oSIST prEN ISO 19901-1:2024

SLOVENSKI STANDARD
01-oktober-2024
Naftna in plinska industrija, vključno z nizkoogljično energijo - Posebne zahteve za
naftne ploščadi - 1. del: Določila za načrtovanje in obratovanje ob upoštevanju
oceanografskih in meteoroloških vidikov (ISO/DIS 19901-1:2024)
Oil and gas industries including lower carbon energy - Specific requirements for offshore
structures - Part 1: Metocean design and operating considerations (ISO/DIS 19901-
1:2024)
Erdöl- und Erdgasindustrie - Spezielle Anforderungen für Offshore-Anlagen - Teil 1:
Grundsätze für die Auslegung und den Betrieb auf dem offenen Meer (ISO/DIS 19901-
1:2024)
Industries du pétrole et du gaz naturel - Exigences spécifiques relatives aux structures
en mer - Partie 1: Dispositions océano-météorologiques pour la conception et
l'exploitation (ISO/DIS 19901-1:2024)
Ta slovenski standard je istoveten z: prEN ISO 19901-1
ICS:
75.180.10 Oprema za raziskovanje, Exploratory, drilling and
vrtanje in odkopavanje extraction equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 19901-1
ISO/TC 67/SC 7
Oil and gas industries including
Secretariat: BSI
lower carbon energy — Specific
Voting begins on:
requirements for offshore
2024-08-15
structures —
Voting terminates on:
2024-11-07
Part 1:
Metocean design and operating
considerations
ICS: 75.180.10
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Reference number
ISO/DIS 19901-1:2024(en)
DRAFT
ISO/DIS 19901-1:2024(en)
International
Standard
ISO/DIS 19901-1
ISO/TC 67/SC 7
Oil and gas industries including
Secretariat: BSI
lower carbon energy — Specific
Voting begins on:
requirements for offshore
structures —
Voting terminates on:
Part 1:
Metocean design and operating
considerations
ICS: 75.180.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2024
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
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Published in Switzerland Reference number
ISO/DIS 19901-1:2024(en)
ii
ISO/DIS 19901-1:2024(en)
Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms.10
4.1 Symbols .10
4.2 Abbreviated terms . 12
5 Determining the relevant metocean parameters .12
5.1 General . 12
5.2 Expert development of metocean criteria. 13
5.3 Selecting appropriate parameters for determining design actions and action effects . 13
5.4 The metocean database . 15
5.5 Storm types in a region . 15
5.6 Directionality . 15
5.7 Extrapolation to extreme and abnormal conditions . 15
5.8 Metocean parameters for fatigue assessments .16
5.9 Metocean parameters for short-term activities.17
5.10 Metocean parameters for medium-term activities .18
6 Water depth, tides and storm surges .18
6.1 General .18
6.2 Tides .19
6.3 Storm surges .19
6.4 Extreme water level .19
7 Wind .20
7.1 General . 20
7.2 Wind actions and action effects .21
7.3 Wind profile and time-averaged wind speed . 22
7.4 Wind spectra . 22
8 Waves .22
8.1 General . 22
8.2 Wave actions and action effects . 23
8.3 Sea-states — Spectral waves .24
8.3.1 Wave spectrum .24
8.3.2 Directional spreading .24
8.3.3 Wave periods .24
8.3.4 Wave kinematics — Velocities and accelerations .24
8.4 Regular (periodic) waves . 25
8.4.1 General . 25
8.4.2 Wave period . 25
8.4.3 Wave kinematics — Velocities and accelerations . 25
8.4.4 Intrinsic, apparent and encounter wave periods . 26
8.5 Maximum height of an individual wave for long return periods .27
8.6 Linear and non linear wave models .27
8.7 Wave crest elevation .27
9 Currents.28
9.1 General . 28
9.2 Current velocities . 28
9.3 Current profile . 29
9.4 Current profile stretching . 29
9.5 Current blockage . . 29

iii
ISO/DIS 19901-1:2024(en)
9.6 Tidal Currents . 29
10 Other environmental factors .30
10.1 Marine growth . 30
10.2 Tsunamis . 30
10.3 Seiches . 30
10.4 Sea ice and icebergs . .31
10.5 Snow and ice accretion .31
10.6 Thunderstorms and Lightning .31
10.7 Rainfall .31
10.8 Squalls and Downbursts .31
