Deepwater data analytics – asset monitoring at the edge

Thousands of kilometres of pipeline, flowline, and interconnecting spool pieces are installed on the world’s sea and ocean floors. They create vast networks and their design can be complex, having to account for a huge array of variables, from water depth to expected flow composition and behaviour.

The challenge

Sometimes, it’s not always possible to account for all of the variables that an oilfield infrastructure is subject to. This can lead to issues. External vortex induced vibration (VIV) or internal flow induced vibration (FIV), which can sometimes be caused by slugging. Slugging is created by variable or irregular flow of gas and fluids through risers, pipelines, flowlines or spool pieces.

These issues can cause problems for process equipment, impact production efficiency and, critically, accelerate pipeline fatigue. This has knock-on effects for design life. It can even cause pipelines to be displaced, entrenched or erode the supports they stand on.

When FIV occurs, pipeline engineers need all the information they can get about just how much this is happening and to what degree. This enables them to re-calculate the remaining fatigue life of the infrastructure and decide on the best remediation methods. Unfortunately, monitoring exactly what is happening – what forces the pipelines, flowlines or spool pieces are being subjected to – can be challenging, especially in deep water.

International subsea engineering company Oceaneering International Inc. was asked by an operator to solve this exact problem. They had a number of spool pieces deployed in more than 1,000 metres of water, running between riser bases and flowline termination assemblies. They were being subjected to sudden and frequent slugging movements.

These movements had already resulted in new spool piece supports having to be installed. The operator’s engineers needed to assess the resilience of the new supports and learn more about the vibration the spool pieces were encountering. The challenge was that no motion monitoring sensors had been fitted prior to commissioning. The solution would need to provide accurate and accessible data using a technique that was not cost-prohibitive to install and operate.

The solution

Oceaneering’s solution used an innovative, wireless approach with Sonardyne’s Subsea Monitoring, Analysis, and Reporting Technology (SMART) sensor as a key element of the project.

SMART sensors are, well, smart. They contain low-power MEMs-based (micro-electric mechanical systems) inertial measurement units (IMUs), subsea processing power and integrated acoustic modem capabilities. This means they can autonomously measure, log and process high-frequency, pipeline or spool piece acceleration and angular rate motion over pre-programmed monitoring intervals.

Importantly, SMARTs, which can be integrated with many different subsea sensors to suit a wide variety of applications, process data at source. This is then sent as small statistical summary packets of data – based on parameters set by the user – through the water column to a surface transceiver. This method reduces the need to send time-series, or raw, data up to the surface for analysis, which prolongs battery life, maximizes bandwidth availability and provides useful information to engineers faster. It’s edge analytics and subsea communication technology in one battery-powered autonomous compact unit. And it’s able to work on extended deployments down to 7,000 metres water depth.

For the high-frequency motion, SMARTS were installed on each spool piece at a location between the riser and flowline termination assemblies. To monitor lower frequency movement on one of the spool pieces, another Sonardyne technology was used: Autonomous Monitoring Transponders(AMTs).

AMTs are most commonly used for long-term survey and monitoring tasks where instruments are needed for acquiring acoustic ranges and sensor data without surface control. They time-stamp data and log it internally, to be retrieved when it’s needed at the surface.

By creating a Long BaseLine (LBL) array of “static” AMTs, to which “mobile” AMTs installed on a spool piece and fitted with sound velocity sensors can range, highly precise measurements of any horizontal movement of that spool piece can be monitored and logged. By fitting the mobile AMTs with Digiquartz pressure transducers, vertical motion could also be tracked accurately within the array.

Before installing the SMARTs and AMTs, Oceaneering surveyed the seabed location. This was done to determine the LBL array design and SMART and mobile AMT positioning. Oceaneering designed and built ROV-installable spool monitoring clamps. This allowed the SMARTs and AMTs to be easily attached to the spool pieces. For the LBL array, four AMTs were placed in tripod stands at predefined locations for optimal ranging.

Following installation, confirmation that all the SMARTs and AMTs were working and a post-installation survey, the autonomous and intelligent instruments were then just left to do their work. A huge benefit of both instruments’ design is that they can be left unattended for three years thanks to their internally monitored lithium primary cells.

Anyone with these instruments deployed in their field has a choice in how to collect the data generated. If it’s close to a topside facility, they can deploy a Sonardyne Dunker 6 transceiver permanently, via a deployment pole for the duration of the monitoring, or temporarily over-the-side, via a winch or A-frame.

If the subsea infrastructure is more remote, they could periodically send a support vessel or an unmanned autonomous surface vessel with a Dunker 6 to harvest the data. For this project, while the site was deep, it was close enough to the customer’s production facility. Oceaneering chose temporary deployments, using the Dunker 6 from an onboard crane, as and when data collection was required.

