35 Year Old Jackets Removed as a Single Piece

2011 ◽  
Author(s):  
Jochum C. G. van Hoof ◽  
Ruben de Bruin
Keyword(s):  
Dynamic Behavior ◽  
Wave Climate ◽  
Model Tests ◽  
Time Model ◽  
Project Duration ◽  
The North ◽  
Transport Distance ◽  
Single Piece ◽  
Heavy Lift ◽  
The North Sea

Heerema Marine Contractors (HMC) have removed and will be removing various platforms from the North Sea. For these projects Heerema has developed an unconventional method to remove and transport jackets: Jackets are lifted as one single piece and transported to the recycling yard whilst being suspended from both cranes of the Heavy Lift Vessel (HLV) Thialf. Two purpose built structures at the stern restrain the jackets from horizontal motions during transport. In summer 2010 three eight-legged jackets were removed and transported using this method (see Figure 1). The jackets weighed approximately 5,000 metric tonnes each and stood in 70–80m of water. The jacket removal resulted in load cases that were never considered during jacket design. Jacket strength appeared very marginal when cutting the jacket into several sections, but by lifting the jacket as one single section, all members remained connected and ensured a stable structure. Other benefits were reduction of the offshore project duration, the subsea cutting scope and the required vessel spread. Risk on weather downtime was reduced and safety improved by preventing back loading operations in an offshore environment. The transport distance with the jacket suspended from both Thialf cranes ranged from 200–300 nautical miles (1 1/2–2 1/2 days sailing). The final cuts and the jacket lifting required relatively low sea states. The wave climate for transport was determined with the assumption of a preceding weather sensitive operation, which is different to a transport that assumes a start at a random time. Model tests for these design sea states have been performed to accurately assess the Thialf dynamic behavior at its shallow transit draught. Additional analyses were performed to confirm the vessel-jacket dynamic interaction. During transport the so called ‘restraints’ gripped around the jacket corner legs, restraining the structure horizontally and preventing side loads on the cranes. During the three transports, motions have been measured and dynamic behavior corresponded well with the analyses. Removing and transporting these jackets as a single piece was a unique operation. The method worked well and resulted in a predictable, safe and time efficient jacket removal. This paper will address the removal method, including structural aspects, model tests and full scale verification.

Dynamic Behavior of a Novel Heave-Compensated Floating Platform for Well Interventions

2020 ◽  
Author(s):  
Marcelo A. Jaculli ◽  
Bernt J. Leira ◽  
Sigbjørn Sangesland ◽  
Celso K. Morooka ◽  
José Ricardo P. Mendes
Keyword(s):  
Dynamic Behavior ◽  
Small Diameter ◽  
Floating Platform ◽  
Floating Structure ◽  
Cross Sectional ◽  
Platform Design ◽  
The North ◽  
The North Sea ◽  
Heave Motion ◽  
Intervention Costs

Abstract A new type of floating platform design has been investigated. It consists of a relatively small semi-submersible floating structure with an air chamber that aims to keep a constant buoyancy, thus effectively reducing heave motion and enabling its use under harsh environmental conditions such as in the North Sea. It aims to provide an alternative solution compared to large floating structures, such as drillships and semi-submersible platforms, in terms of time availability, drilling costs and operational flexibility. One recent focus has been on the application of this platform for reducing well intervention costs. A small diameter (workover) riser may be used for installing the well control stack on the wet Christmas tree and for performing well intervention through the riser using a wireline cable. Alternatively, the operation can take place without a riser; this operation is termed riserless well intervention (RLWI). In this work, we investigate the dynamic behavior of this system, which is attached either to a wireline — for RLWI — or to a small-sized riser for well service through the riser. By modeling this system — which acts similarly to a passive heave compensation system — we have verified that this new platform indeed experiences smaller displacements when compared to conventional platform. The reduction observed varies depending on the platform design; in some cases, it reduces the displacement by a factor of two. A relatively heavier platform with a small cross sectional water plane area is found to be the best design option, but a lighter platform might be preferable for increased flexibility, as long as its dynamic behavior is satisfactory for safe operations.

Spectral wave climate of the North Sea

2007 ◽  
Vol 29 (3) ◽  
pp. 146-154 ◽  
Author(s):  
Alexander V. Boukhanovsky ◽  
Leonid J. Lopatoukhin ◽  
C. Guedes Soares
Keyword(s):  
North Sea ◽  
Wave Climate ◽  
The North ◽  
The North Sea

scholarly journals Decommissioning Plans for Fixed Offshore Platforms: A Brief Revision

2021 ◽  
Vol 9 (3) ◽  
Author(s):  
Marcio Soares Pinheiro ◽  
Paulo Roberto Duailibe Monteiro
Keyword(s):  
North Sea ◽  
Rio De Janeiro ◽  
The State ◽  
Oil Field ◽  
Offshore Platforms ◽  
The North ◽  
Campos Basin ◽  
Heavy Lift ◽  
Long Time ◽  
The North Sea

