Site-specific assessment (SSA) 

A Site-Specific Assessment (SSA) is performed for a jack-up before it can go on location. It presents the suitability of a particular jack-up to perform planned operations at a specific site. Our jack-up SSAs are performed strictly in accordance with the ISO-19905-1:2016 standard for performing SSA. In addition to support such as preloading guidance, checks are performed on the following key items: 

  • The structural strength of the leg, jacking system and leg-to-hull interface
  • Overturning stability 
  • Foundation capacity

At Calypso, we have successfully standardized performing site-specific assessments (SSAs) for jack-ups. We can confidently offer SSAs at a fixed low price and at a fixed delivery time of only three days.

Our SSAs are created to be of the highest quality, focusing on the following aspects: 

  • Clarity for direct implementation in procedures
  • Optimized use of the jack-up with maximized workability
  • Flexibility to allow for operational changes
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Example SSA

Services brochure

Sample LPA

Leg Penetration Analysis (LPA) 

A Leg Penetration Analysis (LPA) is performed for a jack-up before it can go on location, either as part of an SSA or as a stand-alone analysis. It determines the minimum and maximum expected penetrations of the jack-up legs. It provides preloading guidance and identifies geotechnical hazards, such as scouring, footprints and leg-extraction issues.

Our jack-up LPAs are performed in accordance with the ISO 19905-1:2016 standard for jack-up assessment. We offer LPAs within two days at a fixed low price.

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 Going-on-location analysis

A Going-on-Location (GOL) analysis – part of a Site-Specific Assessment for Installation (SSA-I) – is performed to determine allowable wave conditions for installation of a jack-up at a specific or generalized site. The GOL report details the allowable conditions and is directly usable on-board in combination with the environmental forecast.

A hydrodynamic and structural model of the jack-up is used in combination with a state-of-the-art soil interaction model to simulate the operation. Any type of soil can be modeled, including the most challenging rocky seabed.

Orcaflex model of a jack-up
This image shows a penetration resistance curve for a punch trough event

Punch-through tolerance assessment 

The results of an SSA may indicate a risk of punch-through occurring. The consequences of an unmitigated punch-through event and risk of progressive failure for a jack-up at a specific site may be analyzed to assess the risk in detail.

The punch-through tolerance report addresses the expected maximum settlement, tilt and resulting freeboard and leg moments. Strength checks are performed to assess the consequences for the structure.

Gap-bridging monitoring 

A monitoring campaign should bridge the gap between the on-board engineering reality and the desktop engineering reality. 
If large uncertainties are present in a desktop engineering model, these may lead to (overly) conservative assessments. Gap-bridging monitoring may be used to reduce uncertainties and thereby increase the workability and to expand the operational season of a jack-up.
The most lean monitoring campaign consists of applying a motion sensor on-board combined with detailed environmental forecast/hindcast. More detailed campaigns may include measurement of strains, position, waves, wind and current.
This image shows a Barstool type structural model (Orcaflex) of a jack-up, extreme value distribution and spectrum, used in the monitoring software suite for gap-bridging monitoring

Jack-up conversion support 

Jack-ups may be converted to support other operations than originally intended. Calypso supports enhancements, such as crane boom extension, and full conversion, such as from mobile drilling to fixed production unit. The jack-up may have to be re-classified and structural analysis of (part of) the hull may be required. 

Detailed geotechnical analysis and risk assessment 

A geotechnical risk assessment is an in-depth analysis of geotechnical risks associated with going-on-location, preloading, elevated operation, storm survival and going-off location of a jack-up at a specific site. The aim of the geotechnical risks assessment is to classify risks, quantify mitigative measures, support ALARP risk operations and to be included in HAZOP studies. 

Geotechnical causes of risks include presence of boulders and unexploded objects (UXO), irregular bathymetry and footprints, loose or weak top soil, rocky seabed, seismic activity (earthquake), insufficient geotechnical data and complex or irregular soil layering. Geotechnical risks include scouring, liquefaction, settlement, punch-through, sliding and leg-splay leading to leg moments and rack-phase difference (RPD).


Tender support 

A technically well-founded tender proposal helps securing projects and ensures that expectations are managed and aligned. We support jack-up owners in writing tender proposals and we deliver technical content, including uptime percentage estimates and weather limitations for planned operations. 

We support developers of oil&gas fields, wind farms and civil projects in writing tender documents including RFQs and reviewing received tender proposals. We perform third-party checks on received technical documents including SSAs and LPAs. 


Hydrostatic stability and hydrodynamic motion analysis 

The motion behavior and stability of jack-ups is different from other vessels and requires a jack-up engineering hydrodynamicist for optimal assessment. We offer free floating stability studies, ballast plans and hydrodynamic motion analyses. 

Jack-ups have motion limits due to the strength capacity at the connection between the hull and the leg. These limits are to be assessed for any dry tow and in special cases also for wet tow or field moves. The motion limits are translated to sea state limits and may be applied to objectively define workability.