Glossary
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Preload Reaction
Definition(s)
Preload Reaction
Maximum vertical reaction under a spudcan, VLo, supporting the in-water weight of the jack-up during the entire preloading operation. NOTE 1 The in-water weight is the full weight of the hull, variable load and preload ballast, plus the legs and spudcans and any contained water, reduced by the buoyancy in water of the legs and spudcans (calculated from their external dimensions). Soil buoyancy and the weight of any soil backfill above the spudcan are neglected. It is necessary to take care when accounting for water contained in the spudcan (in some cases this can be included in the quoted leg weight). NOTE 2 This is the maximum reaction on a spudcan, VLo, that would be obtained during preloading if the jack-up were installed on an infinitely rigid foundation. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsPreloading
Definition(s)
Preloading
Installation of the spudcans by vertical loading of the soil beneath a jack-up leg spudcan with the objective of ensuring sufficient foundation capacity under assessment situations through to the time when the maximum load is applied and held. NOTE Whilst three-legged jack-ups preload by taking water ballast on board, jack-ups with four or more legs typically achieve foundation preload by carrying the hull weight on pairs of legs in turn. This procedure is known as pre-driving and generally does not require the addition of water ballast. For the purposes of this part of ISO 19905, no distinction is made between preload and pre-drive. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsOperating Manual
Definition(s)
Operating Manual
Publication issued by the supplier/manufacturer, which contains detailed data and instructions related to the design, installation, operation, and maintenance of a particular tool.
Source:API SPECIFICATION 19TT, Specification for Downhole Well Test Tools and Related Equipment, First Edition, October 2016. Global StandardsOperating Manual
Publication issued by the manufacturer which contains detailed data and instructions related to the design, installation, operation and maintenance of equipment. Source: API SPEC 14A, Specification for Subsurface Safety Valve Equipment, Eleventh Edition, October 2005 (Reaffirmed June 2012). Global StandardsOperating Manual
Manual that defines the operational characteristics and capabilities of the jack-up in accordance with the IMO MODU code. NOTE The assessor is advised to ensure that the operations manual referenced is the latest revision and that any updated weight data are provided. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsMarine Operations Manual
Definition(s)
Marine Operations Manual
Manual that defines the operational characteristics and capabilities of the jack-up in accordance with the IMO MODU code. NOTE The assessor is advised to ensure that the operations manual referenced is the latest revision and that any updated weight data are provided. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsNominal Strength
Definition(s)
Nominal Strength
Strength calculated for a cross-sectional area, taking into account the stress raising effects of the macro-geometrical shape of the component of which the section forms a part, but disregarding the local stress raising effects from the section shape and any weldment or other fixing detail. NOTE Adapted from ISO 19902:2007, definition 3.34. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsMPME
Definition(s)
MPME
Value of the maximum of a variable with the highest probability of occurring over a defined period of time. NOTE 1 A defined period of time can be, for example, X hours. NOTE 2 The most probable maximum extreme is the value for which the probability density function of the maxima of the variable has its peak. It is also called the mode or modus of the statistical distribution. NOTE 3 Adapted from ISO 19901-1:2005, definition 3.19. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsMPME
Most probable maximum extreme. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsMost Probable Maximum Extreme
Definition(s)
Most Probable Maximum Extreme
Value of the maximum of a variable with the highest probability of occurring over a defined period of time. NOTE 1 A defined period of time can be, for example, X hours. NOTE 2 The most probable maximum extreme is the value for which the probability density function of the maxima of the variable has its peak. It is also called the mode or modus of the statistical distribution. NOTE 3 Adapted from ISO 19901-1:2005, definition 3.19. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsMean Zero-Upcrossing Period
Definition(s)
Mean Zero-Upcrossing Period
average period of the (up or down) zero-crossing waves in a sea state NOTE In practice the mean zero-crossing period is often estimated from the zeroth and second moments of the wave spectrum as.
Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global Standards
Mean Zero-Upcrossing Period
average intrinsic period of the zero-upcrossing waves in a sea state. NOTE 1 In practice, the mean zero-crossing period is often estimated from the zeroth and second moments of the wave spectrum as given by Equation (3.41-1):
where
f is the frequency in cycles per second (hertz);
m0 is the zeroth spectral moment and is equivalent to σ2, the variance of the corresponding time series;
m2 is the second spectral moment;
T2 and Tz are the average zero-crossing period of the water surface elevation, defined by the zeroth and second order spectral moments, (T2 = Tz);
ω is the wave frequency in radians per second.
NOTE 2 Adapted from ISO 19901-1:2005, definition 3.17.
Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global Standards
Mean Sea Level (MSL)
Definition(s)
Mean Sea Level
Arithmetic mean of all sea levels measured at hourly intervals over a long period, ideally 19 years. NOTE Seasonal changes in mean level can be expected in some regions and over many years the mean sea level can change. [ISO 19901-1:2005, definition 3.15]. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global Standards Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsMean Low Water Spring Tidal Level
Definition(s)
Mean Low Water Spring Tidal Level
Arithmetic mean of all low water spring tidal sea levels measured over a long period, ideally 19 years. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsMean High Water Spring Tidal Level
Definition(s)
Mean High Water Spring Tidal Level
Arithmetic mean of all high water spring tidal sea levels measured over a long period, ideally 19 years. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsMat-Supported Jack-Up
Definition(s)
Mat-Supported Jack-Up
Jack-up unit with the leg(s) rigidly connected by a foundation structure, such that the leg(s) are raised and lowered in unison. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsLowest Astronomical Tide
Definition(s)
Lowest Astronomical Tide
Level of low tide when all harmonic components causing the tides are in phase NOTE The harmonic components are in phase approximately once every 19 years, but these conditions are approached several times each year. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsLowest Astronomical Tide
Level of low tide when all harmonic components causing the tides are in phase. NOTE The harmonic components are in phase approximately once every 19 years, but these conditions are approached several times each year. [ISO 19901-1:2005, definition 3.12]s are approached several times each year. [ISO 19901-1:2005, definition 3.12]. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsLong-Term Operation
Definition(s)
Long-Term Operation
Operation of a jack-up on one particular site for more than the normal RCS special survey period of five years. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsLife-Safety Category
Definition(s)
Life-Safety Category
classification system for identifying the applicable level of life-safety for a platform. Source: ISO 19900:2013, Petroleum and natural gas industries – General requirements for offshore structures. Global StandardsLife-Safety Category
Classification system for identifying the applicable level of life-safety of personnel on a jack-up. NOTE 1 Categories for life-safety are the following (see 5.5.2): – S1: manned non-evacuated; – S2: manned evacuated; – S3: unmanned. NOTE 2 Adapted from ISO 19902:2007, definition 3.27. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsLeaning Instability
Definition(s)
Leaning Instability
Instability of an independent leg jack-up that can arise when the rate of increase of actions on the foundation with jack-up inclination exceeds the rate of increase of foundation capacity with depth. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsJoint Probability Metocean Data
Definition(s)
Joint Probability Metocean Data
Combinations of wind, wave and current that produce the action effect that can be expected to occur at a site, on average, once in the return period. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsJack-Up Owner
Definition(s)
Jack-Up Owner
Representative of the companies owning or chartering the jack-up. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsJack-Up
Definition(s)
Jack-Up
Mobile offshore unit with a buoyant hull and one or more legs that can be moved up and down relative to the hull. NOTE A jack-up reaches its operational mode by lowering the leg(s) to the seabed and then raising the hull to the required elevation. The majority of jack-ups have three or more legs, each of which can be moved independently and which are supported in the seabed by spudcans. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global Standards Source: ISO 19900:2013, Petroleum and natural gas industries – General requirements for offshore structures. Global StandardsIntrinsic Wave Frequency
Definition(s)
Intrinsic Wave Frequency
Wave frequency of a periodic wave in a reference frame that is stationary with respect to the wave. NOTE If there is no current, the reference frame is also stationary with respect to the sea floor. If there is a current, the reference frame moves with the same speed and in the same direction as the current. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsInfill
Definition(s)
Infill
Soil above the plan area of the spudcan arising from sediment transport or hole sidewall collapse. NOTE Infill is part of backfill (3.7). Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsInertial Loadset
Definition(s)
Inertial Loadset
Set of actions that approximates the effect of the inertial forces. NOTE An inertial loadset is used only in quasi-static analyses. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsIndependent Leg Jack-Up
Definition(s)
Independent Leg Jack-Up
Jack-up unit with legs that can be raised and lowered independently. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsFoundation Stability
Definition(s)
Foundation Stability
Ability of the foundation to provide sufficient support to remain stable when subjected to actions and incremental deformation. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsFoundation Fixity
Definition(s)
Foundation Fixity
Also called spudcan-soil rotational stiffness, is the rotational restraint offered by the soil supporting the foundation.
Source: ABS Guidance Notes on Geotechnical Performance of Spudcan Foundations, January 2017. Global StandardsFoundation Fixity
Rotational restraint offered by the soil to the spudcan. Source: ISO 19905-1:202, Petroleum and natural gas industries – Site-specific assessment of mobile offshore units – Part 1: Jack-ups. Global StandardsFootprint
Definition(s)
Footprint
After a jackup unit is removed from a site, depressions are left in the seabed where the spudcans were located. The soil in way of the footprints has modified physical profiles of the seabed and soil properties.
Source: ABS Guidance Notes on Geotechnical Performance of Spudcan Foundations, January 2017. Global Standards