10.9 Internal Waves and Solitons .32
10.10 Shelf Waves and Eddies.32
10.11 Infragravity Waves .32
10.12 Seawater Temperature . 33
10.13 Miscellaneous . 33
11 Collection of metocean data .33
11.1 General . 33
11.2 Common requirements . 34
11.2.1 General . 34
11.2.2 Instrumentation. 34
11.3 Meteorology . 34
11.3.1 General . 34
11.3.2 Weather observation and reporting for helicopter operations . 34
11.3.3 Weather observation and reporting for weather forecasting services . 35
11.3.4 Weather observation and reporting for climatological purposes . 35
11.4 Oceanography . 35
11.4.1 General . 35
11.4.2 Measurements and observations. 36
11.5 Data quality control . 36
12 Verification of Weather Forecast Information .36
12.1 General . 36
13 Information concerning the annexes .36
13.1 Information concerning Annex A . 36
13.2 Information concerning the Regional Annexes .37
Annex A (informative) Additional information and guidance .38
Annex B (informative) Northwest Europe .107
Annex C (informative) West Coast of Africa .117
Annex D (informative) Offshore Canada . 128
Annex E (informative) Sakhalin/Sea of Okhotsk. 158
Annex F (informative) Caspian Sea .183
Annex G (informative) South East Asian Sea .201
Annex H (informative) Mediterranean Sea .224
Annex I (informative) Brazil . 246
Annex J (informative) US Gulf of Mexico .262
Annex K (informative) US Coast of California .312
Annex L (informative) Other US Waters .317
Bibliography .321

iv
ISO/DIS 19901-1:2024(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO's adherence to the WTO principles in the Technical Barriers to Trade (TBT)
see the following URL: Foreword - Supplementary information
This document was prepared by Technical Committee ISO/TC 67] Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries, Subcommittee SC 7, Offshore structures
This third edition cancels and replaces the second edition (ISO 19901-1:2015), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Clarification on the role of the metocean expert (Section 5.2 and Annex A.5.2)
— Additional information related to the determination of associated criteria (Section 5.3 and Annex A.5.3)
— Additional information related to the estimation of extreme/abnormal conditions (Section 5.7 and
Annex A.5.7)
— Alignment of the wind normative and informative sections with API RP 2MET (Section 7 and Annex A.7)
— Additional information related to breaking/non-breaking wave kinematic estimation (Section 8.4.3 and
Annex A.8.4.3)
— Expansion to section on additional environment factors to be considered (Section 10 and Annex A.10)
— Introduction of Normative and Informative text related to the verification of weather forecast information
(Sections 12 and Annex A.12)
— Update to Offshore Canada Regional Annex (Annex D)
— Update to Sakhalin/Sea of Okhotsk Regional Annex (Annex E)
— Update to Caspian Sea Regional Annex (Annex F)
— Introduction of Mediterranean Sea Regional Annex (Annex H)
— Introduction of Brazil Regional Annex (Annex I)
— Re-introduction of US Gulf of Mexico Regional Annex (Annex J)

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ISO/DIS 19901-1:2024(en)
— Re-introduction of Coast of California Regional Annex (Annex K)
— Re-introduction of Overview of Regions Excluding Gulf of Mexico and California Regional Annex (Annex J)
A list of all parts in the ISO 19901-1 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

vi
ISO/DIS 19901-1:2024(en)
Introduction
The series of International Standards applicable to types of offshore structure, ISO 19900 to ISO 19906,
constitutes a common basis covering those aspects that address design requirements and assessments of all
offshore structures used by the petroleum and natural gas industries worldwide. Through their application
the intention is to achieve reliability levels appropriate for manned and unmanned offshore structures,
whatever the type of structure and the nature or combination of the materials used.
