LOTOS Petrobaltic has commenced another stage of a project to construct a 75-kilometre long gas pipeline between the B8 field production hub and the Energobaltic CHP plant in Władysławowo. The pipeline, laid on the Baltic seabed, is now being secured with concrete mattresses. The task is being performed by Sylur, a multi-purpose vessel.

According to the project plan, the laid pipeline is to be protected with dedicated concrete mattresses positioned at 50m intervals. Their main task is to stabilise the pipeline on the seafloor as well as safeguard it against displacement due to trawling activity.

The operation is the responsibility of the B8 Project Subsea Team. “We are at the halfway point,with 250 mattresses already put in place,” says Artur Wójcikowski, head of the Subsea Team at LOTOS Petrobaltic. “The work is going smoothly, though its pace of course depends on the weather conditions and the sea depth.”To do its job, Sylur has to first position itself above the subsea pipeline with a high degree of precision. Once the vessel finds the right location, its deck-mounted crane picks up a mattress and lowers it underwater.

The pipeline runs at various depths – from a few to as many as 87 metres (the closer to the hub, the deeper the sea), which is why the team has been relying on Sylur’s subsea navigation system to precisely lay mattresses in preselected spots over the pipeline. Released from the dedicated lifting yoke, a mattress is left on the seabed. The yoke features a subsea CCTV system, which allows direct control over the laying of mattresses on the pipeline. Once a mattress has been properly laid, the vessel sails to the next spot where another mattress is to be lowered onto the bottom.
 

 At the next stage of the project, the pipeline will be tested for leaks and commissioned. The entire system will then be connected to a production hub on the B8 field, which is currently being upgraded and will eventually replace the LOTOS PETROBALTIC rig operating there.

“The pipeline construction project commenced in 2016 with horizontal directional drilling (HDD) of a 1.5-kilometre bore hole.It is the second longest HDD hole in Poland and the longest one which ends offshore,” says Grzegorz Strzelczyk, President of the Management Board of LOTOS Petrobaltic. “Currently we are in the process of securing the offshore section of the pipeline between the B8 field and the Władysławowo CHP plant.Associated gas extracted during oil production from the field will be mainly used for energy generation for Władysławowo. It is noteworthy that our first gas pipeline, which runs between the Baltic Beta rig on the B3 field and the Energobaltic CHP plant, has been transmitting gas since July 2003,” adds Strzelczyk.

Natural gas will be transmitted at an operating pressure of up to 130 bar in a steel pipeline with an outer diameter of 11.5 cm.

Pipeline on the seabed

The gas pipeline was laid in 2017 by winding it off a reel mounted on board of Sylur and feeding it to a dedicated tensioner to ensure adequate tension of the pipeline during the operation. A special jib was installed on the stern of the ship to ensure proper curvature of the pipeline and thus its gradual and safe layout on the seabed. Aboard Sylur, working on the pipelay project, were also a team of experts from CORTEZ Subsea, a UK-based company, supported by LOTOS Serwis specialists. Kambr, an assisting tugboat, was also involved in the operation. Her task was to lay weights during the lifting and discharging of subsequent sections of the pipeline to prevent movement of the loose end of the already laid pipeline. The tugboat also assisted in inspecting the pipeline layout.

Surgical precision

In 2016, the end of the pipeline which is to transmit gas from the B8 field to the Energobaltic CHP plant was entered into a borehole drilled in the Baltic seabed. With the borehole being nearly 1.5 km long, the fact that the drill bit resurfaced only 20 cm from the designed receiving hole can be considered a fine example of almost surgical precision.

Once the borehole was ready, the pipeline was passed through it. To complete the operation, an approximately 15m section of the laid pipeline was secured on the site of the Energobaltic CHP plant.

Energy for Władysławowo

Natural gas (separated from crude oil produced from the B8 field) will be transported ashore through the pipeline for treatment at the expanded facilities situated on the site of the Energobaltic CHP Plant in Władysławowo, where it will be used for energy generation for the town.

The principal business activities of Energobaltic, a direct subsidiary of LOTOS Petrobaltic, comprise production and sale of LPG (a mixture of propane and butane), natural gas condensate, as well as heat and electricity. The Władysławowo CHP plant separates propane/butane and condensate from the raw material supplied by the pipeline. Gas associated with crude oil deposits is typically a mixture consisting of methane (45%), heavy hydrocarbons (20%), and propane/butane.

Heat generated by the CHP plant is sold locally to both retail and institutional customers, while its electricity output is sold to an electricity distribution company. Gas products, i.e. LPG and condensate, are sold under supply contracts with Grupa LOTOS S.A.

Gas supplies from the B3 field in the Baltic Sea have allowed the Władysławowo CHP plant to reduce annual coal consumption by approximately 75,000 tonnes, including:

• annual coal consumption for electricity production – by 36,000 tonnes
• annual coal consumption for heat production – by 7,000 tonnes
• annual coal consumption for propane/butane production – by 32,000 tonnes.

Chart presenting energy production from offshore Baltic gas

B8 field:

• discovered in 1983 in the Polish Exclusive Economic Zone of the Baltic Sea;
• located at a longitude close to that of the town of Hel, nearly 68 km north of the coastline and 2.1 km under the seabed. It is situated approximately 33 km west of the B3 oilfield (the first oilfield discovered in the Polish zone of the Baltic Sea, 70 km north of Rozewie), from which LOTOS Petrobaltic currently produces crude oil (several thousand barrels per day) and natural gas;
• covered by a hydrocarbon production licence granted in 2006 until 2031;
• its recoverable reserves, proven by an independent consultant, are estimated at 27m barrels of oil and 484 mcm of gas.

External Communications Department, Grupa LOTOS S.A., ul. Elbląska 135, 80-718 Gdańsk, Poland, tel. (+48) 58 308 83 88, (+48) 58 308 72 29, e-mail: media@grupalotos.pl