Brazil began to explore its seas in the 60’s of the XX Century looking for petroleum. This journey began in the Northeast and the first oil field produced offshore was the Guaricema Field, in the State of Sergipe. During the 70’s, Petrobrás found oil in the Campos Basin, between the States of Espírito Santo and Rio de Janeiro, that became the most important oil province in Brazil until the discovery of the Pre-Salt province, in the Santos Basin. As these fields are producing for a long time, many of them are already completely depleted or their production is in way of to be not commercial anymore, and their facilities need to be decommissioned. This review of decommissioning practices of fixed offshore platforms carried out worldwide has focus on the removal of topside with special vessels designed for this purpose or with conventional methods (crane vessels + barge). It will show the benefits of using specialised heavy lift vessels to remove the topsides and move it to shore for dismantling / recycling / reuse / disposal. The cases for study were the successful decommissioning projects in the North Sea: Brent B/D, Valhall QP, Viking, Curlew, Eider A, Golden Eye and Leman, Iwaki-Oki, Halfweg Q1, Yme and Ninian North.

Impact of Climate Change on the North Sea Offshore Energy Sector

2018 ◽  
Author(s):  
Nicolas Fournier ◽  
Galina Guentchev ◽  
Justin Krijnen ◽  
Andy Saulter ◽  
Caroline Acton ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
North Sea ◽  
Wave Climate ◽  
Energy Industry ◽  
Strong Impact ◽  
Impact Of Climate Change ◽  
The North ◽  
Climate Indicators ◽  
The North Sea

The complex nature of the energy industry across extraction, transportation, processing, delivery and decommissioning creates significant challenges to how the sector responds, adapts and mitigates against risks posed by the changing future climate. Any disruption in this interconnected system will affect both industry and society. For example, in the summer of 2005 Hurricane Katrina and a month later Hurricane Rita had wide reaching impacts on the US offshore Oil and Gas industry which resulted in an increase in global oil prices due to loss of production and refinery shutdowns in the Gulf of Mexico. Preparing, mitigating and adapting to these climate changes is dependent upon identifying appropriate climate indicators as well as the associated critical operational thresholds and design criteria of the identified vulnerable assets. The characterization and understanding of the likely changes in these climate indicators will form the basis for adaptation plans and mitigating actions. The Met Office in collaboration with energy industry partners, under the Copernicus Clim4energy European project, has developed a Climate Change Risk Assessment tool, which allows the visualization and extraction of the most recent sea level and wave climate information to evaluate their future changes. This study illustrates the application of this tool for evaluation of the potential vulnerability of an offshore infrastructure in the North Sea. The analysis shows that for this asset there is a small increase in sea level of 0.20–0.30 m at the location of interest by 2050. However, there is a small decrease or no consistent changes projected in the future wave climate. This wave signal is small compared to the uncertainty of the wave projections and the associated inter-annual variability. Therefore, for the 2050s time horizon, at the location of interest, there is no strong impact of climate change at the annual scale on the significant wave height, the sea level and thus the associated climate change driven extreme water level. However, further analysis are required at the seasonal and monthly scales.

1300 Tons Grouted Integrity Support Installation Case Study

2020 ◽  
Author(s):  
Beatriz Alonso Castro ◽  
Roland Daly ◽  
Francisco Javier Becerro ◽  
Petter Vabø
Keyword(s):  
North Sea ◽  
Structural Integrity ◽  
High Strength ◽  
Regulatory Compliance ◽  
Lessons Learned ◽  
Oil Field ◽  
The North ◽  
Future Production ◽  
Heavy Lift ◽  
The North Sea

Abstract The North sea Yme oil field was discovered in 1987, production started in 1996 and ceased after 6 years when it was considered no longer profitable to operate. In 2007 a new development was approved, being Yme the first field re-opened in the Norwegian Continental Shelf. The concept selected was a MOPUStor: comprising a jack-up unit grouted to a subsea storage tank. Due to compromised structural integrity and lack of regulatory compliance that came to light shortly after installation, the platform was required to be removed [1]. The remaining riser caisson and the future 1050 t wellhead module required a support to allow the re-use of the facilities and tap the remaining oil reserves. The innovative tubular frame support was designed as a braced unit, secured to the existing MOPUstor leg receptacles and holding a grouted clamp larger than typical offshore clamps for which design guidance in ISO is available. The existing facilities had to be modified to receive the new structure and to guide it in place within the small clearances available. The aim of this paper is to describe the solutions developed to prepare and verify the substructure for installation; to predict the dynamic behavior of a subsea heavy lift operation with small clearances around existing assets (down to 150 mm); and to place large volume high strength grouted connections, exceeding the height and thickness values from any project ever done before. In order to avoid early age degradation of the grout, a 1 mm maximum relative movement requirement was the operation design philosophy. A reliable system to stabilize the caisson, which displacements were up to 150 mm, was developed to meet the criteria during grouting and curing. In the stabilizer system design, as well as the plan for contingencies with divers to restart grouting in the event of a breakdown, the lessons learned from latest wind turbine industry practices and from the first attempt to re-develop the field using grouted connections were incorporated. Currently the substructure is secured to provide the long term integrity of the structure the next 20 years of future production in the North Sea environment.