It is important to recognize that structural integrity is an overall concept comprising models for describing
actions, structural analyses, design rules, safety elements, workmanship, quality control procedures and
national requirements, all of which are mutually dependent. The modification of one aspect of design in
isolation may disturb the balance of reliability inherent in the overall concept or structural system. The
implications involved in modifications, therefore, need to be considered in relation to the overall reliability
of all offshore structural systems.
The series of International Standards applicable to types of offshore structure is intended to provide a wide
latitude in the choice of structural configurations, materials and techniques without hindering innovation.
Sound engineering judgement is therefore necessary in the use of these International Standards.
The overall concept of structural integrity is described above. Some additional considerations apply
for metocean design and operating conditions. The term “metocean” is short for “meteorological and
oceanographic” and refers to the discipline concerned with the establishment of relevant environmental
conditions for the design and operation of offshore structures. A major consideration in the design and
operation of such a structure is the determination of actions on, and the behaviour of, the structure as a
result of winds, waves and currents.
Environmental conditions vary widely around the world. For the majority of offshore locations there are
little numerical data from historic conditions; comprehensive data often only start being collected when
there is a specific need, for example, when exploration for hydrocarbons is being considered. Despite the
usually short duration for which data are available, designers of offshore structures need estimates of
extreme and abnormal environmental conditions (with an individual or joint probability of the order of
−2 −3 −4
1 × 10 /year and 1 × 10 to 1 × 10 /year, respectively).
Even for areas like the Gulf of Mexico, offshore Indonesia and the North Sea, where there are over 30 years
of fairly reliable measurements available, the data are insufficient for rigorous statistical determination
of appropriate extreme and abnormal environmental conditions. The determination of relevant design
parameters has therefore to rely on the interpretation of the available data by experts, together with an
assessment of any other information, such as prevailing weather systems, ocean wave creation and regional
and local bathymetry, coupled with consideration of data from comparable locations. In particular, due
account needs to be taken of the uncertainties that arise from the analyses of limited datasets. It is hence
important to employ experts from both the metocean and structural communities in the determination
of design parameters for offshore structures, particularly since setting of appropriate environmental
conditions depends on the chosen option for the offshore structure.
This part of ISO 19901 provides procedures and guidance for the determination of environmental conditions
and their relevant parameters. Requirements for the determination of the actions on, and the behaviour of, a
structure in these environmental conditions are given in ISO 19901-3, ISO 19901-6, ISO 19901-7, ISO 19902,
ISO 19903, ISO 19904-1, ISO 19905-1 and ISO 19906.
Some background to, and guidance on, the use of this part of ISO 19901 is provided in informative Annex A.
The clause numbering in Annex A is the same as in the main text to facilitate cross-referencing.
Regional information, where available, is provided in the Regional Annexes B to I. This information has been
developed by experts from the region or country concerned to supplement the guidance provided in this
part of ISO 19901. Each Regional Annex provides regional or national data on environmental conditions for
the area concerned.
vii
DRAFT International Standard ISO/DIS 19901-1:2024(en)
Oil and gas industries including lower carbon energy —
Specific requirements for offshore structures —
Part 1:
Metocean design and operating considerations
1 Scope
This part of ISO 19901 gives general requirements for the determination and use of meteorological and
oceanographic (metocean) conditions for the design, construction and operation of offshore structures of all
types used in the petroleum and natural gas industries.
The requirements are divided into two broad types:
— those that relate to the determination of environmental conditions in general, together with the metocean
parameters that are required to adequately describe them;
— those that relate to the characterization and use of metocean parameters for the design, the construction
activities or the operation of offshore structures.
The environmental conditions and metocean parameters discussed are:
— extreme and abnormal values of metocean parameters that recur with given return periods that are
considerably longer than the design service life of the structure,
— long-term distributions of metocean parameters, in the form of cumulative, conditional, marginal or
joint statistics of metocean parameters, and
— normal environmental conditions that are expected to occur frequently during the design service life of
the structure.
