LESSONS LEARNED FROM THE COMMISSIONING, START-UP AND THE OPERATIONAL PHASE OF A SUBSEA PIPELINE

by

Ad Pijnacker Hordijk (Project Manager Large Projects, NV Nederlandse Gasunie)

Rein Bolt (Technical Manager BBL Company V.O.F.) Keywords: strategic infrastructure, offshore pipeline, commissioning & start-up,

operational issues. 1. INTRODUCTION In December 2006, after a construction period of 2.5 years, a dedicated Project Team successfully completed the construction of the 235 km subsea BBL pipeline and handed over the pipeline and facilities to the pipeline operator. BBL is an acronym for Balgzand (the Netherlands) Bacton (the United Kingdom) pipeLine. The pipeline has been in commercial operation since 1 December 2006.

The BBL pipeline system consisting of a compressor station in NL, an on- and offshore pipeline (NL+UK) and landing facilities in UK is owned by BBL Company V.O.F., which company is a partnership between Gasunie BBL B.V. (60%), Fluxys BBL B.V. (20%) and E.ON Ruhrgas BBL B.V. (20%). 2. OBJECTIVES This paper describes the organisation and challenges during the commissioning and start-up phase in order to successfully hand-over responsibility to the operational phase team. The major operational experiences during the first year of operation will also be addressed. Due to the fact that the dedicated Project Team and contractors “disappear” after the operational handover, the remaining teething troubles had to be analysed and solved by the operator. One of the lessons learned was that these challenges could be avoided, if there was a closer cooperation between the Project Team and the operator during the last phase of the construction and the handover to the operator. The project involving the construction of all BBL assets was divided into three different specific parts. These parts were:

• A new compressor station with electrically driven compressors in the Netherlands at Anna Paulowna (Balgzand area);

• The offshore pipeline from Anna Paulowna up to the United Kingdom (Uk) at Bacton consisting of an onshore pipeline including dune crossing, a valve station just before the dune crossing and an offshore pipeline to Bacton including 2 cofferdams;

• A gas-treating station in Bacton in order to filter, heat, measure and control the gas flow before it is delivered to the adjacent network operator.

3. ORGANISATION Many companies have been and are still involved in the construction, commissioning and start-up and operation of the BBL pipeline system from the Netherlands towards the United Kingdom. The gas is transported from the Gasunie grid in the northern part of Holland by compressor owned by BBL Company VOF towards the Uk where the gas is warmed up, measured and flow control by Shell as the operator and transported towards National Grid as the shipper in the Uk. The overall project was divided into the 3 previously mentioned parts, see figure 1b, each consisting of a separate engineering and construction team. These teams were to hand over the pre-commissioned functionality of the given parts to the overall commissioning and start-up team.

Figure 1b : Project geographic’s

Figure 1a : BBL geographic’s

As often in multidisciplinary projects, the last activity is under time pressure, due to delays in the previous activities. This means that it is of the utmost importance that the procedures and methodologies used by the commissioning and start-up teams are well prepared and are not jeopardized by any unforeseen delay. Since the end date was not allowed to be shifted by even one minute, due to huge financial penalties that were included in the contracts with shippers, it was in everybody’s interests to succeed in continuous gas transportation from 1 December 2006 at 06:00 GMT onwards!

The project was organised in such a way that BBL Company V.O.F., as owner of the assets, received the keys of the project (a turn key project) at the handover date. The project team, under the overall responsibility of the Project Executive, was divided into separate project responsibilities for construction and for commissioning and start-up. Moreover the commissioning and start-up preparations started more than one and a half years before the actual finishing date. In this respect, there were 2 official handover ceremonies for the three above-mentioned parts. 4. METHODOLOGY 4.1 Common This paper will focus more on the details of the commissioning and start-up and the following activities during the first year of operation than on the construction activities. First of all, a commissioning project plan was derived and a commissioning team was put together. Since it was very clear from the beginning that the commissioning would be under enormous time pressure, a very detailed plan was generated and verified by internal and external experts. Furthermore the plan was discussed with all parties involved in the overall project, in order to get acquainted with the interfaces and expectations of individual key persons and contractors responsible. The commissioning team also prepared a risk register for all the actual activities

