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Prislin I.,BMT Scientific Marine Services Inc. | Chabot L.,Murphy Oil Co. | Dean L.H.,BMT Scientific Marine Services Inc. | Liu T.,Offshore Technology LLC | Ye W.,Offshore Technology LLC
Proceedings of the Annual Offshore Technology Conference | Year: 2014

The paper describes a reliable, effective, and practical, solution for monitoring the integrity of the "soft lashing" mooring lines connecting a Tender Assist Drilling rig (TAD) to the Kikeh Dry Tree Unit (DTU) and alerting operators the need to replace the mooring lines prior to failure due to fatigue damage. The solution is based on a ton-cycle method that measures cumulative line tension and calculats number of wire over sheave bending cycles due to the lashing line entering and exiting the DTU turn down sheave. The endurance limit of the sheave wire was calibrated by analyzing recorded dynamic line tension data of a lashing line that failed unexpectedly in service. The lashing line ton-cycle method has been integrated with the other marine and structural monitoring parameters on board the Kikeh DTU for several years. The cumulative ton-cycle of each soft lashing line is displayed on the marine operator's console located in the DTU control room. When the values approach the established fatigue endurance limit, an alarm is displayed. This helps the operator to plan, prepare and conduct the line replacement in a timely manner prior to failure thereby ensuring safe drilling operations. This lashing line integrity monitoring system has been working reliably for more than three years. Copyright 2014, Offshore Technology Conference.

Halkyard J.,John Halkyard and Inc. | Sheikh R.,BMT Scientific Marine Services Inc. | Marinho T.,Federal University of Rio de Janeiro | Shi S.,Houston Offshore Engineering | Ascari M.,Lockheed Martin
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2014

Ocean Thermal Energy Conversion (OTEC) was a subject of intense research in the late 1970s and early 1980s in response to a historical jump in oil prices from the 1973 oil embargo. The principal author for this paper first met Prof. Paulling as a participant in a National Research Council (NRC) Panel to review OTEC Technology around 1982. Prof. Pauling had authored a frequency domain program to analyze the coupled response of a platform and OTEC pipe. The author was involved in model tests to validate the program. The United States (U.S.) Department of Energy (DoE) and National Oceanic and Atmospheric Administration (NOAA) had sponsored this work, along with the development of other numerical methods. Shortly after the NRC completed its review, oil prices fell and interest in renewable energy, including OTEC, evaporated. Fast forward to the 2000s, the price of oil skyrocketed again, and OTEC research saw a rebirth. Lockheed Martin and others have been working on new OTEC designs over the course of the last several years. As was the case thirty-five years ago, the cold water pipe remains a key technical challenge. A commercial scale OTEC plant requires a pipe diameter of about 10- meter (m) and a length of 1,000m to pump about half the average discharge of the Colorado River from the deep ocean to the surface and through heat exchangers. Because of the large effective mass of the CWP and entrained water, the dynamic response of the OTEC CWP and the platform can only be considered as a coupled system. This conclusion is not new, but is worth repeating and doubly important to consider when the supporting platform is a semi-submersible as opposed to a large water plane ship shaped vessel. A new generation of software is available to analyze the cold water pipe-platform responses, including the important effect of the fluid flow inside the pipe and the local effects at the connection of the pipe to the platform. The DoE and Lockheed Martin recently sponsored a 1:50 scale wave basin model test of a commercial OTEC platform with an elastically scaled model of a 10m pipe. The purpose of the test was to validate the use of current software for the large CWP diameters in the designs of a pilot or commercial systems in the near future. This paper will briefly review past work on the OTEC coldwater pipe and present the current state of the art in numerical modeling and the results of the model tests recently completed. It will include recommendations for further experimental and numerical work to be prepared for the future design of OTEC systems. Copyright © 2014 by ASME.

Ledgard L.,BMT Group Ltd | Prislin I.,BMT Scientific Marine Services Inc. | Johnson T.L.,BMT Scientific Marine Services Inc.
Society of Petroleum Engineers - SPE Offshore Europe Conference and Exhibition, OE 2013 | Year: 2013

The design and operation of an FPSO in remote locations requires detailed information on the structural response of the vessel within the local environment offshore. Monitoring of critical components including the risers, hull and mooring lines simultaneously with the local environmental forcing of waves, wind and currents at the site location, provides a valuable insight into the performance and possible extension of the integrity life of the asset. Verification of the riser and vessel design is often theoretical and actual measured observation of the response of the critical components of an FPSO in the field is less frequent. As new technology is introduced, riser design becomes more sophisticated and extension of design life is required, it becomes increasingly important to monitor an assets performance. In hostile or remote locations where information on the environmental forcing is less known, monitoring becomes critical to assist with operational decisions, forensic investigation and the evaluation of design codes. This paper will provide a technical overview of an FPSO integrated marine monitoring system located in a hostile environment, typical of West of Shetland. The focus of this paper will be on the marine monitoring system; however an overview of the monitoring of subsea risers and moorings will be included for completeness. A discussion on the importance of monitoring the environment and the structural behaviour on a common time base for integrity management and forensic investigation of marine incidents will be presented. Copyright 2013, Society of Petroleum Engineers.

