Integrated Semi and Steel Catenary Risers (SCRs) in Deep Water and Harsh Environment Conditions

2006 ◽  
Author(s):  
G. Arnesen ◽  
J.I. Dalane ◽  
S.S.B. Aramanadka ◽  
K. Herfjord ◽  
R. Snell ◽  
...  
Keyword(s):  
Deep Water ◽  
Harsh Environment ◽  
Steel Catenary Risers

Steel Lazy Wave Riser Configuration for Turret Moored FPSO With Disconnectable Turret in Deepwater

2015 ◽  
Author(s):  
Daniel Karunakaran ◽  
Sankar Subramanian ◽  
Rolf Baarholm
Keyword(s):  
Deep Water ◽  
Cost Effective ◽  
Attractive Alternative ◽  
Harsh Environment ◽  
Detailed Case ◽  
Effective Manner ◽  
Water Developments ◽  
Pros And Cons ◽  
Steel Catenary Risers

Recently turret-Moored FPSOs have been used in many deep water developments worldwide, with consideration of disconnectable turrets for harsh environment applications. This trend makes the interactions between FPSO and risers system more important. Further, Steel Lazy Wave Risers (SLWR), which is a compliant variant of the mostly commonly used Steel Catenary Risers (SCR), is becoming an attractive riser option. The paper provides a review of the various riser systems that can be considered for turret-moored FPSOs, and specific emphasis on Steel Lazy Wave Risers. A detailed case study of Steel Lazy Wave Risers for a typical turret moored FPSO with disconnectable turret is presented. This system is described in terms of design and functionalities, the fabrication and installation methods are presented. The case study shows clearly that SLWR are an attractive alternative to be used for FPSO with disconnectable turret and is very efficient to fabricate and install in a very cost effective manner. Pros and Cons for SLWR are discussed, with consideration of the particular challenges of turret-moored FPSOs with large floater motions, hang-off geometry constraints at turret, hang-off loads, riser interferences, risers pre-installation, and turret disconnection constraints.

Strength and Fatigue Performance of Steel Lazy Wave Risers With Change in Configuration Parameters

2019 ◽  
Author(s):  
Mayank Lal ◽  
Feng Wang ◽  
Xiaohua Lu ◽  
Abhilash Sebastian
Keyword(s):  
Deep Water ◽  
Parametric Study ◽  
Fatigue Performance ◽  
Design Criteria ◽  
Cost Assessment ◽  
Fatigue Design ◽  
Design Variables ◽  
Steel Catenary Risers ◽  
Normative Cost ◽  
The Impact

Abstract Steel Lazy wave risers are being increasingly used for deep water applications due to better strength and fatigue performance in the touchdown zone compared to steel catenary risers. Several parameters govern the design of steel lazy wave risers including the length of the catenary from hang-off to start of buoyancy section and the length of the buoyancy section. In this paper, a parametric study is performed to investigate the trends in strength and fatigue performance of steel lazy wave risers with change in configuration parameters. A normative cost assessment is also performed to show the impact of these design variables on overall cost of the system. Dynamic analysis is performed to check the change in strength and fatigue performance of steel lazy wave risers as the configuration parameters are changed. The results from the parametric study will assist in designing steel lazy wave risers which satisfy the strength and fatigue design criteria.

Aasta Hansteen Subsea Production System for Deep Water and Harsh Environment

2019 ◽  
Author(s):  
Severin Lindseth ◽  
Elling Røsby ◽  
Brynjar Vist ◽  
Knut Axel Aarnes
Keyword(s):  
Deep Water ◽  
Production System ◽  
Harsh Environment ◽  
Subsea Production System

Optimisation of Steel Catenary Risers

2013 ◽  
Author(s):  
Per Erlend Voie ◽  
Nils Sødahl
Keyword(s):  
Objective Function ◽  
Deep Water ◽  
Large Diameter ◽  
Technical Solution ◽  
Field Development ◽  
Steel Catenary Risers ◽  
Fit For Purpose ◽  
Vital Component ◽  
New Applications ◽  
Mathematical Optimisation

The riser system is a vital component of deep water floating production installations. Field specific optimised solutions are generally required to obtain a technical solution fit for purpose and to secure an economic field development. In some cases, the riser system is a potential technology stopper preventing use of existing field proven floater/station keeping solutions for new applications. One such example is operation of large diameter steel catenary risers (SCR) from floating production units in harsh environmental conditions. This study is focused on methodology for optimisation of riser systems by use of a mathematical optimisation scheme. An optimisation problem may formally be described as minimisation of a function in several variables (objective function) subjected to additional constraints. For the first time the general optimisation framework Optima is outlined allowing for use of standard riser analysis software for evaluation of objective function and constraints. Principles for selection of objective function and constraints are discussed for practical design applications with reference to design codes. Finally, an optimisation study of a steel riser for deep water and harsh environment is presented.

