Location: Deepwater Gulf of Mexico, USA
Water Depth: Up to 160m
This project was an offshore trial conducted to test Welaptega’s 3D Modeling technology as applied to SCR FlexJoint inspection. The ultimate objective was to establish a means to better identify areas of concern, and to quantify any anomalies such that their progression can be tracked between subsequent inspections.
The trial took place on two SPAR facilities in the Gulf of Mexico. The FlexJoint is a steel-elastomer assembly designed to reduce motion-induced stresses in SCRs. The figure below shows a cross-section and installation drawing of a FlexJoint; notice the section labeled “Flex Element” in the cross-section drawing as this is the focus of the inspection work.
The trial was conducted using the Welaptega 3D Modeling system mounted on FlexJoint inspection skid, developed by Seanic Ocean Systems, and deployed via a work class ROV. Inspections were conducted on a 24-inch Oil Export riser and a 10-inch Gas Export riser. Anomalies found on in-service FlexJoints are typically either bulges or cuts/abrasions on the cover rubber stretched over the flex element. Anomalies in the cover rubber tend to indicate problems in the elastomeric flex element itself, which allows relative motion between upper and lower riser sections while preventing the release of hydrocarbons.
Figure 1: Cross-section and installation drawings of SCR FlexJoint (Courtesy of Lloyd’s Register)
Procedure
Welaptega’s 3D Modeling equipment (2-camera, 2-light array) was mounted in a custom designed frame to fit on the existing FlexJoint inspection tool operated by Seanic Ocean Systems. Figure 12, below, shows the equipment mounted to Seanic tool, situated on the riser extension below the FlexJoint.
Figure 2: Inspection assembly mounted to trial FlexJoint
As shown in the figure above, the Seanic tool (4) clamps to the riser and the camera-light assembly (3) is able to clock around the riser (2) capturing photos of the entire flex element (hidden within the FlexJoint Body {1}).
The following figure shows a screen shot of a 360° model processed from several dozen images taken in the onshore trial; the 12” riser is seen in the middle of the frame with the flex element, the black surface textured with circumferential rings, extending radially outward until meeting with the steel body of the FlexJoint.
Figure 3: 360° FlexJoint model (onshore trial)
To verify dimensional accuracy, rubber pads with anomalies of known dimensions were placed on the flex element and used to test the accuracy of the finished models. The following figure shows one such anomaly applied to the flex element, from which sub-millimeter accuracy was verified. In addition to planar measurements, cross-sections can be taken to measure depth of indentations and protrusions.
Figure 4: 3D model of simulated flex element anomalies to verify dimensional accuracy (onshore trial)
Successful offshore trials on two in-service FlexJoints were completed following the onshore trial. The now proven technology has been fully incorporated as part of the ongoing FlexJoint inspection initiative.
The 3D models will add value to FlexJoint inspection by quantifying anomalies and facilitating the tracking of the progression of anomalies over time. Additional inspection campaigns are planned for FlexJoints installed in the North Sea and West Africa.
