半主动式钻柱升沉补偿系统补偿机理分析

运用达朗伯原理,结合钻柱的运动规律,分别建立了并联和串联2种形式的半主动式钻柱升沉补偿装置力学模型,分析比较这2种半主动式升沉补偿装置的补偿机理。结果表明,在半主动式升沉补偿系统中,被动补偿部分所起的作用是支撑钻柱的大部分质量,主动补偿部分只是用来补偿各种力的变化量;由于并联式结构比串联式结构的执行原件多,所以其液压系统相对复杂,但当船体升沉位移较大和深海钻进所需的补偿负载较大时,并联式结构又优于串联式结构;在正常钻进工况下,当控制目标为控制井底钻压不变时,并联式钻柱升沉补偿系统只能通过控制补偿系统的输出力恒定来达到控制目标,而串联式结构则可以通过控制补偿系统的输出压力或输出力恒定来达到控制目标。

Analysis of the Compensating Mechanism of Semi-active Drill String Heaving Compensation System

Applying the d’Alembert principle and referring to the movement law of drill string,the parallel and serial dynamic models of semi-active drill string heaving compensation device were established.The compensating mechanism of the parallel and serial semi-active drill string heaving compensation systems were analyzed and compared.The findings show that the function of the passive compensation part in the system is to support most of the mass of drill string and that of the active compensation part is to compensate the variation of various forces.The hydraulic system of the parallel structure is quite complex due to the fact that there are more executing components in parallel structure than in serial structure.However,when the generated displacement of the hull is remarkable and the compensation load required by subsea drilling is relatively large,parallel structure is better than serial structure.The parallel drill string heaving compensation can only reach the control goal through the output force of the control compensation system when the control goal is to keep downhole drilling pressure unchanged in normal drilling conditions.But the serial structure can reach the control goal through controlling the output pressure or keeping constant output force of the compensation system.