Metocean parameters are applicable to:
— the determination of actions for the design of new structures,
— the determination of actions for the assessment of existing structures,
— the site-specific assessment of mobile offshore units,
— the determination of limiting environmental conditions, weather windows, actions and action
effects for pre-service and post-service situations (i.e. fabrication, transportation and installation or
decommissioning and removal of a structure), and
— the operation of the platform, where appropriate.
NOTE Specific metocean requirements for site-specific assessment of jack-ups are contained in ISO 19905-1, for
arctic offshore structures in ISO 19906 and for topside structures in ISO 19901-3.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.

ISO/DIS 19901-1:2024(en)
ISO 19900, Petroleum and natural gas industries — General requirements for offshore structures
ISO 19901 (all parts), Oil and gas industries including lower carbon energy — Specific requirements for offshore
structures
ISO 19902, Petroleum and natural gas industries — Fixed steel offshore structures
ISO 19903, Petroleum and natural gas industries — Concrete offshore structures
ISO 19904-1, Petroleum and natural gas industries — Floating offshore structures — Part 1: Ship-shaped, semi-
submersible, spar and shallow-draught cylindrical structures
ISO 19905-1, Oil and gas industries including lower carbon energy — Site-specific assessment of mobile offshore
units — Part 1: Jack-ups: elevated at a site
ISO 19906, Petroleum and natural gas industries — Arctic offshore structures
WMO-No 306, Manual on Codes
3 Terms and definitions
For the purpose of this document, the terms and definitions given in ISO 19900 and the following apply.
3.1
abnormal value
design value of a parameter of abnormal severity used in accidental limit state checks in which a structure is
intended not to suffer complete loss of integrity
Note 1 to entry: Abnormal events are typically accidental and environmental (including seismic) events having
−3 −4
probabilities of exceedance of the order of 10 to 10 per annum.
3.2
chart datum
local datum used to fix water depths on a chart or tidal heights over an area
Note 1 to entry: Chart datum is usually an approximation to the level of the lowest astronomical tide.
Note 2 to entry: Chart datum may differ from one chart to another and care is required if cross referencing sites that
are not on the same chart.
3.3
conditional probability
conditional distribution
statistical distribution (probability) of the occurrence of a variable A, given that other variables B, C, … have
certain assigned values
Note 1 to entry: The conditional probability of A given that B, C, … occur is written as P(A|B,C,…). The concept is
applicable to metocean parameters, as well as to actions and action effects.
EXAMPLE When considering wave parameters, A may be the individual crest elevation, B the water depth and C
the significant wave height, and so on.
3.4
design crest elevation
extreme crest elevation measured relative to still water level
Note 1 to entry: The design crest elevation is used in combination with information on astronomical tide, storm surge,
platform settlement, reservoir subsidence and water depth uncertainty and is derived using extreme value analysis.
Where simplified models are used to estimate the kinematics of the design wave, the design crest elevation may be
different from (usually somewhat greater than) the crest elevation of the design wave used to calculate actions on
the structure. In reality, the wave with the greatest trough-to-crest height and the wave with the highest crest will be
different waves.
ISO/DIS 19901-1:2024(en)
3.5
design wave
deterministic wave used for the design of an offshore structure
Note 1 to entry: The design wave is an engineering abstraction. Most often it is a periodic wave with suitable
characteristics (e.g. height H, period T, steepness, crest elevation). The choice of a design wave depends on:
— the design purpose(s) considered,
— the wave environment,
— the geometry of the structure,
— the type of action(s) or action effect(s) pursued.
Note 2 to entry: Normally, a design wave is only compatible with design situations in which the action effect(s) are
quasi-statically related to the associated wave actions on the structure.
3.6
expert
individual who through training and experience is competent to provide metocean advice
specific to the area or topic in question.
3.7
extreme water level
EWL
combination of design crest elevation, astronomical tide and storm surge referenced to either LAT or MSL
3.8
extreme value
representative value of a parameter used in ultimate limit state checks
−2
Note 1 to entry: Extreme events have probabilities of the order of 10 per annum.
3.9
gravity wave
wave in a fluid or in the interface between two fluids for which the predominant restoring forces are gravity
and buoyancy
Note 1 to entry: Wind-generated surface waves are an example of gravity waves.