A Parametric Study on Effects of Environmental Loadings on Fatigue Life of Steel Catenary Risers (Using a Nonlinear Cyclic Riser-Soil Interaction Model)

2010 ◽  
Author(s):  
Mehrdad Kimiaei ◽  
Mark Randolph ◽  
Ivan Ting
Keyword(s):  
Fatigue Damage ◽  
Deep Water ◽  
Interaction Model ◽  
Fatigue Assessment ◽  
Wide Range ◽  
Non Linear ◽  
Wave Heights ◽  
Steel Catenary Risers ◽  
Vessel Motion ◽  
Floating Platforms

Steel catenary risers (SCRs) are often the preferred option for subsea tie-back to floating platforms in deep water due to their conceptual simplicity, ease of construction and installation and simple interface with the flowlines. Fatigue design of SCRs, particularly in the touch down area (TDA), has always been one of the major engineering challenges. Traditionally, fatigue assessment of SCRs has usually been highly conservative, because of lack of precise understanding of the non-linear soil-riser-interaction in the TDA. Most fatigue studies are based on assumed linear stiffness for the seabed, partly because of the lack of robust non-linear riser-seabed interaction models and partly because the linear response simplifies the fatigue study. The recent availability of non-linear seabed response models provides an opportunity to improve fatigue assessment, but it is first necessary to evaluate how best to conduct fatigue studies for such nonlinear systems which can be sensitive to wide range of input parameters. This paper outlines a new advanced numerical model, considering nonlinear cyclic riser-soil interaction behavior, used to determine the contribution of different loading parameters on fatigue damage of SCRs in the TDA in deep water soft sediments. The main loading parameters considered are: different motions of floating vessels, wave heights, wave periods and wave packs ordering. Numerical modeling has shown that over 95% of the fatigue damage corresponds to floating vessel motion parallel to the riser axis at the connection point to the vessel. It is also shown that riser response at TDA is highly influenced with amplitude and period of the environmental loadings.

Riser Deployment and Hang-Off Analysis for a Harsh Environment, Deepwater Site

2004 ◽  
Author(s):  
Enda O’Sullivan ◽  
James N. Brekke ◽  
Michel Dib
Keyword(s):  
Decision Making ◽  
Deep Water ◽  
Drill String ◽  
Harsh Environment ◽  
Careful Attention ◽  
High Current ◽  
Retrieval Process ◽  
Heave Motion

In planning for a deepwater well, running/retrieval of a drilling riser in advance of rapidly developing seas was identified as a critical operation. The harsh seastates required careful attention to the well-specific operating criteria, (WSOC), or the metocean conditions that limit specific operations. Certain conditions would warrant the operation being shut down so that the riser could be pulled or run before conditions became excessive. In deep water, a running/retrieval operation can take several days and the consequences of being shut down part way can be severe. Moderately high current profiles can cause the riser to bind in the diverter housing, preventing further running or retrieval. If binding occurs, a dynamically-positioned vessel can carry out “drift running” operations to increase its operability. However, if conditions prohibit further running/retrieval, the riser may need to be hung off “hard” (with no compensation) at the drill floor or “soft” on the tensioners and/or drill string compensator. In such a case, in addition to large top riser angles, vessel heave motion can cause tension variation, depending on the hang-off conditions and the length of the deployed riser. This paper discusses how riser analysis was used to support the operational understanding of the riser running/retrieval process for this deepwater well. The results were used to assist in the planning and decision-making involved in drilling this well.

scholarly journals Feasibility Study of Selected Riser Concepts in Deep Water and Harsh Environment

2017 ◽  
Author(s):  
Gilang Muhammad Gemilang ◽  
Daniel Karunakaran
Keyword(s):  
Deep Water ◽  
Time History ◽  
Bending Moment ◽  
Harsh Environment ◽  
Steel Catenary Riser ◽  
Main Challenge ◽  
Large Motion ◽  
Touchdown Point ◽  
Heave Motion ◽  
Vessel Motion

One of the well-known riser systems, the Steel Catenary Riser (SCR), has been an attractive choice for the riser system in deep water. However, the main challenge of the SCR is large motions from the host platforms due to the harsh environment. The large motion of host platforms may induce excessive buckling and fatigue at the touchdown point. By screening the downward velocities at the hang-off point in the time history graph, the time at which the critical responses (i.e. buckling utilization, bending moment and compression) peak is identified. This study investigates the feasibility of the SCR configuration in terms of the capability to cope with the vessel motion. Several types of the SCR configurations are proposed in this study. The selected configurations of SCR in this study are conventional SCR, Weight Distributed SCR (WDSCR), and Steel Lazy Wave Riser (SLWR). The feasibility of the three riser configurations was analyzed in terms of strength and fatigue performance to understand the limitation of one over the other. The “lazy wave” configuration efficiently absorbs the vessel heave motions. Thereby the SLWR configuration is proven to be the most robust configuration to cope with large motion of the host platform. This study proves that although the SCR feasibility is limited due to vessel heave motion, innovative solutions can be established to extend its feasibility in order to cope with the vessel heave motion in harsh environment.

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