Buoyancy Design Eliminates VIV In High Currents, Minimizes Drag

A major milestone was successfully completed under the joint development agreement between Diamond Offshore Inc. and Trelleborg, which focuses on creation of a helically grooved buoyancy design with enhanced performance for drilling riser operations in high current conditions.

Test results revealed that when using the patented design vortex induced vibration (VIV) is effectively eliminated in high currents, with the added bonus that drag loading on the riser is also reduced to a level comparable with fairings, a press release stated. In June tow tank testing on the helically grooved design was performed in Trondheim, Norway. The extensive test program provided valuable hydrodynamic data confirming the design’s drag reduction and VIV suppression performance.

Fixed and dynamic drag coefficients of the new design were recorded during separate fixed and free vibration tow testing. Drag coefficients at an average of 0.65 were observed for relevant flow regimes, which is comparable to the performance of riser fairings. This is achieved through the highly successful VIV suppression of the design, effectively eliminating VIV response and subsequent drag amplification in the high excitation response range of offshore drilling risers. Forced motion testing of the helically grooved design was also performed to better understand excitation of the riser under high current conditions and for the development of lift coefficient data for use in analytical fatigue damage prediction programs.

The helical drag reduction and VIV suppression performance shows strong independence of current speed, which is consistent with the behavior of an external helical strake. However, the underlying flow physics causing the suppression are quite different, leading to the suitability of the helically grooved design for large diameter drill riser buoyancy.

Software Enables Data-driven Decisions To Improve Certainty

Baker Hughes, a GE company (BHGE), has released its CIRCA coiled tubing (CT) simulation software, which enables CT service providers to maximize equipment performance and improve operational efficiency in well interventions, a press release stated.

Based on learnings from the field and built and refined over three decades, the software allows CT providers and operators to build better job models for more predictable results. Operational guidelines for CT applications are typically based on experience rather than on hard data. Applying these methods in today’s more complex wells—particularly in unconventional wells with longer laterals and numerous stages—can compromise job performance and even damage downhole equipment.

Historically, CT simulation software has lacked real-world feedback and adequate support, producing inferior models that fail to adequately identify risks, especially in complex environments, the company said. The CIRCA software suite validates theoretical models with empirical data from the field to help CT providers move from experience-dependent operations to data-driven execution. The software delivers valuable insights into the subsurface, such as downhole conditions, flow rates and safe operating envelopes, enabling operators to calculate outcomes with more certainty to improve job planning and execution.

DNV GL Creates Remote Surveillance For Subsea Equipment Manufacturing

DNV GL developed a solution for remote surveillance service for subsea equipment manufacturing, a press release stated. The primary goal of this new alternative was based on cost savings; improved safety for surveyors; increased flexibility on testing schedules; availability of experts; and transparency for all stakeholders. Remote witnessing equips technicians with hardware and software that provide remote support or, depending on the type of test and its critical points, a standalone camera system that can be installed to increase savings and flexibility. At the local office, a DNV GL surveyor is connected to the technician delivering technical expertise in a timely manner.

—Staff Reports