The quest for affordable energy continues to drive the need for new technology and push the limits of current practice. In the offshore arena of oil and gas exploration, massive drillships are used to penetrate reservoirs several thousand feet below the surface. The dynamic loading in the landing and casing string induced by an ocean environment is studied and a simplified model of heave in the string is developed in this thesis. An overview of the landing operations for intermediate casing strings and factors driving increasing lengths and weights of casing are presented. The available wave energy spectra for simulating the ocean wave environment and the ship’s response to such an environment (particularly in heave) are discussed. A literature review of previous models of dynamic loading in tubulars aboard offshore vessels is presented. The development and validation of a simplified model based on two real-world case studies are also presented. Contrary to prior assumptions, for models with 10 to 50 lumped masses, an increase in the number of masses significantly decreases the dynamic loads compared to using fewer masses. A comparison of the model results to the case studies suggests that vessel heave from the ocean environment induced only a portion of the dynamic loads observed. The dynamic loads observed in the case studies are on the order of only 1% of static string weight. Operations in extreme waves are also simulated, and the maximum dynamic loads predicted are less than 5% of static string weight.
|Advisor:||Vaughan, Joshua E.|
|Commitee:||Chambers, Terrence L., Emblom, William J.|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||MAI 56/05M(E), Masters Abstracts International|
|Subjects:||Ocean engineering, Mechanical engineering, Petroleum engineering|
|Keywords:||Casing, Deepwater, Heave, Landing string, Spider, Vibrations|
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