Lateral Vibration Analysis of Oil Production Casing String in Deepwater Shallow Under Earthquake Excitations

Abstract The majority of deep-sea oil and gas exploration areas are located in seismic active zone, such as the South China Sea and Suez basin in Egypt. As casing string vibration caused by earthquake and low deep shallow soil cementation strength may result in the instability of deep water flow string, moreover, the pipe string failure may bring about economic loss and environmental damage. In this paper, lateral stability analysis of pipe in deep water shallow is taken into consideration for seismic analysis, and the string is considered as a Winkler model. First, it carries out stress analysis of flow string, and lateral stress includes wave load in wellhead, transverse moment imposed by bottom casing, ground resisting force and seismic force. Dynamic differential equation of string in deep water shallow is established on the basis of soil dynamics and pipe-string mechanics. Displacement attenuates and bending moment distribution of the string are calculated in three different seismic data, therefore the conclusion can be obtained as below: The string displacement amplitude increases as the intensity of earthquakes increases, and the biggest bending moment lies in the casing cross section, which is the point that may be easily damaged if the earthquake happens. In this paper, analysis of the transverse vibration of the shallow casing string wil help us better understand the casing string vibration in deepwater oil and gas exploitation and transportation so as to reduce the occurrence of the accident. Finally, some suggestions are given below, such as RMR \ MPD drilling technology, Open Hole Interval and structure of wellhead support device to enhance the stability of production string, ensure well integrity and reduce accident loss.