深水钻井作业管柱纵向振动载荷分析

Analysis of the Longitudinal Vibration Load of Deepwater Drilling String

深水钻井作业过程中,管柱在平台升沉振动的作用下产生纵向振动载荷,影响管柱的强度安全。以深水下表层套管作业管柱为例,建立了具有复杂结构的深水作业管柱纵向振动力学模型,并利用振动力学理论分析了管柱的纵向自由振动特性及纵向受迫振动载荷。分析结果表明,在平台升沉振动的作用下,作业管柱的纵向振动以第1阶振型为主;管柱顶端截面上的纵向振动载荷最大,是作业管柱上的危险截面;当钻井平台的升沉振动周期接近作业管柱的固有周期时,将产生极大的纵向振动载荷;当表层套管下入深度较大时,采用壁厚大的钻杆作为送入管柱能有效降低管柱纵向振动所产生的轴向应力。该项研究结果可为深水钻柱和送入管柱的设计提供依据。

In the process of subsea drilling, the string produces longitudinal vibration load due to the effect of platform heaving, which will affect the string strength safety. With lowering the subsea surface casing operation string as an example, the vertical vibration mechanical model of subsea operation string with a complex structure was established. The vibration mechanical theory was used to deal with the vertical free vibration property and vertical forced vibration load of the string. The analysis shows that due to the effect of platform heaving vibration, the vertical vibration of the operating string is mainly of the first-order vibration type. The maximum longitudinal vibration load appears on the cross-section of string top that is the dangerous section of the string. When the heaving vibration cycle of drilling platform is close to the natural cycle of the string, the remarkable longitudinal vibration load will arise. When the running depth of surface casing is considerable, adoption of drill pipe with large wall thickness as the running string can effectively reduce the axial stress caused by the vertical vibration of the string.