The Research Of Bearing Capacity Of Conductor For Deepwater Drilling

As drilling operations move to deepwater, subsea wellhead bears complex stressbecause it joins the marine riser and casings. The stability of subsea wellhead becomesincreasingly concerned. The vertical and lateral bearing ability of conductor and casingwill directly affect wellhead stability. If the conductor is less size or less setting depth,wellhead instability, well fallen and other drilling accidents will happen. On the contrary,it will cause unnecessary waste. Therefore, the researches on bearing capacity and settingdepth of conductor are particularly important.Based on the ABAQUS finite element analysis software, this paper analyzes thelateral stability of conductor. Firstly, a model for the conductor lateral loads has been builtusing ABAQUS simulation software. In the model, the conductor is seen as aequal-strength beam inserted into soil. Applying the p-y curve method to describe thenonlinear subgrade reaction between conductor and soil, and Using the nonlinear springunit of ABAQUS software simulates nonlinear soil resistance which the conductor isbearing. An example and comparing with professional softwares(FLPIER、COM624P andGPILE) prove the reliability of this model. At last, diameter, thickness, setting depth andwellhead load that influence the lateral loading capacity are analyzed.According to the process of running conductor, this paper analyzes the mostdangerous conditions in the process, in which the conductor is bearing the largest verticalload. Based on the pile foundation theory and the knowledge related soil mechanics, thisthesis analyses the loading state of conductor and establishes vertical loads models ofconductor and calculation method.Combining with time effect of pile bearing capacity, this paper draws the mostreasonable setting depth of conductor. By comparing several prediction ways of the timeeffect of pile bearing capacity, the author chooses a suitable method for our deepgeological condition, and combining with the largest conductor vertical load ,the authordesigning the most reasonable setting depth of conductor. By analysising an example, theauthor stadys the impacts on conductor vertical bearing capacity has also been considered,such as diameter, thickness, recovery time and coefficient of bearing capacity. On the basis of theory research above, the design software of conductor setting depthis developed by Visual Basic 6.0, which are meaningful in designing the setting depth ofthe conductor of deep water drilling.