Recent papers from UWA/COFS have presented cutting edge developments in subsea foundation design which can allow significant optimisation of foundation sizes. This has direct practical benefits that have been seen in practise. As such, these papers have been of great use to the offshore industry and they are well summarised in this paper. Starting from the codified approaches of developing VHM interaction envelopes, how these have been improved upon to generate refined VHMT envelopes, how further gains can be made by accounting for consolidation from sustained vertical and lateral loading and then moving onto their work on sliding foundations. A similar publication was also made at OTC (OTC-27703)
One of the critical aspects in subsea shallow foundation is the ability to assess them differently to fixed offshore installations which is typically the focal point of design codes). The figures below demonstrate the difference in typical loading regime and how this may impact the respective soil strength over time from foundation design perspective.
In the final section of the paper a worked example of presented showing that for a particular PLET it may be possible to reduce the foundation size by 75% using the design methods provided, in the end moving from a fixed foundation with a structural sliding mechanism to accommodate pipeline expansion to a foundation which is designed to slide upon the seabed.
The following observations are made:
As such, the paper summarises some excellent research which allows industry to optimise the way that shallow foundations can be designed. However, the worked example that is provided does not best reflect how it can be used to optimise PLET foundation design.
The downturn of the global oil and gas market has challenged every professional within the industry to look at the way they work and look to where costs can be reduced or removed.
Design engineers could be forgiven for thinking that their calling would be optimise their analyses as far as possible therefore saving steel and fabrication costs with the knock on effect of improving installability / offshore construction costs.
Is this the future?
The few oil & gas projects, however, which have been sanctioned over the past few years have been driven forward at a relentless pace putting what would have previously been seen as ‘fast track’ to shame. The obvious way to accommodate this change has been to squeeze the engineering schedule whilst accelerating fabrication. The results is commencement of fabrication (and upon occasion, completion of fabrication) before the design has been completed. Rather than optimise, engineers are forced to design with margin attempting to allow for uncertain input data and potential for unforeseen (but inevitable) changes. Within this framework there is limited opportunity for optimisation.
Stand-alone/single company FEED studies and interfacing with 3rd parties are two of the main obstacles to this type of engineering/scheduling. To this end we have seen a number of mergers or alliances of large companies with historically different specialisms (technipfmc, Subsea7 and OSS, KG7). These link-ups should facilitate the flow of critical design data which in theory, should assist earlier commencement of detailed design. How this fits in with the traditional project delivery approach remains to be fully realised. However the way that offshore oil & gas projects are delivered has changed and will continue to change significantly over the coming years.
Over the past few years however, it has been common for operators to engage site investigation contractors at an extremely early PRE-FEED phase on complex developments. It would not be uncommon for years of investigation and geohazard assessment to ensue in an effort to understand the project ground risk prior to final investment decisions.
With the changes we have seen to the how end users of the geotechnical, geophysical and geohazard data will execute projects. Will or how will the role of SI contractors be impacted by the changing nature of the offshore oil & gas industry? Can this be accommodated as the industry moves into ever more challenging field development?
The Society for Underwater Technology (SUT) held the 8th Offshore Site Investigation & Geotechnics (OSIG) conference in September at the Royal Geographical Society (RGS) in London.
The OSIG is held every 5 years and is dedicated to offshore geotechnical engineering, site investigations, geohazards and geosciences. It stands alongside the ISFOG (International Symposium on Frontiers in Offshore Geotechnics) as a highlight in the conference calendar.
This edition of the conference title was entitled “Smarter Solutions for Future Offshore Developments” with the following challenge in the call for papers:
“The challenges currently faced by the offshore oil & gas industry call for innovative approaches to improve efficiency and rigour in practice, while the offshore renewable energy industry has identified and addressed, through major research programmes, key technical issues that must be solved to support its growing strength. High profile international incidents have also occurred across all sectors in recent years that pose significant data acquisition, engineering and operational challenges.”
With this in mind it is interesting to note that this is first time that delegates from the renewables sector outnumbered those from oil & gas at the OSIG conference.
In addition to the 4th McClelland Lecture being delivered at the conference the following keynote papers were presented:
The published proceedings (comprising 1323 pages) are split into 2 volumes and 12 sections including:
Parallel presentation sessions were introduced in order to fit in a huge number of presentations and presentations times were kept short (5 min in the parallel sessions, which was described as a speed dating equivalent for geotechnical engineers).
A knovel approach to Q&A was available in plenary sessions where delegates could use a social media forum to submit questions during the presentations. This has benefits and draw backs (with some delegates choosing to make anonymous questions or using fake names which takes away from the collaborative spirit of the event). However, it probably encouraged more questions which is a positive if not making more work for session chairs.
A few of the conference papers (in addition to the keynotes above) which best answer the challenge made in the call for papers, in my opinion are summarised below:
Over the course of the 3 days there were some excellent presentations and there are of course many other fantastic papers. A great event and we look forward to the next one in 5 years time.