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during a number of commissioning workshops. The risks (~ 100 items) were prioritized by probability times consequences in a range of 1-25 and further divided over Turn Over System (TOS) numbers and categories such as business risk, HSE danger and the risk of concurrent activities. The team also initiated mitigation measures for all the high and medium priority risks and even for a number of low priority risks as well. The Risk Register not only increases the confidence of supervisors and principal, but also provides more insight into the controllability of the work to be carried out. A test plan was developed according to the V-shaped model as indicated in figure 3. The idea is that the verification and dynamic testing process on the right hand side of the V will be executed against the engineering, procurement and construction (EPC) process on the left hand side. This is one of the reasons that commissioning should be involved during the EPC part of the project. The test methodology as indicated in figure 3 will be completed with the specific standards and norms on the left hand side of the V-model and the procedures and standard test requirements that are applicable for each of the indicated balloons along the V-model line in order to get a fully accepted and verified system. A specific model was drawn especially for installation, in order to achieve full understanding by all parties. Normally construction or EPC contractors are working according the construction-driven or discipline-driven schedule. This means that items will be finished, delivered and handed over according to the schedule of their discipline contractors and subcontractors. Due to the fact that the achievement of the contracted finish

date was under extreme pressure, the relationship between construction contractor and commissioning team was changed into a so called ‘commissioning-driven’ schedule relationship. This meant that the items that were needed first were also constructed, delivered and handed over first according to the commissioning plan. In order to be able to know which item should be scheduled first and which last, one needed to know upfront how to execute the commissioning. Obviously the schedule which allowed for the fastest and most efficient commissioning was selected. One can distinguish between the commissioning of different systems, clusters or loops as indicated in figure 4. In the BBL project, we chose to execute the commissioning work by means of a Turn Over System (TOS). Each TOS has a number of loops. In total 44 TOS ’s were identified and over a thousand loops were established. All

information regarding equipment, each loop including associated test certificates, calibration procedure, other inspection dossiers and the commissioning activities were inputted into the Windows Project Completion System (WinPCS). This system, which was already in use by the construction contractor, was further enlarged and used by the commissioning team to keep easily track of the progress of the work and also to pay immediate attention to the remaining scope of the work, the next week work front and the non-agreed items. These items were divided over three categories in order to provide the team with the opportunity for controlling the work front with the highest priority items. Due to the tight timeframe of the commissioning, it now became possible to overlap construction and commissioning activities and not to wait to start commissioning until the last construction activity had been handed over from construction to commissioning. 4.2 Commissioning of the pipeline During handover, the commissioning team responsible for the onshore and offshore pipeline received a pipeline from the construction team which had just been successfully hydrostatically tested on both sides. The pipeline was connected to the rest of the pipeline system with golden welds. To be able to carry out the golden welds, the pressure of the strength test was released and the parts where the golden welds were executed were totally free of sea water. This meant that the hydrostatic pressure was off the system and some air locks were in the system due to the golden welds. The activities that were carried out during commissioning and start-up :

• Further dewatering; • Drying and depressurizing; • Purging valve cavities and barred T; • Nitrogen filling and venting;

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• Pressurizing, initial gas fill and first gas flow; The challenges arising during these activities which will be discussed in more detail were :

• Salinity since the hydrostatic strength test was carried out with sea water; • Hydrocarbons at a process area which is still under construction; • Dispersion and venting; • Water dew point of the gas during first gas flow; • Continuous gas flow at handover date;

