Dark networks and corruption: uncovering the offshore industry

Sub-seabed gas is commonly associated with seabed depressions known as pockmarks—the main venting sites for hydrocarbon gases to enter the water column. Sub-seabed gas accumulations are characterized by acoustically turbid or opaque zones in seismic reflection profiles, taking the form of gas blankets, curtains or plumes. How the migration of sub-seabed gas relates to the origin and distribution of pockmarks in nearshore and fjordic settings is not well understood. Using marine geophysical data from Loch Linnhe, a Scottish fjord, we show that shallow sub-seabed gas occurs predominantly within glaciomarine facies either as widespread blankets in basins or as isolated pockets. We use geospatial ‘hot-spot’ analysis conducted in ArcGIS to identify clusters of pockmarks and acoustic (sub-seabed) profile interpretation to identify the depth to gas front across the fjord. By combining these analyses, we find that the gas below most pockmarks in Loch Linnhe is between 1.4 m and 20 m deep. We anticipate that this work will help to understand the fate and mobility of sedimentary carbon in fjordic (marine) settings and advise offshore industry on the potential hazards posed by pockmarked seafloor regions even in nearshore settings.

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Reliability Analysis of Jack-Up Platforms Based on Fatigue Degradation

21st International Conference on Offshore Mechanics and Arctic Engineering, Volume 2 ◽

10.1115/omae2002-28360 ◽

2002 ◽

Cited By ~ 3

Author(s):

Naser Shabakhty ◽

Pieter van Gelder ◽

Hotze Boonstra

Keyword(s):

Service Time ◽

Great Part ◽

Fatigue Reliability ◽

Original Design ◽

Operational Conditions ◽

Stress Fluctuation ◽

The Difference ◽

Offshore Industry ◽

Jack Up ◽

Load Conditions

Generally, jack-up structures are used for production drilling and exploration of hydrocarbons. The combination of mobility and the behavior as a fixed structure in operational conditions has made it an important structure in the offshore industry over the last 40 years. When a jack-up structure has been in operation for a great part of its original design-life and intention is there to extend the usage of this structure at a specific location, an investigation on fatigue degradation of the structure is an essential factor that has to be carried out before taking any decision. Fatigue is the process of damage accumulation in material due to stress fluctuation caused by variation of loads in service time. The fatigue failure occurs when accumulated damage has exceeded a critical level. In this paper, the remaining fatigue capacity of the jack-up structure is considered as an indicator for adequate use of the structure. It can be specified based on the difference between design-fatigue and fatigue experienced by the structure. The design-fatigue can be determined based on fluctuation of loads during the lifetime of the structure and experienced fatigue is specified by the load conditions, which the structure has experienced during its service time. When the information on the load conditions which the structure has experienced in its service time is available or known precisely, determination of the remaining fatigue capacity could be carried out by using the Palmgren–Miner’s rule. In practice, uncertainties are present in loads and characteristics of material. Hence it will be reasonable to determine the remaining fatigue reliability of the structure by the reliability methods. In this paper, based on a crack propagation approach and achieved information from inspection, it is shown that the remaining fatigue reliability of jack-up structures could be determined and updated by using a Bayesian procedure in the duration of the service time.

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Free-Surface Flow Simulations With Interactively Moving Bodies

Volume 2: Prof. Carl Martin Larsen and Dr. Owen Oakley Honoring Symposia on CFD and VIV ◽

10.1115/omae2017-61175 ◽

2017 ◽

Author(s):

Arthur E. P. Veldman ◽

Henk Seubers ◽

Peter van der Plas ◽

Joop Helder

Keyword(s):

Free Surface ◽

Free Fall ◽

Free Surface Flow ◽

Surface Flow ◽

Numerical Solution Method ◽

Flow Simulations ◽

Floating Object ◽

Offshore Industry ◽

Floating Objects ◽

Moving Bodies

The simulation of free-surface flow around moored or floating objects faces a series of challenges, concerning the flow modelling and the numerical solution method. One of the challenges is the simulation of objects whose dynamics is determined by a two-way interaction with the incoming waves. The ‘traditional’ way of numerically coupling the flow dynamics with the dynamics of a floating object becomes unstable (or requires severe underrelaxation) when the added mass is larger than the mass of the object. To deal with this two-way interaction, a more simultaneous type of numerical coupling is being developed. The paper will focus on this issue. To demonstrate the quasi-simultaneous method, a number of simulation results for engineering applications from the offshore industry will be presented, such as the motion of a moored TLP platform in extreme waves, and a free-fall life boat dropping into wavy water.

