Simulation Experiment and Mechanism Research on the Change of Lateral Friction Against Surface Conductor in Deepwater Drilling
| Autor: | Li He, Zhu Yi, Wei Meng, Jin Yang, Hu Nanding, Yihui Zhao, Wang Xiao, He Deng, Tong Gang |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Surface (mathematics)
Engineering Petroleum engineering business.industry 05 social sciences 010502 geochemistry & geophysics 01 natural sciences Conductor Mechanism (engineering) 0502 economics and business Geotechnical engineering business 050203 business & management Deepwater drilling 0105 earth and related environmental sciences |
| Zdroj: | Day 3 Wed, May 04, 2016. |
| DOI: | 10.4043/27085-ms |
| Popis: | Lateral friction against surface conductor plays an important role in the stability of subsea wellhead. It changes during jetting process and increases with soaking time. But the change rule and mechanism remain unclear. Therefore, the purpose of this paper is to explore the change mechanism of lateral friction during and after conductor jetting process by field experiment and numerical simulation. Firstly, a field experiment was conducted to simulate actual surface conductor jetting process. The time- dependent change rule of radial pressure, pore water pressure and effective skeleton pressure were obtained. Then, the stress states of soil bodies during this process were analyzed. Based on experiment and analysis results, the primary reason that causes the change of lateral friction was found. After that, to explore the specific change features of bearing capacity of seabed soil for surface conductor, another field experiment was conducted. Finally, finite element method was adopted to simulate the conductor jetting process and to verify the research conclusions. The field simulation experiment showed that the sensor at the base of surface conductor suffers conspicuous higher value of radial pressure than other sensors above. Meanwhile, the effective pressure of each layer has a tendency of declining as time increasing and then gradually adds after reaching a certain value. These regularities matches the change rule of radial pressure on piles during driving process. Based on the stress analysis, it is certain that the soil compaction effect does exist in conductor jetting process, caused by which, the formation and dissipation of pore water pressure during jetting process would be highly related to the change of lateral resistance against surface conductor. After jetting into position, soil lateral friction would increase with time non-linearly. The change rate would gradually rise at the first 10 hours. After 72 hours, the added values of friction are small and the change rate turns to flat. According to the numerical modeling results, under the action of jetting force, on one hand, soil bodies that are closed to bit are cut into grains and flow out from wellbore with drilling fluid; on the other, soil bodies that are farther from bit would be squeezed down and then pushed around. Previous studies mainly considered the soaking time and bearing capacity of surface conductor, focused on specific values. This research designed a system to simulate surface conductor jetting process to explore the change mechanism of lateral friction against surface conductor by combining the method of numerical modeling and field experiment. |
| Databáze: | OpenAIRE |
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