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An important aspect of deepwater well integrity is development of accurate conductor fatigue analysis due to cyclic loading during drilling operations. Fatigue damage in a structure occurs from stress changes in response to cyclic loading. In practice, the lateral cyclic soil response is typically modelled using Winkler lateral load-displacement (p-y) springs. However, recently developed soil models for conductor fatigue analysis are based on physical modelling in a geotechnical centrifuge. Notwithstanding the advantages of centrifuge modelling for investigating the conductor-soil interaction mechanism, development of simple laboratory tools to obtain p-y data directly from intact soil samples obtained from the field can also be very beneficial. This paper describes the development of a novel apparatus to obtain p-y and soil damping relationships from field samples specifically tailored for well conductor fatigue analysis. In addition, it compares test results obtained using reconstituted kaolin clay and intact natural Onsoy clay with centrifuge test results; ultimately demonstrating a satisfactory agreement between the two techniques. The results are highly encouraging and are believed to present a major step forward in deepwater well conductor fatigue analysis. The findings may also be beneficial to the offshore renewable energy sector. Key words: offshore well conductor, fatigue analysis, p-y curve, soil-conductor interaction, cyclic soil response, centrifuge modelling. Un aspect important de l'integrite de puits en eau profonde est le developpement de l'analyse exacte de la fatigue du conducteur en raison de la charge cyclique au cours d'operations de forage. Des dommages par fatigue dans une structure se produisent en raison de changements de contraintes en reponse a la charge cyclique. En pratique, la reponse lateral cyclique du sol est generalement modelisee a l'aide de ressorts charge laterale-deplacement (p-y) de Winkler. Cependant, des modeles de sol recemment mis au point pour l'analyse de fatigue de conducteur sont bases sur la modelisation physique dans une centrifugeuse geotechnique. Malgre les avantages de la modelisation par centrifuge pour l'investigation du mecanisme de l'interaction sol conducteur, le developpement d'outils de laboratoire simple pour obtenir des donnees p-y directement a partir d'echantillons de sol intact obtenu sur le terrain peut aussi etre tres benefique. Ce document decrit l'elaboration d'un nouveau dispositif pour obtenir p-y et les rapports d'amortissement du sol a partir d'echantillons preleves sur le terrain specialement adapte a l'analyse de la fatigue du conducteur de puits. En outre, il compare les resultats obtenus a l'aide de l'argile de kaolin et de l'argile Onsoy naturelle intacts reconstitues selon les resultats d'essais a la centrifugeuse; demontrant finalement un accord satisfaisant entre les deux techniques. Les resultats sont tres encourageants et nous pensons qu'ils presentent un grand pas en avant dans l'analyse de la fatigue du conducteur de puits en eau profonde. Les resultats peuvent egalement etre benefiques pour le secteur d'energie renouvelable en mer. [Traduit par la Redaction] Mots-cles : conducteur de puits en mer, analyse de fatigue, courbe p-y, interaction sol-conducteur, reponse cyclique du sol, modelisation par centrifuge., Introduction Deepwater oil and gas wells are drilled from anchored or dynamically positioned vessels (semi-submersible drill rigs and drillships). Exploratory and appraisal wells are drilled to determine the presence of [...]

The discusser quotes the mean value of HT ht when assessing method performance. • If a normalized stress term is defined as HT ht , then the ratio of the post-equalization term and the installation term is HT ht . 3 and 5 to HT ht values up to 142. [Extracted from the article]

This is the first of four companion papers that present a comprehensive assessment of the effect of sea floor subsidence on the Valhall complex of platforms. The study has included an estimate of the increase in platform failure probability as a function of increased subsidence. Subsidence raises the effective mean still water level and increases the potential for inundation of the deck for extreme storm conditions. Deck wave slam forces generate significantly greater platform loading and lead to: (a) higher levels of structural inelastic response and increased risk of structural failure as well as (b) water reaching the cellar deck, and hence affecting operators as well as equipment. The paper focuses on addressing the first of these two issues. A structural assessment study was performed to address the significance of present and future levels of subsidence on the safety of three North Sea platforms. The study included a systematic assessment procedure that addressed each of the factors that impacted structural integrity issues and reliability concerns. Such factors included: ultimate strength analysis methodologies, tubular joint formulations, group pile effects, and soil-structure interaction, which are described in this paper, as well as deck impact force formulations (Pawsey et al., 1998, 'Characterization of Environmental Loads on Subsiding Offshore Platforms,' 17th International Conference on Offshore Mechanics and Arctic Engineering, Lisbon, Portugal, July) component and system reliability modeling (Jha et al., 2000, 'Assessment of OffShore Platforms Under Subsidence--Part II: Analysis and Results,' ASME J. Offshore Mech. Arct. Eng., 122, pp. 267-273), and acceptance criteria (Stahl et al., 1998, 'Acceptance Criteria for Offshore Platforms,' 17th International Conference on Offshore Mechanics and Arctic Engineering, Lisbon, Portugal, July). This paper presents the assessment procedure, as well as the modeling approach. The paper also discusses the consequence classification of the three platforms and state-of-the-art soil mechanics techniques that lead to a significant increase in the tensile capacity of the foundation. [S0892-7219(00)00204-1]

Severe inherited factor VII (FVII) deficiency is a rare autosomal recessive disorder with a poor relationship between FVII coagulant activity and bleeding tendency. Both clinical expression and mutational spectrum are highly variable. We have screened for mutations the FVII gene of 37 unrelated patients with a FVII coagulant activity less than 5% of normal pooled plasmas. The nine exons with boundaries and the 5′ flanking region of the FVII gene were explored using a combination of denaturing gradient gel electrophoresis and direct DNA sequencing. This strategy allowed us to characterise 68 out of the 74 predicted FVII mutated alleles. They corresponded to a large panel of 40 different mutations. Among these, 18 were not already reported. Genotypes of the severely affected patients comprised, on both alleles, deleterious mutations which appeared to be related to a total absence of activated FVII. We suggest that this absence of functional FVII can explain the severe clinical expression. Whether a small release of FVII is sufficient to initiate the coagulation cascade and to prevent the expression of a severe phenotype, requires further investigations. European Journal of Human Genetics (2001) 9, 105–112. [ABSTRACT FROM AUTHOR]