4.2.1 Overview Early in the project, the commissioning team started to investigate literature and previous commissioning experiences especially relating to the North Sea. Based upon that knowledge, a tender document was established and put on the European market as a request for quotations. During the evaluation of the bid documents, the most effective commissioning method was discussed with the bidders. The construction contractor for the onshore pipeline decided to perform a hydrostatic strength test on the pipeline with water coming from the Noord Holland canal, whereas the construction contractor for the offshore pipeline decided to use filtered, but extreme salt seawater instead of the sweet water of the Noord Holland canal. These basic starting points meant that the method plan also needed to be developed regarding how to get rid of the salt deposits in the pipeline. After the commissioning contractor had undergone extensive selection procedures, all these items, drying method, salinity, air pockets, HSE and QA/QC points were discussed and put into the

contractor’s method plan. The estimated drying time, water dew point criterion, number of runs, number of trains versus volumes of water between cleaning pigs, overall schedule and confidence probabilities were calculated or estimated upfront. Then the plan was discussed with project staff, the Shell project team responsible for the engineering, construction and commissioning of the receiver station in Bacton as well as the Shell plant management responsible for the operational health and safety at the Bacton plant. A few challenges needed to be added to the pipeline constructor’s method plan. These items were safety, dispersion of gas and nitrogen, cleaning of the barred tee and valve cavities, noise contours, working hours, demonstration of cleanliness and environmental issues. Besides a lot of meetings with all the staff involved, alignment sessions were carried out to harmonise the approach and goals of the pipeline commissioning. The commissioning team was fortunate in having the opportunity of a feedback meeting with experienced staff from Statoil in Stavanger. The plan was presented and discussed, however major changes in the pig train were proposed by Statoil. Their experts came up with the idea of getting rid of the two separation pigs between the air, nitrogen and gas volumes. A pig in the very dry air slots could easily ignite the bone dry air leading to undesirable consequences, such as a fire and all kinds of subsequent damage to the inner and outer side of the pipeline. Taking the proposal into account, the team encountered another challenge that had to be resolved. The dispersion of two different gases along the 235 km of pipeline had to be calculated and dealt with on site. Gasunie onshore pipelines in the Netherlands are normally filled directly with gas, not having nitrogen to separate the air from the gas. By changing the philosophy, adding nitrogen as a means of separation and propelling the nitrogen slot without high seal BiDi pigs, the commissioning of the BBL pipeline was different compared, for instance, to the IUK pipeline, which was commissioned in 1998. 4.2.2 Dewatering The dewatering actually started just before the golden welds had to be welded. There were golden welds at the Bacton cliffs and at the valve station Julianadorp. By removing the test heads at either side a lot of water (and pressure) was removed from the pipeline straight away. However, after handover from construction to commissioning, salty sea water was still present in the pipeline. Which part of the pipeline was filled with which type of water and for how long was calculated well before the start of the pipeline commissioning. Since the period during which water was in those parts was quite short, less than one month at least, the team took the decision after one of the contractor alignment sessions not to use a corrosion inhibiter. One of the positive results was that the permit for the dewatering could be obtained much more quickly. As there

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were different types of water in the various parts of the onshore and offshore pipeline, the following points were determined at an early stage in the project and discussed with all the relevant people :

• Number of cleaning runs; • Number of trains versus volumes of

fresh water; • Estimated drying time within P90

confidence limits; • Number of compressors to propel

the pigs with: o availability and redundancy; o noise (24hr operation); o permits;

• Heating possibilities • Calibration of sensors • Risk mitigating measures

The team decided to have one run with a pig train consisting of 10 pigs. This pig train was propelled by oil-free, dry compressed air and was specially designed to :

• Dewater the pipeline; • Remove the salt deposits from the pipeline wall; • Swab the pipeline with dewatering pigs;

