Improved modeling leads to better riser design.

The advancement of offshore field developments into increasingly deeper water, coupled with the progressively more stringent safety requirements being placed on operators, has made the role of high-quality software in underpinning the engineering design and analysis process critically important. Today’s engineers rely on analytical capabilities to provide confidence in their designs and keenly desire a user-friendly interface to facilitate optimum productivity in relation to model creation and refinement.

Challenging the status quo

Existing software products used in the offshore industry broadly fall into two distinct categories, general purpose finite element packages and specialized tools tailored specifically toward the industry. While the former are undoubtedly powerful and all-encompassing, the myriad modeling options presented to the engineer make using these tools overly complicated, and efficient use of the software typically requires significant experience on the part of the engineer. Dedicated tools, on the other hand, rarely achieve an optimal balance between advanced analytical capabilities and user interface versatility.

The need for a better tool designed specifically for oil and gas operations was the catalyst behind recent improvements to a software product developed by MCS Kenny, Wood Group Kenny’s riser engineering and software solutions company.

Flexcom 8 is the company’s next-generation riser design and analysis software that delivers a step-change in how riser engineering design and analysis is performed. The enhancements provided by this new version lead to a better design that supports the industry’s increasing focus on improved process safety, better predictability, and greater knowledge of utilization and integrity during operations.

Flexcom 8 bridges the gap between finite element analysis and specialized industry tools. (Images courtesy of MCS Kenny)

Interface technology

The new user interface has been created using the latest software development technologies, including .NET Framework and Windows Presentation Foundation (WPF). The .NET Framework is an integral Windows component that supports the development of the most recent generation of applications. It includes a large library of functions and supports several programming languages, which allows developers to combine their own source code with the existing framework in an integrated development environment. WPF is a graphical system produced by Microsoft for rendering user interfaces in Windows-based applications. At its core lies a resolution-independent, vector-based rendering engine that is designed to take advantage of modern graphics hardware. Using these leading-edge technologies facilitated the development of the next-generation user interface.

Flexcom 8 represents a fully integrated engineering environment, with all of the necessary tools available “in one box.” A structural preview facility is available while model creation is in progress, which continually updates to reflect alterations and augmentations to the model. This affords an instantaneous preview of the structural configuration and distribution of elements, without the user having to undertake a full finite element analysis. The program also incorporates an automatic mesh-creation facility that expedites the model creation process during the initial stages of a project, allowing several sensitive studies to be carried out quickly and easily before the engineer decides on the optimal computational model.

Data specification is aided by useful input prompts, helpful tooltips, and automatic input data validation. If any constraints are violated, warning messages appear to alert the engineer. The program also is equipped with comprehensive context-sensitive help that provides instant access to descriptive information on every possible input parameter. These features combine to reduce the potential for error in input data specification.

The software is designed to simplify the quality assurance process. The hierarchy applied to the various input files within an entire project workspace is transparent so that all input file interdependencies are evident at a glance. Designated icons provide an indication of the status of each analysis, informing the user of successfully completed runs and highlighting any that require further attention.

For example, if any alterations are made to the model or loading, a status icon alerts the user that the results could be obsolete and potentially misleading. These features reduce administrative overhead, allowing engineers to focus on more technical aspects and design challenges.

A typical design scenario might involve combining various vessel offsets, current profiles, and wave sea states, such that a large load case matrix can quickly accumulate. With the new keyword parameterization facility, a single input file is capable of modeling a wide range of load case variations about a base model. The ability to retrieve analytical results also has been streamlined with the advent of an automatic post-processing interface to Excel and a collation facility that provides a useful means of assembling output data across a range of load cases into a central location. Naturally, such functionality delivers tangible benefits for engineering teams, making it faster and easier to compile input data and extract pertinent results.

The new software makes it easier to design complex subsea architecture.

Technical innovations, efficiencies

Significant technical enhancements also have been added to the software, including the areas of pipe-in-pipe modeling and internal fluid modeling. A sliding pipe-in-pipe contact model now available offers the advantage of more accurately modeling significant relative axial motion between the inner and outer pipes. This model is appropriate for a J-tube/flexible pull-in scenario, for example. Refinements also have been made to the internal fluid model so slug flow and the associated centrifugal forces can be captured accurately. This is particularly significant because the excitation of subsea components by slugs is an issue increasingly encountered by operators, and consequently, the requirement to consider slug loading now appears in many design specifications.

Several optimizations have been implemented in the finite element engine, resulting in increased computational efficiency such that Flexcom 8 has shown to be approximately 40% faster than its predecessor. Efficiency also has been improved significantly due to the elegant handling of multiple analyses. The software automatically determines the number of available licensed processing units on the local machine and endeavors to match this with the number of analyses in progress to ensure the optimum use of computational resources.

To provide users with the best possible combination of analytical tools, dual processing comes standard in Flexcom 8, and the frequency domain analytical capabilities are now freely available to the entire client base. Although frequency domain analysis is theoretically applicable only to systems with linear dynamic response, it can be a very useful screening tool for nonlinear systems as well. Where the technique can be employed, the computational effort is only a fraction of that required for a corresponding time domain simulation, resulting in huge savings in terms of run time.