. 2. The CS is ready (dehydrated gas is available), but gas pressure and temperature are regulated in the temporary skid mounted HRE (heating and reducing equipment). 3. The CS is not ready and it is by-passed. Gas is directly taken from the Russian domestic grid (upstream the CS) and temporary units are necessary to dehydrate the gas and to regulate its pressure and temperature.

16 Rev. 03 Sh. 16 of Requisites for the Field Activities The main requisites for field activities may be summarised as follows: Prior to start the pipeline commissioning, it is essential to isolate the battery limits of the offshore pipeline from the rest of the transport system either by mechanical means or by severing all of the connections. Two distinct but related objectives are thus accomplished (Ref. /A2/): o Preventing any gases (natural gas, insert gas or air) from leaking out during the operation. o Preventing any gases from leaking in after the operation, when the transport system is out of service for inspection, repair or demolition. Isolations should be finally tested and certificated. All the critical parameters shall be monitored and recorded for the whole duration of the pipeline commissioning in order to verify the correct execution of the operations. Adequate communications protocol shall be established among PTA, MCC and CS/GRS (if involved in the pipeline commissioning) in order to: o Ensure the correct coordination of the operations during the pipeline commissioning. o Improve the control and the monitoring of the critical parameters during the pipeline commissioning. The selection of personnel to perform the pipeline commissioning represents another important requisite (Ref. /A2/): the person assigned to the responsibility of directing the pipeline commissioning should have had previous experience, be technically competent and possess requisite authority. The number of persons required to control the pipeline commissioning will vary depending on complexity and magnitude of the operations. In case the commissioning requires an extended period, provisions should be made for relief personnel. The duties of those assigned to the purging operation may include (Ref. /A2/): o Arranging for adequate supply of the purging gas to be used. o Controlling of the flow of the gas and adequately of the venting of the purged gas. o Testing the quality of the delivered gas. o Establishing reliable communications. o Notifying the public where necessary.

17 Rev. 03 Sh. 17 of 17 7 REVISION RECORD Re-Issue for Client Comments: Revised according to Client comments W-EN-PRO-GEN- CMM EN-02.1 Revised according to Client clarifications/instructions agreed during the January 2016 Monthly Meeting (see MoM number EN-PRM-GEN-MOM ). Acronyms and definition aligned to W-PJ-DCC-GEN-FOR EN-05. F. Graziosi S. Bergomi D. Pettinelli Issue for Client Comments F. Graziosi S. Bergomi D. Pettinelli Issue for Internal Discipline Check F. Graziosi S. Bergomi D. Pettinelli Rev. No. Date Description Prepared Checked Approved Date Approved Saipem Nord Stream 2