ASPIRE for In Integrity Management Support for Upstream Assets Payam Jamshidi, TWI Ltd Sebastian Hartmann, Innospection Ltd
OVERVIEW - Discussion of corroded pipe assessment procedures under combined loading - What do we need? How we derived to assessment of conductors? - Current study and our approach - Assessment of well conductors - Some results - Conclusion
Objectives The ultimate objective of this project was to integrate the collection, management and analyses of inspection data for the purpose of providing RBI and repair decision making for upstream assets. This will be achieved by the following objectives: • To develop a customisable probabilistic based algorithm and software to use advanced reliability methods to assess failure scenarios for several types of non-standard geometries, loading, environment and operations; • To link the software to different NDT technologies to analyse the results seamlessly; • To validate the algorithm through pilot implementations on project partners’ identified cases. The ASPIRE TM - Project 760460 is funded by the EU under the Horizon 2020 Framework Programme
OIL IL & GAS ACCIDENTS - In the last 10 years, 34% of oil & gas losses happened in upstream ~ $12 billion The 100 Largest Losses 1974-2013, Large property damage losses in the Hydrocarbon Industry, 23rd Edition, MARSH
ASSETS SUBJECT TO COMBINED LOADING Engineering structures such as flexible risers, free-standing or top- tensioned rigid risers, and steel catenary risers are continuously subject to global bending moments in addition to axial loads and/or internal pressure. Global bending plays an important role when the assessment is applied to deep sea offshore pipes.
CORRODED PIP IPE ASSESSMENT - Pressure equipment used in the oil and gas industry is typically subjected to multiple loads (internal pressure, axial stress, global bending). - There are limited numbers of research programs addressing the assessment of corrosion defects in pipeline structures subjected to global bending, compressive loading or combination - Several methods for the assessment of corroded pipeline subjected to internal pressure loading are currently available; such as ASME B31G, DNV-RP-F101 RSTENGTH, API 579, etc. - These methods do not take into account the effect of global bending or longitudinal compressive load on the failure of the corroded structure and their predictions of failure pressure are quite conservative compared to the full scale tests*. Benjamin, A.C. (2013). “Prediction of the failure pressure of corroded pipelines subjected to a longitudinal • compressive force superimposed on the pressure loading”, The Journal of Pipeline Engineering , pp301.
Past Study at TWI - Assessment of LTAs in pipe structures subject to global bending and compressive loading and compares the results to the BS7910 reference stress solutions. - FEA is carried out to produce collapse loads of pipe structures containing corroded areas (with different LTA aspect ratios) subject to global bending, internal pressure, axial tension and ultimately combined bending and compression. - The model was calibrated against BS7910 under conditions of internal pressure and axial tension. - All models were analyzed to cover a wide range of LTA depth to pipe thickness ratios and aspect ratios so as to generate a closed-form or tabulated solution.
Past Study at TWI - The following depth to pipe wall thickness (B) ratios were analyzed: a/B = 0.3, 0.5 or 0.7 - The axial lengths given by c 1 /c 2 = 0.25, 0.5, or 1.0 The LTA was meshed densely whilst away from the LTA, the mesh was coarser.
Conclusion of f Past Study at TWI - The BS 7910 equations were conservative as would be expected. - In terms of total axial stress at failure, these analyses showed that compressive loads reduce the failure load; that the failure load is further reduced under combined loading, but that the BS7910 equations could still be used to provide conservative solutions (for all cases analyzed). - The failure criterion employed in this work has been validated extensively for internal pressure loads (and internal pressure with end cap axial forces). However, little experimental work has been done to verify the FEA failure criterion for other external load combinations and therefore experimental testing should be undertaken to verify the numerical procedures.