scholarly journals WAVE CLIMATE ANALYSIS FOR ENGINEERING PURPOSE

1976 ◽  
Vol 1 (15) ◽  
pp. 2 ◽  
Author(s):  
Hans H. Dette ◽  
Alfred Fuhrboter
Keyword(s):  
Wave Climate ◽  
Incoming Wave ◽  
Offshore Area ◽  
The North ◽  
Wave Measurements ◽  
Wind Velocities ◽  
Wave Heights ◽  
The North Sea ◽  
One Year ◽  
Climate Analysis

The North Sea (Fig. 1) is known as a random sea with depths in the southern part between 40 m and 100 m so that in contrary to the Atlantic and Pacific coastlines deep sea wave conditions do not exist. After four years of comprehensive wave measurements in the offshore area of the Island of Sylt near the Danish border a general analysis of the wave climate in that region was possible. In this paper results and suggestions will be presented under the aspect of replacing qualitative judgements by quantitative statements which are derived from the knowledge of the adjacent wave climate. Because the wave action varies from year to year a general time unit is not advisable for the evaluation of shore processes; therefore the time scale should be substituted by the integral of incoming wave energy occurring after a certain time. The investigated method of expressing the total energy of one season or one year in the electrical unit Kilowatthour (kWh) per meter (m) width of shoreline could prove in future as a feasible way of classifying the irregular seasonal and yearly wave intensities. It is further shown that wave measurements over a period of several years can be sufficient for the investigation of correlations between the wind velocities occurring from all directions and the resulting wave heights. In case of satisfying correlation factors it will then be possible to carry out feedback operations for periods from which only records of wind velocities and directions are available and even to hindcast the wave heights for certain not yet measured wind velocities.

The Gjøa Semi: a North Sea project relevant for Western Australia

2011 ◽  
Vol 51 (1) ◽  
pp. 589
Author(s):  
Kristian Aas ◽  
Lars Bjørheim
Keyword(s):  
North Sea ◽  
Western Australia ◽  
Oil And Gas ◽  
Development Project ◽  
Conceptual Level ◽  
Field Development ◽  
The North ◽  
Heavy Lift ◽  
The North Sea ◽  
Field Location

Gjøa was the largest field development project in Norway in 2010. Gjøa was proven in 1989 and are now being developed together with nearby Vega satellites. The combined reserves are estiThe recent Gjøa field development in the North Sea has many features that are relevant for the oil and gas developments north of Western Australia. While the field location is not very similar to the north of Western Australia, the field development solution is very relevant. Several subsea clusters are tied back to a semi-submersible platform with export of gas and condensate via pipelines to shore. Other aspects to the project that are relevant to Western Australia are split location engineering between Norway and India, fabrication of the hull in Korea and subsequent heavy lift transport to the assembly yard, pre-installation of the mooring system, and tow to field with ocean going tug boats. The semi concept, which was used for the Gjøa development, is a mature technology with few technical challenges on a conceptual level. On the other hand the building of an oil and gas platform for A$2 billion has many challenges, both economical and technical, that have to be solved to have a successful project for both the client and the contractor.

scholarly journals Wave Climate Change in the North Sea and Baltic Sea

2019 ◽  
Vol 7 (6) ◽  
pp. 166 ◽  
Author(s):  
Antonio Bonaduce ◽  
Joanna Staneva ◽  
Arno Behrens ◽  
Jean-Raymond Bidlot ◽  
Renate Anna Irma Wilcke
Keyword(s):  
Climate Change ◽  
Baltic Sea ◽  
Wave Height ◽  
North Sea ◽  
Significant Wave Height ◽  
Wave Climate ◽  
Significant Wave ◽  
The North ◽  
The North Sea

Wave climate change by the end of the 21st century (2075–2100) was investigated using a regional wave climate projection under the RCP 8.5 scenario. The performance of the historical run (1980–2005) in representing the present wave climate was assessed when compared with in situ (e.g., GTS) and remote sensing (i.e., Jason-1) observations and wave hindcasts (e.g., ERA5-hindcast). Compared with significant wave height observations in different subdomains, errors on the order of 20–30% were observed. A Principal Component (PC) analysis showed that the temporal leading modes obtained from in situ data were well correlated (0.9) with those from the historical run. Despite systematic differences (10%), the general features of the present wave climate were captured by the historical run. In the future climate projection, with respect to the historical run, similar wave climate change patterns were observed when considering both the mean and severe wave conditions, which were generally larger during summer. The range of variation in the projected extremes (±10%) was consistent with those observed in previous studies both at the global and regional spatial scales. The most interesting feature was the projected increase in extreme wind speed, surface Stokes drift speed and significant wave height in the Northeast Atlantic. On the other hand, a decrease was observed in the North Sea and the southern part of the Baltic Sea basin, while increased extreme values occurred in the Gulf of Bothnia during winter.

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