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Use of accident precursor event investigations in the understanding of major hazard risk potential in the Norwegian offshore industry

Proceedings of the Institution of Mechanical Engineers Part O Journal of Risk and Reliability ◽

10.1177/1748006x12468670 ◽

2012 ◽

Vol 227 (1) ◽

pp. 66-79 ◽

Cited By ~ 3

Author(s):

Jan-Erik Vinnem

Keyword(s):

Present Article ◽

Risk Indicator ◽

Specific Requirement ◽

Hazard Risk ◽

The Us ◽

Objective Risk ◽

Major Accident ◽

Offshore Industry ◽

Accident Precursor ◽

Risk Potential

The recent offshore accidents at the Macondo and Montara fields in the US and Australia have demonstrated the importance of learning from major accident precursors in order to appraise the risk potential involved in critical offshore operations. This is fully realised by the Petroleum Safety Authority in Norway, which has a specific requirement for such learning in its regulations. However, an unfortunate practice has been developed by the major players in the Norwegian offshore industry, whereby potential is severely and systematically downplayed, probably to limit the negative exposure if the actual potential consequences were known. The present article analyses 45 major accident precursor investigations in order to demonstrate the effect of downplaying the potential of major accidents. It demonstrates how the risk potential classified in investigation reports has a random relationship to the more objective risk potential, as shown in the national risk indicator project conducted by the Petroleum Safety Authority. This is further demonstrated by comparing company investigations with authority investigations in four cases where parallel investigations were performed.

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Safety aspects of HV machines in the offshore industry

10.1049/ic:19970316 ◽

1997 ◽

Author(s):

T.R. Thompson

Keyword(s):

Safety Aspects ◽

Offshore Industry

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BS 7910: History and Future Developments

Volume 1: Codes and Standards ◽

10.1115/pvp2009-78057 ◽

2009 ◽

Author(s):

Isabel Hadley

Keyword(s):

Assessment Methods ◽

Weld Strength ◽

Assessment Procedure ◽

Metallic Structures ◽

History Of ◽

Fracture Assessment ◽

Offshore Industry ◽

Crack Tip Constraint ◽

The Uk ◽

Assessment Procedures

BS 7910, the UK procedure for the assessment of flaws in metallic structures, was first published almost 30 years ago in the form of a fracture/fatigue assessment procedure, PD6493. It provided the basis for analysing fabrication flaws and the need for repair in a rational fashion, rather than relying on long-established (and essentially arbitrary) workmanship rules. The UK offshore industry in particular embraced this new approach to flaw assessment, which is now widely recognised by safety authorities and specifically referred to in certain design codes, including codes for pressure equipment. Since its first publication in 1980, PD6493/BS 7910 has been regularly maintained and expanded, taking in elements of other publications such as the UK power industry’s fracture assessment procedure R6 (in particular the Failure Assessment Diagram approach), the creep assessment procedure PD6539 and the gas transmission industry’s approach to assessment of locally thinned areas in pipelines. The FITNET European thematic network, run between 2002 and 2006, has further advanced the state of the art, bringing in assessment methods from SINTAP (an earlier European research project), R6, R5 and elsewhere. In particular, the FITNET fracture assessment methods represent considerable advances over the current BS 7910 methods; for example, weld strength mismatch can be explicitly analysed by using FITNET Option 2, and crack tip constraint through Option 5. Corrosion assessment methods in FITNET are also more versatile than those of BS 7910, and now include methods for vessels and elbows as well as for pipelines. In view of these recent advances, the BS 7910 committee has decided to incorporate many elements of the FITNET procedure into the next edition of BS 7910, to be published c2012. This paper summarises the history of the development of BS 7910, its relationship with other flaw assessment procedures (in particular FITNET and R6) and its future.

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