Figure 7 : pig train overview and direction <==

Most of the sea water was moved away by the first high seal BiDi pig. The Gasunie laboratory calculated that, by having 4 slots of fresh water to dilute the salt sea water from the pipe wall, the salt content would be ultimately less than 1000 ppm, which is a reasonably acceptable value. This is of course dependent on the assumed parameters such as amount of fresh water, film layer at pipe wall, slippage of water along the high seal pigs etc. The salt content is expressed in Total Dissolved Solids (TDS). The salt contents of the various slots were measured before entering into the pipeline. The fresh water coming from the Noord Holland Canal had a value of 400-600 ppm which, (compared to the salty sea water, ± 35.000 ppm) is considered to be sweet water. The slots put into the pipeline at Anna Paulowna came from the installation’s potable drinking water system and was filtered up to 50µm. After removing the pigs from the pig trap at Bacton, the salt content was measured again. The salt contents were:

• Fresh water slot between pig 1 and 2 957 ppm • Fresh water slot between pig 2 and 3 594 ppm • Fresh water slot between pig 3 and 4 363 ppm

Since the pipeline from Julianadorp up to Anna Paulowna was hydrostatically tested with almost fresh water from the Noord Holland Canal there was already a slot of fresh water in the pipeline of 4km. In order to save the fresh water at Juliandorp, a high seal BiDi pig was introduced into the pipeline at the valve station just before the dune tie-in and golden welds were completed. All the other pigs were introduced into the pipeline system via the pig trap receiver in Anna Paulowna, see also figure 5. The pig train started with 3 high seal BiDi pigs separating 4 slots of fresh water. Valves were opened in Julianadorp to get rid of potential air pockets. The 4th pig in sequence was an Electronic Calliper Pig (ECP), which will be discussed in a later paragraph. Then another 6 high seal BiDi pigs followed to separate the bone-dry air slots, as can be seen from figure 7. The dewatering and cleaning train was started on 27 September 2006 and finished on 25 October, when the last pig was received at Bacton 4.2.3 Cleaning The team decided that there should be only one cleaning run with 10 BiDi pigs and different slots of fresh water and dry air instead of various runs, because of the time pressure. There was also mutual agreement for using only one direction for the pigs, namely from Anna Paulowna (NL) towards Bacton (UK). Since the

Seawater 4km H20 H20 400m3 H20 400m3 H20 400m3 500m AIR 500m AIR 500m AIR 500m AIR 500m AIR 500m AIR Line Vol AIR

Offshore VS Julianadorp 3 Highseal BiDi pigs at CS Anna Paulowna ECP pig ---------------------------------------------- 6 Highseal BiDi pigs at Anna Paulowna -------------------------------------------

Figure 6 : different pipeline sections

offshore pipeline was full of salty sea water it was upfront calculated how many volumes of fresh water one would need to get a clean pipeline . All valve cavities and the barred-T at Bacton were also cleaned by means of flushing. The barred T was even inspected with a borroscope in order to prevent any dirt in the gas receiving installation at Bacton. 4.2.4 Drying and depressurization The pipeline was further dried with oil-free compressed air. The drying started on 26 October and was finished on 31 October, less than one week later, with an exiting air dew point of -33ºC at atmospheric pressure, see figure 8. The pipeline was continuously dried with air dryer than -40ºC with an injection flow of approximately 15,000 Sm³/hr. The short drying time was due to :

• The rapid pipeline depressurization after dewatering. bleeding off at high speeds removed water from the pipeline and/or dissipated residual water from the pipeline wall;

• The quick depressurisation with the use of flow control valve and air silencer at the receiving end during the continuous high volume, low pressure, dry air purge;

4.2.5 Calliper pig One of the pigs dividing the fresh water slot and dry air was the Electronic Calliper Pig (ECP). The ECP was ordered because the pipeline also would have an intelligent pig run by means of a MFL-pig at a later stage. In order to save time for a separate verification pigrun, the team decided to have the ECP-pig as a verification tool of the pipeline inner diameter in the train of pigs necessary for the drying process. The MFL pigrun and consequently the ECP pig was ordered with another company. Unfortunately the coupling in the ECP-pig broke after a few kilometres whereas no information was gathered due to a malfunction in the defected sensors. It was found out that the coupling broke because of a flaw in the security device of the coupling and the variations in (acceleration) speed of the pig train as a result of air pockets and difference in medium (water versus air) over the ECP-pig. 4.2.6 N2 filling After the pipeline was depressurized, it was filled with a (large) slot of nitrogen of almost 50,000 Sm³. The nitrogen was injected over a period of 2 days. The nitrogen acted as an inert interface between the bone-dry air and the natural gas full of ignitable hydrocarbons.

