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Measurement of platform conductor preload in streamlining the life extensions of ageing offshore wells
HighlightsThis work explains the criticality of platform conductor assessment in ageing well integrity;.Conductor preload plays an important role towards calculation of preload stresses, in addition to the environmental and operating loads, and are commonly over-estimated;.Accurate prediction of the conductor preload will help streamline categorisation for repairs, potentially saving millions in premature repair cost and other resources for each well;.This work describes development of an ultrasonic based measurements of conductor preload, implementing the acoustoelastic method and time of flight (TOF) of the longitudinal critical refracted (LCR) wave component;.Laboratory tests are carried out to obtain specific material calibration curves, validated by numerical analyses, and can be used to obtain traditionally hard-to-determine axial preload value on conductors;.The proposed method has great potential in quantitative integrity assessment and reliable life extension activities for ageing wells located particularly in matured shallow water fields.
AbstractThe life extension of ageing oil wells is becoming an ever more crucial part of an operator's activities in recent years, mainly due to slumping oil price which discourages new exploration and the potential extended operation of some older fields with sufficient producing capacity still remaining. The conductor forms one of the primary structural components of wells and its deterioration over time warrants immediate integrity assessment and rehabilitation plans. The construction residual loading or preloads on the conductor are calculated as per standard guidelines and by analytical means during its design and installation phase, but may not be realistic when assessing aged conductors, due to the high levels of over-conservatism built in to address the various uncertainties during the well drilling phase, hence a more practical means of evaluating this residual load is required in carrying out the integrity assessments. This article presents the novel use of ultrasonic based non-destructive technique (NDT) to measure the conductor preload by observing the travel time of the longitudinal critical refracted (LCR) waves and employing the acoustoelastic method to determine the structural stresses. The measurement of the time of flight (TOF) of this wave component is evaluated from the signals measurement under a range of preload stresses induced into the specimen, and the acoustoelastic calibration curve is obtained as a result, for various section geometries and dimensions. Numerical analyses are also carried out to correlate and validate the magnitude order of the acoustoelastic constant of typical conductor steel grade (grade-B). These are in good agreement with each other and can be a very reliable tool for the on-site preload measurements during oil well integrity assessment. This measurement of conductor preload results in minimising any associated uncertainties, assumptions and the corresponding over-conservatisms carried over from the design stage, hence streamlining the repair and rehabilitation strategies to the most critical well-conductor groups in the field, thus significantly reducing the costs and resources for operators in extending life of aged wells.
Measurement of platform conductor preload in streamlining the life extensions of ageing offshore wells
HighlightsThis work explains the criticality of platform conductor assessment in ageing well integrity;.Conductor preload plays an important role towards calculation of preload stresses, in addition to the environmental and operating loads, and are commonly over-estimated;.Accurate prediction of the conductor preload will help streamline categorisation for repairs, potentially saving millions in premature repair cost and other resources for each well;.This work describes development of an ultrasonic based measurements of conductor preload, implementing the acoustoelastic method and time of flight (TOF) of the longitudinal critical refracted (LCR) wave component;.Laboratory tests are carried out to obtain specific material calibration curves, validated by numerical analyses, and can be used to obtain traditionally hard-to-determine axial preload value on conductors;.The proposed method has great potential in quantitative integrity assessment and reliable life extension activities for ageing wells located particularly in matured shallow water fields.
AbstractThe life extension of ageing oil wells is becoming an ever more crucial part of an operator's activities in recent years, mainly due to slumping oil price which discourages new exploration and the potential extended operation of some older fields with sufficient producing capacity still remaining. The conductor forms one of the primary structural components of wells and its deterioration over time warrants immediate integrity assessment and rehabilitation plans. The construction residual loading or preloads on the conductor are calculated as per standard guidelines and by analytical means during its design and installation phase, but may not be realistic when assessing aged conductors, due to the high levels of over-conservatism built in to address the various uncertainties during the well drilling phase, hence a more practical means of evaluating this residual load is required in carrying out the integrity assessments. This article presents the novel use of ultrasonic based non-destructive technique (NDT) to measure the conductor preload by observing the travel time of the longitudinal critical refracted (LCR) waves and employing the acoustoelastic method to determine the structural stresses. The measurement of the time of flight (TOF) of this wave component is evaluated from the signals measurement under a range of preload stresses induced into the specimen, and the acoustoelastic calibration curve is obtained as a result, for various section geometries and dimensions. Numerical analyses are also carried out to correlate and validate the magnitude order of the acoustoelastic constant of typical conductor steel grade (grade-B). These are in good agreement with each other and can be a very reliable tool for the on-site preload measurements during oil well integrity assessment. This measurement of conductor preload results in minimising any associated uncertainties, assumptions and the corresponding over-conservatisms carried over from the design stage, hence streamlining the repair and rehabilitation strategies to the most critical well-conductor groups in the field, thus significantly reducing the costs and resources for operators in extending life of aged wells.
Measurement of platform conductor preload in streamlining the life extensions of ageing offshore wells
Ramasamy, Ramesh (author) / Ibrahim, Zainah (author) / Chai, Hwa Kian (author) / Chau, Ting Fai (author)
Applied Ocean Research ; 65 ; 12-22
2016-11-24
11 pages
Article (Journal)
Electronic Resource
English
Platform Conductor Integrity Management in Life Extension of Ageing Offshore Wells
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