Prislin I.,BMT Scientific Marine Services Inc. | Jafarkhani R.,BMT Scientific Marine Services Inc. | Maroju S.,BMT Scientific Marine Services Inc.
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2015

Marine and structural integrity monitoring for offshore platforms is the cornerstone for managing operational risk and safety. Measuring platform responses and loads enables comparisons with design values thus ensuring that the risk does not exceed the designed limits. This paper discusses an advanced data management that is based on machine learning, a set of specialized computer programs that can learn and generalize the platform responses from measured data. The programs should produce sufficiently accurate predictions in previously unseen cases. Examples provided in the paper address capabilities for forecasting the marine and structural integrity parameters. © 2015 by ASME.

Sheikh R.,BMT Scientific Marine Services Inc. | Ewans K.,Royal Dutch Shell
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2015

Infragravity waves are long waves with periods of 30 to 300 seconds. They are most apparent in shallow-water and can have a large impact on the response of moored vessels, particularly large tankers such as LNG vessels, with long natural periods. A method for estimating infragravity wave design criteria for a shallow-water location is demonstrated. The method uses a combination of hindcast wave data and an idealised model for simulating infragravity waves. By way of example, a case study on the application of the Ideal Surf Beat (IDSB) model to simulate infragravity waves in the coastal waters of Barrow Island, Australia, and the subsequent estimation of extreme criteria quantifying the infragravity wave energy for a possible export berth location, is described. © 2015 by ASME.

Maroju S.,BMT Scientific Marine Services Inc. | Delaney K.,BMT Scientific Marine Services Inc. | Leon C.,BMT Scientific Marine Services Inc. | Prislin I.,BMT Scientific Marine Services Inc.
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2013

Integrated Marine Monitoring Systems (IMMS) are designed to help operators to reduce operational risk by providing information about the environment and the platform responses in real time. In spite of efforts to keep monitoring systems in working condition by following planned maintenance and upgrades, some sensors may fail intermittently or may generate spurious data. Quite often, intervention to repair or to replace a faulty sensor is either difficult, or even not feasible. This paper discusses various methods to estimate critical platform integrity parameters with satisfactory confidence in the cases when direct measurements are temporarily unavailable or questionable. Methods such as Artificial Neural Network and Extended Kalman Filter have been employed and specifically tuned to particular challenges. Estimated results for the missing data, such as platform position or riser loads, are reliable as they have been validated against historically good data. The merit of the paper is to present the methods that can increase reliability of the IMMS, enhance safety, reduce operational risk and decrease cost in maintaining expensive offshore systems. Copyright © 2013 by ASME.

Edwards R.Y.,BMT Scientific Marine Services Inc. | Le-Douaron S.,BMT Scientific Marine Services Inc. | Gallagher B.M.,BMT Scientific Marine Services Inc. | Prislin I.,BMT Scientific Marine Services Inc. | Duley D.,BMT Scientific Marine Services Inc.
Transactions - Society of Naval Architects and Marine Engineers | Year: 2011

Bending strain is the main contributor to fatigue damage in the touch-down zone (TDZ) of a Steel Catenary Riser (SCR). Measurement of the curvature in the SCR at the TDZ due to bending is essential to the validation of numerical models for SCR response and fatigue estimation. Long term SCR integrity monitoring systems may also require tools for the measurement of bending strain in the TDZ. In deep water, production SCRs typically have thick anti-corrosion and insulation layers that make the inference of the strain in the underlying pipe challenging. This paper describes the development of a strain measurement system and unique attachment scheme that can be literally built into the insulation and anti-corrosion layers on ultra deep water SCRs. Results of qualification tests will be presented that prove that the "insulation strain measurement system" produces a very accurate estimate of the strain in the underlying pipe steel. In addition, test results are presented that demonstrate that the attachment scheme does not threaten the integrity of the insulation and corrosion protection layers. Finally full scale bending strain measurement results will be presented from the TDZ of the Total AKPO Gas Export SCR in 1200 meters of water that illustrate the quality of the data, the excellent resolution and reasonableness of the results compared to numerical model predictions. © 2011, Offshore Technology Conference.

BMT Scientific Marine Services Inc. | Date: 2011-11-22

A system and method for the installation and removal of monitoring equipment is disclosed. In some embodiments, the monitoring equipment may be installed or removed using a remotely operated vehicle. In certain implementations, the monitoring system includes a sensor assembly connectable to a tubular member, an alignment tool for installing or removing the sensor assembly to and from the tubular member, and an alignment cage for facilitating access of the alignment tool to the sensor assembly. In some embodiments, the alignment tool may be aligned with the sensor assembly for installation or removal as a result of the alignment tool being inserted through the alignment cage.

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