The results

Since commissioning in the summer of 2018, continuous SMART monitoring of the spools, at four-minute intervals has taken place. Packets of data from both SMART and AMT devices, including raw runtime data, have routinely been sent to the surface. Once received, it has been analysed and used in predictive modelling. This has enabled the operator to calculate the accumulated fatigue and remaining operational design life of their assets.

Gaining access to the spools’ motion characteristics has been invaluable to the operator. It’s data they would have been expensive to access through other means. It has led to a deeper understanding of each spool’s motion frequency, rotation angles and cycle times. Where previously the operator had concerns about the remaining operational life of the spools, they now know the operational life is within the limits of the productive life of the field.

This is a great result for the operator, but also for Oceaneering and Sonardyne. By working together we were able to find a cost-effective and viable solution for the operator and future customers with similar challenges. By combining our expertise and flexible instruments as an integrated solution, the supply chain is able to tackle operators’ deepest challenges, quite literally.

Precision depth monitoring for offshore operations

The Riser Profiling system can be used as a standalone, integrated within a Marksman LUSBL acoustic position reference system, or with a third-party integrated monitoring system.

6th Generation (6G®) DPTi or SMART transponders wirelessly mounted along the length of the riser, provide highly accurate data. These are clamped onto the riser during deployment or installed via ROV subsea. Up to ten transponders are mounted on a riser. Each transponder is fitted with the following sensors:

• High-resolution dual axis inclinometer
• Water temperature
• Pressure and depth
• Optional single point Doppler current meter (speed, direction)

The gathered data is transmitted wirelessly from the transponders using our Wideband 2 acoustic signals to a transceiver on the vessel, eliminating the need for expensive umbilical cables to fitted up each riser.

At a glance

• Designed for monitoring your riser’s integrity
• Helps prevent critical damage during operations
• Removes need for expensive cables
• 6G hardware and Wideband 2 acoustic delivers robust performance during operations
• User configurable update rates

Advanced monitoring for subsea success

Topside software makes changing monitoring regimes easy. You can even set an alarm to activate when the calculated riser angle exceeds a predefined limit.

At the update rate you choose, inclination, current speed and direction, pressure, temperature measurements are requested from each transponder. All data is processed, logged and displayed graphically and numerically on the topside computer software for your instant analysis. When SMART transponders are used, the data is processed within the transponder and wirelessly transmitted to the vessel’s transceiver.

Overview

When it comes to USBL and LUSBL transceivers, one model does not fit all situations and vessels. For Ranger 2 and Marksman installations, our High Performance Transceiver (HPT) is available two primary configurations.

HPT 5000
HPT 5000 offers full hemispherical acoustic coverage so it’s a popular choice for tracking multiple targets  (ROVs, AUVs, towfish, seafloor sensors) over a wide range of depths and elevations. The unit is also suitable for dynamic positioning reference on survey, research and offshore support vessels.

HPT 7000
HPT 7000 is engineered for ultra-deepwater operations, tracking targets far below (rather than to the side) of a vessel, and also high vessel noise operating environments, as those typically encountered on DP drilling and construction where aeration from thrusters is liable to cause signal interference.

Both models of transceiver fully support 6G LBL operations using Fusion 2 LBL software. They are also highly capable acoustic communications modems, able to interrogate, command and recover data payloads from deployed Sonardyne instruments including AMTs and Fetch. Supporting telemetry rates of up to 9,000 bps minimises the time a vessel has to wait on location to recover data, as well as supporting LBL operations.

HPT 5000/7000s are also available in Gyro USBL configurations offering calibration-free installation and use.

At a glance

• Use with Ranger 2 USBL and Marksman LUSBL systems
• Can also be used to communicate and harvest data from Sonardyne sensors
• Hemispherical (HPT 5000) or directional (HPT 7000) arrays to suit your vessel and application
• Can be deployed other-the-side, through-tube or through-hull
• Suitable for new-build vessels or USBL/LUBL upgrade for your existing vessel

All HPTs are built on our 6G technology platform with multi-element processing to enable transponders to be positioned more precisely, more quickly and more robustly due to improvements in signal processing algorithms and array design.

Functionality such as ‘Discovery Mode’ enables vessels equipped with Ranger 2 and Marksman to enter an offshore area and automatically detect previously deployed transponders (including their configured address and channel), making simultaneous operations using shared seabed arrays possible.

Manufactured in aluminium-bronze, HPTs are intended to be fitted temporarily or permanently to a vessel’s through-hull or over-the-side pole. HPT 5000s (including Gyro USBL 5000s) have also been fitted to large USVs for uncrewed missions controlled from over-the-horizon.

For specialist applications, inverted USBL, LMF frequency and extreme depth range HPT transceivers are also available. Please get in contact to discuss your requirements.