Well ll Conductors • Offshore well bores consist of several concentric tubes • The outermost well casing, the conductor, protects the inside casings from aggressive corrosion. • The conductor should not leak, nor buckle or collapse under both axial load and bending moment
Past Conductor Failures
Well Conductors • Purpose • To demonstrate / document viability & integrity of each of conductors • For next “x” years – Endorsement period – Time/Risk Based Inspection period • Avoiding any major repairs • Process • Review of available data • Design analyses and engineering assessments • Inspection scopes & results • Operational history including incidents 12
Assessment Procedure • Design check of well conductors is a stability check based on international best practices: • Petroleum and Natural Gas Industries, “Fixed Offshore Platform”, ISO -19902, 2007 • Institute of Petroleum, “Guideline for the Analysis of Jackup and Fixed Platform Well Conductor System”, 2001 • Design of Concentric Tubular Members, G. R. Imm, B. Stahl, Offshore Technology Conference, 1988. • Design Methodology for Offshore Platform Conductors, B. Stahl, M. P. Baur, Offshore Technology Conference, 1980. • Minimum Required Thickness (MRT) is the thickness below which the required cross sectional area is not achieved and failure may occur • Grouting in annulus of conductor and other internal casing/tubing will influence the MRT calculation. It will be in-conservative not to consider the effect of grouting.
Assessment Procedure In summary, design evaluation of conductors include: • Determine the equivalent section of the conductor by the supports configuration. • Determine the stiffness of the conductor based on effective length • Calculation of the axial loads and bending moment • Calculation of stress ratio MRT calculation which is the critical thickness at which the stress ratio is equal to 1.0 . Conductor Subjected to Axial, Internal and Bending Strength Stability Check Check Stress Buckling Design of Concentric Tubular Members, G. R. Imm, B. Stahl, Offshore Technology Conference, 1988.
Lo Loading Mi & M e Axial Compression P i & P e P i : - Axial load due to weight of conductor, internal casings etc. P e : - Axial load at each elevation due to weight on top of the conductor Global Bending M e : - Bending moment due to environmental condition such as “100 year storm – Wave and current” calculated by SACS software M i : - Bending moment due to eccentricity of casings
Effect of f Breathing Win indow - Breathing window in a section causes reduction in Area and consequently reducing the Second Moment of Inertia of that loading section. - Based on the size of each window (by using principles of mathematic and solid mechanic), reduction factors for Area and Moment of Inertia are multiplied in properties of the intact section.
Assessment Procedure
Assessment Procedure
MEC TECHNOLOGY - Operations - Little pipe preparation needed (no couplant) - Remote controlled deployment - NDE key points - up to 1.3” Wall Thickness, sensitive for isolated pit detection, sizing accuracy ≤ +/ - 10% - inspection through coatings (Neoprene etc.) & CRA layers (Monel, Inconel, TSA ) - inspection speed (net average run speed 0.25m – 0.5 m/sec) - separate C-Scan corrosion mapping of near side & far side or merged - Direct online data assessment & integrity assessing data set up Example field applications Conductor Scan Caisson/Riser scan Flexible Riser Scan
SPLASH ZONE INSPECTION Splash Zone Inspection & Assesment Support Riser / Caisson / Conductor -Combined cleaning & inspection -MEC & UT Technology combination -Inspecting through coatings -No operational interruptions - ROBOTIC TOP SIDE DEPLOYMENT & REMOTE CONTROLLED DRIVE Splash Zone
Remaining Lif ife Assessment SLOFEC Inspection Results Internal Indication External Indication (Marine corrosion zone) 1 Segment 1 The retirement thickness required to meet the loading Averaged Minimum 2 condition at each measured thickness segment of the from the SLOFEC results conductor (Splash zone) Segment 2 t MRT 3 mm ( i ) Distribution of RL RL (per segment) CR --- The remaining time to 4 exceed the Probability of Distribution of corrosion rate Failure (PoF) target will per segments based on be considered as the risk thickness data or corrosion (Sea Water zone) models based remaining life. Segment 3 5 Cumulative Distribution nom t Trd Function (CDF) CR age
Corrosion Rates Current Study Literature According to HSE Research Zones of corrosion for Steel Piling in Report 016 - Guideline for use Seawater of statistics analysis of sample Marine Zone inspection of corrosion Splash Zone Estimated CR will be the 95% confidence limit Source: F. L. LaQue, Marine Corrosion cause and Precention, P. 116, john Wiley & Sons, 1975. Reproduced by permission of The Electrochemical Society.
Recommend
More recommend
