Successful Real Time Instrumentation Of The Conductor And Surface Casing Of An Exploration Subsea Well In The North Sea To Measure The Actual Loads Experienced During Drilling Operations

Myhre, Erling; Eilertsen, Lasse Eskil; Russo, Massimiliano; Johansen, Frank; Hart, Chris; Kalhovd, Tore Johannes

doi:10.4043/25770-ms

Cited by 6 publications

(1 citation statement)

References 1 publication

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“…Few studies evaluating the Zakeri et al (2015) model based on field data have already been reported in literature (Kannala et al 2016, Myhre et al 2015, Lindstad et al 2015. While the method proposed performs very well in predicting the wellhead fatigue damage from the model test, the reliability of the new method needs to be verified using field data collected during a drilling campaign.…”

Section: Introductionmentioning

confidence: 99%

Soil Model Assessment for Subsea Wellhead Fatigue Using Monitoring Data

Mercan¹,

Chandra²,

Campbell³

et al. 2017

Day 1 Mon, May 01, 2017

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A significant effort is made by the industry through analyses and field monitoring to ensure delivery of safe and reliable wells. Fatigue analysis is an important aspect of well integrity assurance. Structural fatigue damage arises from stress changes caused by environmental cyclic loads acting on the riser system. In practice, the conductor-soil interaction under cyclic loading is modeled using the soil resistance-displacement (P-y) springs. Use of an appropriate soil model is essential for accurate determination of the fatigue damage. The American Petroleum Institute recommendations (API 2011) for P-y curves, which are often used for conductor-soil interaction analysis, have originally been developed for piled foundation and are inappropriate for well fatigue analysis. To that end, a new approach was developed by Zakeri et al. (2015) to derive P-y curves specifically for well fatigue analysis. Ultimate performance of each soil model can be determined and verified with field monitoring. This paper presents results of a field monitoring campaign for a well drilled in 354 ft water depth within a complex seabed stratigraphy comprising sands (loose to dense) and clays (very soft to stiff). Design, calibration and verification of the riser/conductor structural model using field data are presented in a companion paper (Ge et al. 2017). Herein, the effect of soil modeling on wellhead fatigue is discussed and predictions made with the API (2011) and the Zakeri et al. (2015) soil P-y springs are compared to field monitoring data. For the case presented herein, the results indicate that the Blowout Preventer (BOP) stack motion response is significantly affected by the soil stiffness and modeling methods. The predictions made with the Zakeri et al. (2015) model provided BOP response similar to those observed in the field both above and below the mudline. Whereas, the analyses done with the API (2011) model significantly overestimated the 'measured' conductor fatigue life above the mudline and underestimated it below. The results of this monitoring program are a step forward in better understanding system behavior of offshore wells.

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Section: Introductionmentioning

confidence: 99%

Soil Model Assessment for Subsea Wellhead Fatigue Using Monitoring Data

Mercan¹,

Chandra²,

Campbell³

et al. 2017

Day 1 Mon, May 01, 2017

View full text Add to dashboard Cite

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Integrity Assessment of Offshore Subsea Wells: Evaluation of Wellhead Finite Element Model Against Monitoring Data Using Different Soil Models

Russo¹,

Zakeri²,

Kuzmichev

et al. 2016

Journal of Offshore Mechanics and Arctic Engineering

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Understanding well conductor–soil interaction mechanism plays an important role in well integrity assessment. Evaluation of field data obtained from monitored offshore wells can provide valuable insights into the matter. This paper presents a comparison of the numerical results obtained from a full three-dimensional (3D) finite element (FE) analyses model of the blowout preventer (BOP), wellhead (WH), conductor, and surface casing versus the field measured data obtained during drilling operations. Sensitivity studies were also performed for several parameters that were considered important in the local well response analysis under observed sea state conditions. The conductor–soil analyses were simulated using the Winkler spring p–y curves obtained by two different approaches: American Petroleum Institute (API) RP2GEO and a recently developed model by Zakeri et al. The results of bending moments in conductor and surface casing have indicated good agreement between FE model results and the field measurements.

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Learnings From Strain Measurements on an In-Field Conductor and Wellhead System

Shankaran

Rimmer

Haig

2018

Volume 3: Structures, Safety, and Reliability

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In recent years due to use of drilling risers with larger and heavier BOP/LMRP stacks, fatigue loading on subsea wellheads has increased, which poses potential restrictions on the duration of drilling operations. In order to track wellhead and conductor fatigue capacity consumption to support safe drilling operations a range of methods have been applied: • Analytical riser model and measured environmental data; • BOP motion measurement and transfer functions; • Strain gauge data. Strain gauge monitoring is considered the most accurate method for measuring fatigue capacity consumption. To compare the three approaches and establish recommendations for an optimal approach and method to establish fatigue accumulation of the wellhead, a monitoring data set is obtained on a well offshore West of Shetland. This paper presents an analysis of measured strain, motions and analytical predictions with the objective of better understanding the accuracy, limitations, or conservatism in each of the three methods defined above. Of the various parameters that affect the accuracy of the fatigue damage estimates, the paper identifies that the selection of analytical conductor-soil model is critical to narrowing the gap between fatigue life predictions from the different approaches. The work presented here presents the influence of alternative approaches to model conductor-soil interaction than the traditionally used API soil model. Overall, the paper presents the monitoring equipment and analytical methodology to advance the accuracy of wellhead fatigue damage measurements.

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Successful Real Time Instrumentation Of The Conductor And Surface Casing Of An Exploration Subsea Well In The North Sea To Measure The Actual Loads Experienced During Drilling Operations

Cited by 6 publications

References 1 publication

Soil Model Assessment for Subsea Wellhead Fatigue Using Monitoring Data

Soil Model Assessment for Subsea Wellhead Fatigue Using Monitoring Data

Integrity Assessment of Offshore Subsea Wells: Evaluation of Wellhead Finite Element Model Against Monitoring Data Using Different Soil Models

Learnings From Strain Measurements on an In-Field Conductor and Wellhead System

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