3.10
gust
brief rise and fall in wind speed lasting less than 1 min
Note 1 to entry: In some countries, gusts are reported in meteorological observations if the maximum wind speed
exceeds approximately 8 m/s.
3.11
gust wind speed
maximum value of the wind speed of a gust averaged over a short (3 s to 60 s) specified duration within a
longer (1 min to 1 h) specified duration
Note 1 to entry: For design purposes, the specified duration depends on the dimensions and natural period of (part of)
the structure being designed such that the structure is designed for the most onerous conditions; thus, a small part
of a structure is designed for a shorter gust wind speed duration (and hence a higher gust wind speed) than a larger
(part of a) structure.
Note 2 to entry: The elevation of the measured gust should also be specified.

ISO/DIS 19901-1:2024(en)
3.12
highest astronomical tide
HAT
level of high tide when all harmonic components causing the tides are in phase
Note 1 to entry: The harmonic components are in phase approximately once every 19 years, but these conditions are
approached several times each year.
3.13
hindcasting
method of simulating historical (metocean) data for a region through numerical modelling
3.14
infra-gravity wave
surface gravity wave with a period in the range of approximately 25 s to 500 s
Note 1 to entry: In principle an infra-gravity wave is generated by different physical processes but is most commonly
associated with waves generated by nonlinear second-order difference frequency interactions between different
swell wave components.
3.15
internal wave
gravity wave which propagates within a stratified water column
3.16
Joint North Sea Project Spectrum
JONSWAP
version of the Pierson-Moskowitz spectrum which accounts for the continued development of the spectrum
through non-linear wave-wave interaction over time and space
3.17
long-term distribution
probability distribution of a variable over a long time scale
Note 1 to entry: The time scale exceeds the duration of a sea-state, in which the statistics are assumed constant
(see 3.35 short-term distribution). The time scale is hence comparable to a season or to the design service life of a
structure.
EXAMPLE Long-term distributions of:
— significant wave height (based on, for example, storm peaks or all sea-states),
— significant wave height in the months May to September,
— individual wave heights,
— current speeds (such as for use in assessing vortex-induced vibrations of drilling risers),
— scatter diagrams with the joint distribution of significant wave height and wave period (such as for use
in a fatigue analysis),
— a particular action effect,
— sea ice types and thickness,
— iceberg mass and velocity,
— storm maximum significant wave height.

ISO/DIS 19901-1:2024(en)
3.18
lowest astronomical tide
LAT
level of low tide when all harmonic components causing the tides are in phase
Note 1 to entry: The harmonic components are in phase approximately once every 19 years, but these conditions are
approached several times each year.
3.19
marginal distribution
marginal probability
statistical distribution (probability) of the occurrence of a variable A independent of any other variable
Note 1 to entry: The marginal distribution is obtained by integrating the full distribution over all values of the other
variables B, C, … and is written as P(A). The concept is applicable to metocean parameters, as well as to actions and
action effects.
EXAMPLE When considering wave conditions, A may be the individual crest elevation for all mean zero-crossing
periods B and all significant wave heights C, occurring at a particular site.
3.20
marine growth
living organisms attached to an offshore structure
3.21
mean sea level
MSL
arithmetic mean of all sea levels measured over a long period
Note 1 to entry: Seasonal changes in mean level may be expected in some regions and over many years the mean sea
level may change.
3.22
mean wind speed
time-averaged wind speed, averaged over a specified time interval and at a specified elevation
Note 1 to entry: The mean wind speed varies with elevation above mean sea level and the averaging time interval; a
standard reference elevation is 10 m and with an averaging time of 10 min. See also 3.11 gust wind speed and 3.46
sustained wind speed.
3.23
mean zero-crossing period
average period between (up or down) zero-crossing waves in a sea-state
Note 1 to entry: In practice the mean zero-crossing period is often estimated from the zeroth and second moments of
the wave spectrum as TT== mf()//mf() =2πωmm() ()ω .
z 20 20 2
3.24
monsoo
...