DynaMAC: Molikpaq Ice Loading Experience

• Main Authors: Hardy, M., Jefferies, M., Rogers, B., Wright, B.
• Format: Report
• Language: unknown
• Published: National Research Council Canada 1996
• Subjects: Canada; Beaufort Sea
• Online Access: https://dx.doi.org/10.4224/12328378; https://nrc-publications.canada.ca/eng/view/object/?id=9475864c-6e0d-4f70-9fc8-5747787f915d

This report to the National Energy Board presents a compendium of ice loading events experienced by the Gulf Canada Resources Ltd. offshore platform "Molikpaq". To date, the primary interest in the Molikpaq has focused on a single event (the 0800 hr ice loading event on April 12th, 1986 at Amauligak I-65) which has perhaps led to some unbalanced views about the response of the Molikpaq during its four deployments in the Canadian Beaufort Sea. The intent of this report is to make the ice mechanics community more aware of the range of ice-structure interactions and ice load levels that the Molikpaq has experienced during the four winter deployments. Four winters of operation at four different locations have produced an enormous amount of data, far more than can be realistically used within a research context. However, much of the ice interaction data are similar. An objective of the work carried out for this report was to review the available information and filter out about 30 days with events which capture the key aspects of Molikpaq icestructure interaction and for which the available information is suitable for further research use. Icestructure interaction events where ice failed directly against the caisson are of most interest and are available from the first two deployments at Tarsiut P-45 in 1984/85 and at Amauligak I-65 in 1985/86. At these locations the Molikpaq was deployed at a setdown draft of 19.5 metres, which resulted in no permanent accumulation of rubble ice around the caisson. A total of 10 operating days at Tarsiut P-45 and 19 operating days at Amauligak I-65 have been selected that contain representative periods with both ice documentation and Molikpaq instrumentation response data. A further objective of this study is to summarize how the reported loads were derived from the sensor data, and to address concerns about potential structural resonance and overall load estimate accuracy. The Molikpaq was deployed for hydrocarbon exploration and the acquisition of the ice structure interaction data was peripheral to its principal activity which was oil drilling. One consequence of this is that the extent of the sensor arrays and the completeness of the ice documentation was pragmatic, and perhaps less complete than ice researchers might wish. This in turn has led to some uncertainty over the magnitude of reported ice loads on the Molikpaq, which has been exacerbated by the divergent views on ice loads within the ice community. Therefore, this report presents an overview of how ice loads have been calculated and importantly identifies the traceability of these reported loads to reference calibrations. To provide researchers with confidence in their understanding of the data, a computer program running under the Microsoft Windows environment was developed to read and process the information obtained from the Molikpaq data acquisition system. The program, called DynaMAC, operates on the Molikpaq data sets which have been transferred from the original HP format to the industry-standard MS-DOS form and duplicates much of the functionality of the software developed by Gulf Canada Resources Ltd. Default calibration factors in DynaMAC correspond to values used for the Gulf Canada Resources Ltd. sponsored Dynamics Project and as such, this software provides a starting point for researchers to verify data records by reproducing the ice load plots previously reported. The program DynaMAC was further developed to provide a means of accessing a database that contains the ice documentation, and site photography from the Amauligak I-65 ice events. This information, together with data on sensor status and location, availability of video records, and the response data has been stored on a CD-ROM, as illustrated below.