Market forecasts point to a gradual revival of offshore project activity in 2021 following this year’s widespread postponements. But with oil price volatility set to continue, production system providers will be pressed to demonstrate measures in their tenders for suppressing opex costs, along with high levels of safety and performance including facility uptime.
Digital twin technology is playing a part in this process, and one firm advocate is Bluewater Energy Services, which is pursuing a redeployment of its FPSO Glas Dowr. Since undergoing a conversion from a newbuild oil tanker in the mid-1990s, the vessel has operated on three fields in different parts of the world, in harsh to moderate conditions.
This summer, the company appointed Lloyd’s Register (LR) to develop a ‘structural digital twin’ model of the FPSO, using its proprietary cloud-based technology to determine global and fatigue hull strength for a redeployment in various potential geographical locations. The project involves integration of multi-physics models with the vessel’s historical sensor and design data to ‘mirror’ and thereby predict the status and lifespan of the corresponding ‘physical twin’ (Glas Dowr). Bluewater aims to use the results to predict the vessel’s structural performance at the new field location prior to the deployment.
The digital twin will be designed to collect and process sensor data continuously, delivering a constantly evolving picture of the vessel’s condition that Bluewater can use to assess its health status. In the project’s current first phase, LR is using the structural digital twin to run operating scenarios and historical simulations, based on design, historical measurements, and operational data from the three field deployments to date. The second phase will involve LR performing redeployment evaluations based on future operational scenarios, drawing on findings from a structural integrity assessment.
Glas Dowr was the fifth FPSO in Bluewater’s fleet. Unlike its four predecessors – all conversions of second-hand oil tankers – the vessel was a newbuilding under construction in Japan in 1995 for a tanker owner. Bluewater put in a successful counter-offer, sailing the completed tanker under its own propulsion to the Harland & Wolff shipyard in Northern Ireland for conversion to a steel-hulled FPSO.
Following an initial short-term assignment for Amerada Hess in the late 1990s on the Durward/Dauntless fields in the UK central North Sea, Bluewater transferred the vessel to South Africa for a second conversion in preparation for a re-deployment on the Sable field for Soekor E&P in the South Atlantic. Modifications to the topsides included installation of additional gas compression and process separation modules.
Following this second field assignment, which ran from 2003 to 2008, the company commissioned a third re-fit at the Sembawang Shipyard in Singapore, in readiness for a third deployment in late-2011 at the Eni-operated Kitan field 500 km (310 mi) offshore in the Joint Development Area of the Timor Sea, between Timor-Leste and northwest Australia. Operations ceased around four years later.
In its current incarnation, Glas Dowr is 242 m (794 ft) long with a breadth of 42 m (138 ft), a deadweight of 89,384 t, 7,985 sq m (85,950 sq ft) of deck space, and accommodation for 80 personnel. It has capacity to process 60,000 b/d of crude and storage for up to 660,000 bbl, with further modules for crude stabilization, produced water handling, water injection, gas compression and dehydration, and a combination of gas turbines and diesel generators for power.
The vessel is said to be designed and proven to operate in harsh and mild environments with high uptime, and in compliance with strict regulatory and safety regimes. Bluewater sees scope for re-use on most fields throughout the world, including the North Sea.
The company embarked on its own digital twin initiative for its FPSO fleet in the late 1990s, as Peter Burger, VP Technology explained. “We began by digitally connecting design, vendor, and as-built documents with equipment tags and maintenance records to create a near real-life data-set. At that point in time it was mainly focused on supporting the offices and offshore crew with finding original data and maintaining the best possible truth of as-built and as-modified data.
“However, a decade later, with assets in operation and modified for relocation or to suit field changes, we started to see the benefits of technological advances such as physical scanning and links with maintenance logs. In addition, new HSE and European directives led to the connection of more records and certificates of both green and brownfield projects which needed to be maintained for the operating asset.
“The term ‘digital twin’ is a buzzword used by many and has many different meanings and interpretations. For Bluewater, the priority is to connect our existing information sources dynamically to act as a near-real life, virtual image of an asset, helping to improve operational performance and efficient execution of asset modifications.”
At present the company is working on four associated initiatives. The first involves use of latest-generation 3D laser scanning to create or renew Point Cloud models of the FPSO topsides process plant. “This model is converted to 3D CAD visualization models that our engineering teams can use for design of modifications to, for instance, piping systems, new equipment or mechanical handling routes,” said Peter van Sloten, Department Head Technology at Bluewater. “Use of this technology has already brought cost savings as we could dispense with offshore surveys, and the modification went way easier and faster than the alternative of combining photos, offshore measurements, and 3D CAD design models.”
A second area under expansion is remote monitoring from shore through the creation of a digital twin of the FPSO’s onboard integrated control and safety system. “In future,” van Sloten said, “this may lead to further lowering of manning levels on the FPSO and reduced opex: we are already targeting a skeleton crew with various monitoring and preventive activities managed from shore. There are a large number of sensors throughout an FPSO, and the data they generate are collected and analyzed. We then seek to establish trends via further data analysis and over time through the use of artificial intelligence, leading to proactive measures as well as lengthening inspection and maintenance intervals. Although this monitoring has not as yet brought measurable savings, we do have good expectations of the benefits.”
