OIL & GAS INDUSTRY FOCUS
be programmed and integrated into the superordinate control of the brine plant. The mounting plate, complete with all automation components, was substituted and connected on-site. Once the plant had been modified and reconnected, various tests were carried out. Following cold commissioning, the safety technology had to be approved by specialists. Only then could the removal of the brine and the filling with natural gas begin. The automation experts were also given the task of training the operators.
SAFETY: THE OVERRIDING CRITERION After leaching the cavern is full of salt water (brine). Now the water has to be removed under pressure. This is done by introducing natural gas at higher pressure into the cavern which acts as a “cushion” pressing down on the column of brine. The brine removal pipe extends almost down to the lower end of the cavern. Thus the growing cushion of gas forces the brine out through the brine removal string. The brine displaced from the cavern first passes through the degassing tank, where small amounts of natural gas disperse. It is then pumped into the settling tank of the brine plant, where mud, sludge and larger particles can sediment out. These are disposed of separately. As during the leaching process, the remaining salt water is channeled through a pipeline approximately 45 km long and flows into the North Sea near Rysum. During brine removal and the first
filling with gas there are two potentially critical scenarios, either of which could lead to a gas escape. In the first scenario, the casing of the brine removal string is damaged by a subterranean rockslide when rocks in the salt dome break off and fall. In the second scenario, the cavern is filled with gas to below the level of the brine removal string. Both scenarios would have serious consequences. Kerner explained: “In a gas breakthrough, natural gas enters the
Figure 3b: A different view of the modified plant (Copyright: Rösberg)
COMPANY BOX 1: ASTORA GMBH & CO. KG
Astora plans, builds and operates natural gas storage facilities according to the highest ecological and safety standards. And not just because they are a requirement. Responsibility for people and the environment is expressed in the use of efficient technologies and reliable infrastructure, and is shown every day in the care taken by its employees. Health, environmental protection and safety are basic to
the reliable operation of plants and are clear priorities, on a par with economic efficiency. This principle determines the actions and decisions of the enterprise and is the foundation for its long-term success.
Figure. 4: Frank Soschinka, operations manager of astora (Copyright: astora)
brine removal string at high pressure. This would greatly accelerate the brine already in the pipe, which would exert great pressure on the wellhead. Thus it is essential to avoid a scenario of this kind with the help of functional safety systems and instrumentation and control engineering.” For this reason, the pressure at the wellhead is continuously and multiply monitored. If irregularities occur, a control valve closes the pipe completely within a few seconds. This prevents any pressure surges. Once the control valve is closed, all other safety- related on/off valves can be closed.
COMPANY BOX 2: RÖSBERG ENGINEERING GMBH
Rösberg Engineering GmbH, founded in Karlsruhe in 1962, offers tailored automation solutions created by around 100 employees working at five locations in Germany and China, for internationally active enterprises in the process industry. Today RÖSBERG is an internationally successful automation engineering company and developer of
software solutions. Its scope includes basic and detail engineering for the automation of process and production plants as well as the configuration, delivery and commissioning of distributed control systems. The enterprise also has extensive project planning and user experience in the implementation of safety- related controls, is an expert in functional safety, and offers sector-specific software solutions in the area of information technology. The I&C-CAE system ProDOK NG has enjoyed international success for more than 30 years now. Together under the name of Plant Solutions ProDOK NG, the digital plant documentation system LiveDOK NG – with the app
LiveDOK.mobile – and the Plant Assist Manager (PAM) support plants throughout their operation, from planning, construction and commissioning through to modernisation, expansion and decommissioning.
EIGHT REMAINING CAVERNS FILLED When the brine removal plants had been modernised and adapted, the automation experts were also awarded the contract for the brine removal process. For this purpose the software of each plant was adapted to the relevant cavern, and the start-up of brine removal was supported by the automation experts. Although the size of a cavern is known, when filling it with gas for the first time the sensitive judgement of experienced operators is needed to decide when the maximum filling quantity has been reached. One useful factor in determining this is that the brine removed from the cavern is continuously monitored at the degassing tank for its gas content. The gas content in the brine gives an indication of how closely the gas filled into the cavern is approaching the lower end of the brine removal string. In most cases, two caverns in parallel operation were tendered as one project; the assignments, totaling four in all, were carried out gradually by the company from Karlsruhe. In the meantime the first gas filling has now been completed for all eight remaining caverns. Frank Soschinka (Figure. 4) operations manager of astora GmbH & Co. KG at the Jemgum storage facility, regrets that the ten years’ cooperation is coming to an end: “Over the years the Rösberg team has not only proved very reliable and has always kept dependably to what was agreed – they have also been very pleasant to work with at a personal level.”
Rösberg Engineering
www.roesberg.com
www.LiveDOK.com
PROCESS & CONTROL | APRIL 2020 25
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36
