Stress Engineering Services (SES) has delivered a state-of-the-art real-time drilling riser and wellhead monitoring system (RFMS), in conjunction with its Condition Based Maintenance (CBM) process for Noble Corporation’s ultra-deepwater drillship Noble Tom Madden.
The RFMS provides dynamic subsea measurements with a high degree of reliability for the drilling riser and wellhead systems. By precisely recording the motion of the drilling riser, wellhead and casing system at discrete points in a time synchronous manner, fatigue damage of these components are determined and actionable information on the health of the drilling riser, wellhead and casing system can be delivered to the rig crew.
SES’s CBM process supports structural integrity evaluation and maintenance assessments of drilling risers to assess the condition of drilling riser joints, determine when important components will need service or replacement and assess the remaining life of the component. This process is function-based on a tailored period, rather than time-based, improving performance economics for operators throughout the industry. For this project, a life cycle CBM system will be deployed and performed on the MODU.
Chuck Miller, V.P., Stress Engineering Services, said, “Our ABS-qualified CBM process will remove uncertainties surrounding damage of the riser joints. We are proud that our CBM process and RFMS technology arms drilling engineers with innovative automation, digitalization and data analysis techniques and empowers them to make more informed decisions.”
Orlan Lyle, director-worldwide subsea & maintenance, Noble Drilling Services Inc., said, “Using SES’s CBM process together with their RFMS technology will allow us to make data driven decisions concerning the condition of our assets. The associated insight helps us focus on safety, identify measurable risks, manage our economics with actionable data and ultimately provides us with better information on the health of our assets.”
Realtime Fatigue Monitoring System (RFMS)
Stress Engineering Services developed the Realtime Fatigue Monitoring System (RFMS0) as a method of providing field measurements of stress and fatigue on drilling risers, wellheads and other subsea systems in near real time.
The RFMS significantly advances riser integrity management by
Using measured data at a fewer locations
Using advanced algorithms to reconstruct stress and fatigue damage along the entire riser
Integrating this approach into a fully automated, real-time environment
The RFMS provides a basis for understanding all the fatigue loads on a wellhead system. The wellhead is the last pressure barrier between the well and the environment. Understanding the loads and managing the loads on the system ensures that the integrity of the system is not compromised, and protects the environment from any potential discharge of hydrocarbons. As a result, drilling engineers are empowered with a tool that provides real-time data on the integrity of the drilling riser, enabling informed decisions to be made in adverse environments that increase safety and efficiency of drilling operations.
The RFMS can also significantly reduce downtime with commensurate cost savings. The real-time stress and fatigue information provided by the RFMS will prove increasingly useful as riser design boundaries are extended, and as structural integrity management becomes a preeminent concern in deepwater drilling and production operations. Ultimately, a sufficient amount of quality field data are expected to lead to improved model validation and simulation accuracy, and a more focused inspection and integrity management program.
The RFMS calculates stress and fatigue at any location in a riser system/wellhead/conductor casing via measurements from 5-10 accelerometers and angular rate sensors placed at strategic locations along the riser, along with analytical riser mode shape information. Since the only required online inputs are the dynamic riser response, top tension, and mud weight, fatigue estimates may be calculated without knowledge of the impinging currents or other forcing events. Vibration sensors and data acquisition electronics are housed in Subsea Vibration Data Logger (SVDL). The SVDL units are connected via fiber optic subsea cabling to a central data acquisition system, located topside. Data from each SVDL is displayed as it is acquired, and processed with a
sophisticated online computer algorithm to synthesize stress estimates along the entire riser length using a database of riser dynamic modes. The estimates are then processed chronologically via rainflow counting, recording fatigue damage accumulated during the deployment. The fatigue estimates are updated at 15 minute intervals, thereby providing actionable information to the drilling crew in real-time.
Life Cycle Condition Based Monitoring (CBM) for Drilling Risers
The Laser Profilometry Bore Erosion Measurement and Inspection System (BEMIST”‘) has been used extensively by the Dept. of Defense and NASA. The scanner head rotates at 250 rpm, collecting more than 3000 points of measurement in each rotation, producing a high resolution internal map of the component surface. Laser ID measurements are collected on the inner diameter of the main bore and auxiliary lines, between wells to characterize the state of drilling riser joints. The system generates millions of high resolution data points, which are harnessed and analyzed using LaserViewer software toaccurately map and determine material loss, characterize features to determine method of causation and perform detailed dimensional analysis of the entire tube. A report summarizing the anomalies that meet the criteria are identified and measured, along with the location of the feature on the tube.
The system determines stress and fatigue at any location in a riser system/wellhead/conductor casing with vibration sensors and data acquisition electronics housed in a Subsea Vibration Data Logger (SVDL). The data is processed using state-of-the-art SES patented technology, designed to provide the drilling crew with critical, actionable information.
The SVDL can be installed individually by an ROV on riser joints, wellheads and BOPs in `offline’ mode, where the recorded vibration data is retrieved after the measurement campaign, (which can last several weeks), and processed offline to estimate stress and fatigue. The operator is provided with a useful tool to assess system integrity at any time during a drilling campaign. After the drilling riser joints have been recovered to the surface, the LaserStream BEMIS is used to inspect them. The BEMIS is deployed through the ID of the riser via a tethered crawler. This data is collected while the riser is on the deck and eight joints can be inspected in one day, with the field results being available at the site, and a final report following in a week.
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