The third branch of the campaign is LR’s Structural Digital Twin (SDT) for the Glas Dowr, which will create a detailed FE model of the FPSO’s hull. “With the use of historic hull, sensor and weather data, we can determine the residual (fatigue) lifetime of the hull,” van Sloten continued. “The SDT twin will also support and complement risk-based inspection, and could lead to a reduction in inspection work and planned downtime. We believe digital twins could, as an example, reduce the number of tank inspections and thereby lower inspection costs. For future redeployments of the FPSO, the SDT can be used to analyze potential fatigue damage and to determine any repair/modification scope required for the hull structure in order to meet the desired future lifespan. We see this development as an investment that can yield future savings.”
“Since the Glas Dowr’s first conversion in the mid-1990s,” Burger added, “it has been instrumented with a unique set of sensors to monitor the hull stresses and motions caused by waves and changing load conditions. This formed part of a joint industry project called Monitas involving a few FPSO companies from frontier owner/operators such as Bluewater, oil majors, and others. These data sets appear to be of great value for redeployments in view of hull strength and fatigue loading. Apart from the hull monitoring, the instrumented topsides and marine systems are also being maintained as a near real-life ‘virtual vision’ with the associated data.”
Bluewater’s fourth digital ‘thrust’ focuses on the use of tablet computers outdoors: this has yielded benefits in the construction and commissioning phases of recent projects, and during operations and maintenance.
According to Luis Benito, Innovation and Co-Creation Director at LR, “in our view, digital twin technology, if used as an integral part of the decision-making process, can improve an FPSO operator’s competitive advantage. Benefits can include revenue protection, increased operational efficiency, and better customer experience as the technology gives the operator’s client increased transparency on the asset’s ability to remain productive. This can help operators establish safer operations through embracing recommendations based on insights drawn from past behavior across the fleet – and that in turn gives operators greater confidence in human-based operations as it can potentially lessen the chances of human errors occurring.
“LR’s structural digital twin solution for FPSOs offers a way to monitor and control a unit’s inspection, maintenance, and repair (IMR) activities and processes by using in-service data for safer and economic operations. It provides real-time insights for implementation of a data-driven classification and compliance regime which would enable IMR based on real-time data and focused, risk-based inspection. When combined with remote and robotics technologies, the digital twin reduces the need for human intervention in offshore operations, ultimately ushering the industry towards its progressive de-manning mission, meaning that personnel can be deployed to support remote operations onshore.”
“The digital twin model for the Glas Dowr is trained on historical data from the vessel’s past performance. It also takes into account the initial and subsequent two redeployment upgrades as well as historical inspection data in order to achieve a reliable future prediction based on future operational scenarios chosen by Bluewater,” said Vaibhav Parsoya, LR’s Intrapreneur – Digital Solutions Innovation, Marine & Offshore. “The outcome of the twin would be to help Bluewater understand its probable remaining useful life under given future scenarios, allowing the company to determine the modification scope, if any is required for the chosen design life and future field deployment. The twin would continue to guide operational decisions following the vessel’s redeployment in order to regularly evaluate its structural performance and support maintenance and inspection activities while in service.”
Burger added: “The LR model will be used to assess various scenarios and in particular for the harsher environments like the North Sea. This includes any type of redeployment, from extended well testing for early production purposes up to full-field developments.”
As the digital twin is built, maintained and trained using real-time data, and evolves its predictions over time, it should start to reduce the volume of inspection/survey activities by switching the focus to critical areas. Those physical inspections, Benito explained, can instead be undertaken by remote technologies that feed the data to the ‘twin.’ “Then, through factoring the inspections data into predictions, the twin should reach a level of fidelity that gives confidence to our surveyors on the likely levels of risks, without the need for a physical visual inspection – making regular surveyor checks on-board the asset a thing of the past.
“This is a highly innovative project which is challenging the status quo of how things are done at present, and LR believes it could be a critical milestone for the offshore industry’s digital transformation. For this reason, we have a dedicated full-time team based in several countries comprising digital, engineering and offshore specialists supported by engineering and operations specialists from Bluewater. We expect to achieve our first major milestone before the end of this year.”
“At the same time,” Parsoya added, “it is a novel technology for the offshore and marine industries, so lessons are being learned throughout the process. It is important, therefore, to identify what type and quality of data would be required, keeping in mind the specific business and/or engineering challenges that need to be resolved before exploring Big Data or Digital Twin technologies. The next step should be to increase the quality of data over time, building a collection of ‘compatible data’ for the individual challenge being addressed. Thanks to Bluewater’s proactive recognition of the value of data and measurements in engineering and operations, Glas Dowr has an extensive library of data from its operations over two decades, and this has been key to our learnings so far.”
According to Burger, “the present co-operation with LR is intended to extend the FPSO’s future operations offshore. Likewise, and when the foreseen operational cost savings become evident, Bluewater may extend the co-operation to some of its other assets. Today we connect several platforms to our virtual asset image: from design to real-life sensor data and health diagnostics, delivered by OEMs and ICSs. Data integrity is vital but with digital twin investments, both time and expense can easily become excessive and at the same time the industry’s expectations of the benefits are high, perhaps too high.
“Common sense remains paramount in the quest to enrich existing (big) data with smart data, although we do believe that not all the benefits of digital twins are tangible. Nevertheless, pro-active remote monitoring and data intelligence conducted by data analysts or artificially should lead to further increase in efficiency, uptimes, and reduced operational costs and emissions. Bluewater has seen the benefits for EPC projects during operations, and also the benefits of being both developer and owner-operator.”