4.2.7 Gas pressurizing Since the pipeline commissioning team was very successful and the compressors at Anna Paulowna were not even commissioned at that time, the team decided to make use of a short cut from the measuring station directly into the scraper trap. This extra, temporary, aboveground pipeline was installed by the Gasunie Special Department executing stopple and split-T operations at full pressure, troubleshooting calamities and incidents at full gas outflow. Heaters from the pipeline commissioning contractor were used to heat up the gas to a minimum of +20 ºC. Since filling up the pipeline at once was not commercially viable due to specific shipper contracts, filling up at a speed of 2.5 m/s was planned. It was strongly recommended that the project team should not make use of BiDi pigs between the bone-dry air and the nitrogen. The reason for this was that the friction of the pig with the pipeline wall could ignite the bone-dry air with all kind of consequences. Therefore the basic approach eliminated the pig between the nitrogen and gas . As a result of that, the dispersion of air and nitrogen and, moreover, the nitrogen and gas, had to be calculated at various (driving) speeds and parameters, see figure 9. Using a back pressure controller specifically installed at Bacton for that reason, avoided the compression of the nitrogen slot and the amount of nitrogen was about a third of the total length of the BBL pipeline. Purging the nitrogen slot at high speed also helped minimise the mixing of nitrogen and gas, resulting in maintaining the integrity of the inert nitrogen slot. The spread of the dispersion of gas and nitrogen was also calculated upfront in order to know precisely when the

Bone dry air ~75 km N2 Natural gas

Figure 8 : drying temperature vs time

Figure 9 : gas dispersion

back pressure controller (towards air) had to be closed. As soon as these high concentrations of hydrocarbon gas were measured upon discharge from the temporary silencers at Bacton, the pipeline was filled with gas and the venting system was closed. First of all the system was pressurized up to 8.8 bar on 8 October 2006. 4.3 Commissioning of the compressor station The commissioning of the compressor station was carried out by Gasunie personnel with the help of several contractors. Normally and certainly in former times, the construction of an installation was handed over after the construction was completely finished. The construction of Anna Paulowna was outsourced to an EPC

contractor. Due to the time pressure to finish well before the contractual gas transporting date, commissioning activities had to start during the construction phase itself, as shown in figure 10. It was also preferable to hand over the construction to the commissioning team in the order that was determined by the commissioning team as the most effective and efficient one. For instance, the safeguarding systems and the earthing system were the first to be handed over. 44 turnover systems were identified containing many different disciplines. The commissioning team had just started their work while the EPC contractor had already almost

finished the engineering part. Due to the time pressure, we would have liked a commissioning-driven construction. But in practice that was not really possible anymore due to agreed procurement and construction schedules. After several meetings and discussions with the construction contractor, the commissioning team was able to generate a flawless start-up plan, as shown in figure 11, based upon the previously discussed handover system and the construction contractor’s work front. Since during the commissioning, the plant was powered up and was pressurized with natural gas a bit later, the formal handover from construction to commissioning also had to be initiated from a point of view of security, health, safety and environment. More than a thousand loops were verified, checked and put into operation while the construction was carried out in parallel. This was made possible by several useful alignment sessions that were organised at an early stage by the Project Executive for all contractors on site. It goes well beyond the aim of this paper to describe all the turnover systems in detail. It is clear that many people have worked long hours to reach the ultimate goal of transporting gas to the UK before 1 December 2006. The commissioning of the compressor station encountered challenges during the commissioning time. These challenges were:

• The emergency no-break system had an unknown problem in the synchronisation software, and the coupling between motor and generator did break while performing an ESD test on the system. The incident was solved a long time before the operational date;

• The compressor units were ordered as a “carbon copy” of a Shell subsidiary company the NAM GLT project. The thrust-bearing disks, however, were not large enough to compensate for the high differential pressure across the compressor, and as a result of this, the maximum power could not be

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reached. The team decided to use spares kindly offered by NAM GLT to change the thrust-bearing disk for a larger one, which resulted in a 3-week delay. Despite good progress in the commissioning sphere, this delay was accommodated well before the operational date;

• Since not one of the compressors was operational before the offshore pipeline had to be pressurized with gas, there was no gas route available within the Anna Paulowna installation to supply warm gas towards the pig receiver as the starting point of the BBL pipeline towards the UK. Consequently a new, temporarily aboveground pipeline shortcut had to be installed with an extra heater in order not to jeopardize the pipeline commissioning critical path.

5. RESULTS The BBL pipeline system with associated installations and equipment was put into operation on 26 November 2006, while the commercial gas flow started on 1 December 2006 06:00 GMT and has been in operation ever since. Schedule overview Construction Commissioning Start Finish Start Finish

Planned 15-08-06 08-05-06 04-12-06 CSNH Actual 12-06-06 19-11-06 Planned 29-01-06 05-10-06 24-09-06 31-10-06 Pipeline Actual 29-01-06 28-10-06 19-09-06 15-11-06 Planned 01-12-06 1st gas in Actual 25-11-06

Starting-up The gas started to flow on 25th of November. At first the water dew point was quite high as can be seen in the adjacent figure 12. The water dew point decreased over time. The only problem at the time was that the water dew point was not quickly enough at the specified contract value. This meant that National Grid, as the responsible shipper, ordered to stop the gas flow at 18:15. The next day the gas flow started again and was approximately at 15:00 hours below the contracted value. The high water dew point was not caused by the pipeline, but was associated with the poor drying of the receiving installation at Bacton. As National Grid was able to mix the first gas with other gases we were fortunate enough to start up the BBL pipeline during the weekend of 25 and 26 November 2006. There was during start-up a close contact from the Central Command Post (CCP) in Groningen with operational staff from Shell in Bacton, project staff at the compressor station Anna Paulowna and of course operational staff at Warwick from National Grid. As can be seen from figure 12 we still like to point out that if we extrapolate the decreasing waterdewpoint value versus time, it can be concluded that we would already be under the contracted value at approximately 20:00 the same day we started with the first gas to flow from the Netherlands towards the UK. 6. EVALUATION Looking back, the authors would like to emphasize that the overall BBL project team was successful in having the gas flowing a few days before the planned commercial date. From the beginning it was considered quite a challenge to reach the project objective, but even 3 years after the handover date, it is still amazing to remember that all the project team members, contractors and colleagues were so successful. ‘Lessons learned’ sessions were held a few months after the handover. A few issues will be mentioned without further discussion:

• Project responsibilities should be well specified and separated;

Figure 12 : waterdewpoint versus time

• Commissioning and start-up teams should be well prepared and work together with engineering and construction teams and, as a result of that, start work at least 1½ years before the system is to be operational;

• The overall responsible commissioning manager should also be involved during the engineering process;

• It is desirable to have one engineerings manager responsible overall for all separate parts Although Gasunie, on behalf of the BBL Company VOF (as the operator of the BBL compressor station, onshore and offshore pipeline system), has encountered 2 major incidents with the emergency bearings of the electrically-driven motors of the compressor units, the overall availability and security of supply has been on average very high. The investigations of the ‘Root Cause Analyses’ are still in progress and, in the meantime, mitigating measures have been taken by the compressor unit supplier. After the completion of the project, Gasunie (as the operator) took over the responsibility for operating the pipeline and for maintaining the compressor station and the offshore pipeline. Shell Operations took over responsibility for maintaining the BBL facilities in Bacton. Taking over responsibility means that the operator should have sufficient knowledge and background information about the new system to be able to fulfil all obligations related to these responsibilities. The main lessons learned from the owner’s point of view are:

• The Project Team was acting on behalf of BBL Company VOF and built the pipeline system in accordance with the Functional and Project Specification and the jointly agreed Project Execution Plan. Due to the fact that BBL Company was not directly involved during the construction phase, the Project Team reported regularly to the BBL partners about costs, health, safety and environmental issues and progress of the project. During the construction phase, there was limited involvement by the new future operator of the pipeline. The first reason for this was the fact that a new compressor station was built. When there is a large modification project involving one of the existing Gasunie stations there is always much more involvement by the operator. The second reason was that new technologies were used. It was the first time that the Gasunie Project Team had to install large electromotor-driven compressors at a compressor station instead of gas turbines or gas-driven reciprocating motors. The last reason was the tight time schedule for completing the project. More involvement from “third parties” would endanger the completion time of the project;

• When the project was handed over to BBL Company as the owner and Gasunie as the operator of the pipeline system, the normal handover procedure was followed. A special handover document contained project information on the construction of the offshore pipeline with regard to relevant future operational aspects. No alignment meetings were organised between the BBL Project Team, Gasunie, as the operator and BBL Company, as the owner, to emphasize and to explain the background of the importance of these operational aspects;

• The offshore pipeline was hydrostatically tested at a normal hydrostatic test pressure. A MFL (Magnetic Flux Leakage) pig run to demonstrate the integrity of the pipeline was ordered by the Project team, however the BBL Company and its partners had to carry out this run, due to the fact that the system was already handed over. This type of MFL pig run gives a blueprint of the integrity of the pipeline. The project team and BBL Company VOF agreed to carry out an MFL pig run six months after it became operational. At that time, the project team was already disbanded and BBL Company took over the responsibility for the pig run. During the discussions of the results with the MFL contractor it was clear that the knowledge of the members of the project team responsible for the construction of the offshore pipeline would have been extremely valuable to explain all kind of anomalies;

• After closing out the BBL Construction phase, an inventory was made of all punch list items. During the first months of operation it became clear that the punchlist was much longer than agreed during the handover ceremony. Costs relating to the outstanding punchlist items were also much higher than forecast by the Project Team;

7. SUMMARY / CONCLUSIONS The project team was very successful in delivering the pipeline and associating installation in due time, while (as always) the construction period of time is enlarged, eating so to speak valuable time of the commissioning and start-up. However if the necessary commissioning and start-up activities are well structured, well prepared upfront and harmonised with all the different groups of people that are working on the project and within the responsible, operational departments. Moreover if the project risks are recognised and mitigated for it is indeed possible to be successful as has been well proven.

The period of time required to construct a pipeline system (3 years) is much less than the period of time of its whole operation (50 years). After three years of operating the pipeline system, BBL Company and Gasunie, as the operator of the pipeline, are of the opinion that the main lesson learned is that the new operator of the pipeline should be much more involved/integrated during the design and construction phase. 8. ACKNOWLEDGEMENT The authors like to acknowledge the good work of their colleagues of engineering-, operational-, asset management- and gas transportation departments in the first place. Only with good cooperation and good understanding it is possible to run a large project as the discussed ones. We are looking back to a very successful project and like to acknowledge the good work of all people and companies involded in this project. Especially we like to acknowledge the excellent work of the company Halliburton, which was contracted for the drying and pressurizing of the BBL on- and offshore pipeline. Moreover we like to thank employees of Statoil of their kindest reception and feedback on our offshore commissioning plan. All parties worked closely together in order to allow the project team to successfully deliver the BBL pipeline system on time. It has been a great challenge, a lot of work and long hours, but everyone has been working as one TEAM, meaning Together Everyone Achieves More.