基于钻井系统动力学的深海钻井升沉补偿系统机理研究

The floating drilling platform is the core equipment in developing the petroleum and gas resource in deep sea areas. As a result of coupling effects of the ocean wave and drill string vibration, the bit fluctuates during the deepwater drilling period directly impacting penetrating efficiency of downhole bit. Heave compensator is exactly the key equipment to ensure the drilling performance of floating drilling platform. The research on the regularity of platform vibration caused by ocean wave, ocean wind, drilling equipments and so on will be carried out in the project based on the floating multi-body system model including marine riser, drilling platform and drilling equipments. By building the drilling system dynamic model in deepwater drilling environment, the features of deepwater drilling system dynamics based on deepwater drilling environment will be studied to find the vibration regularity of deepwater drilling string. Through the study on working mechanism of heave compensator based on coupling effects of drilling platform and deepwater drilling system dynamics, the movement rule of downhole bit under the influence of deepwater drilling platform fluctuation and drill string vibration will be found so as to establish design criterion for heave compensation system used in deepwater drilling. The model will be solved by modern mathematics and simulation study on working performance of heave compensation system in different working conditions will be completed by developing simulation software. Theoretical basis for further theoretical study on deepwater drilling and development of heave compensators which satisfy deepwater drilling requirements of our country will be provided.

深海油气资源开发的核心装备是浮式钻井平台，由于海浪和数千米钻柱振动的耦合作用导致深海钻井过程中钻头上下波动，直接影响井下钻头的破岩效率。升沉补偿系统是确保浮式钻井平台正常钻井的关键装备。本项目通过建立包括隔水管、钻井平台和钻井装备在内的一个浮式多体系统模型，开展水深、风浪、洋流和钻井装备等导致浮式钻井平台振动的规律研究；通过建立基于深海钻井环境下钻井系统动力学模型，研究基于海洋环境下深海钻井系统动力学特性，找到引起深海钻井钻柱振动规律；通过开展基于钻井平台和深海钻井系统动力学耦合作用下升沉补偿系统工作机理研究，找到深海钻井平台波动和钻柱振动导致井下钻头运动变化规律，由此建立深海钻井升沉补偿系统设计准则；采用现代数学方法实现对模型的求解，通过开发仿真软件，实现不同工况下深海钻井升沉补偿系统工作性能仿真研究；为进一步开展深海钻井相关理论研究和研制满足我国深海钻井要求的升沉补偿装置提供理论依据。

升沉补偿系统是确保浮式钻井平台正常钻井的关键装备。项目开展以来分析了浮式钻井平台升沉运动对钻井作业的影响，建立了钻井平台升沉运动模型；建立了考虑平台运动与系统真实配置的隔水管动力模型，采用有限单元法对模型进行求解；建立了升沉补偿装置和钻柱系统的振动动力学模型，深水钻井钻机-钻柱-钻头井底岩石系统动力学模型，采用有限差分法对模型进行求解；基于相似理论，建立了浮式钻井平台-隔水管-钻柱系统力学行为实验装置，并开展了均匀流、剪切流作用下钻机-隔水管-钻柱相互耦合作用实验研究；提出了一种新型机械驱动式天车升沉补偿装置的方案；对新型天车升沉补偿装置具体结构参数进行了计算，设计出一种新型天车升沉补偿装置；建立了天车升沉补偿装置方案设计评价分析方法，基于天车升沉补偿装置方案设计分析要素，提出了天车升沉补偿装置方案设计系统分析步骤。通过项目研究，得到了以下几点认识和结论：浮式钻井平台在升沉运动过程中，附加质量和辐射阻尼随平台运动圆频率的变化而产生了较大幅值的波动，钻井平台的辐射效应在不同自由度运动条件下的都会随平台运动圆频率在一定范围内产生较大波动；系统配置对隔水管动力学行为有明显影响；隔水管变形、偏角以及弯矩随张紧力、表面海流流速、平台偏移量、波高、波速的增大而增大；近钻头处扭转振动相较于海底防喷器处规律性更差，同时海底防喷器处的钻柱扭转角速度波动更大；海水深度、钻具组合、钻压和扭矩对系统动力学有明显影响；钻柱对隔水管涡激振动振幅有一定抑制作用，但钻柱转速对隔水管动力特性无明显影响；液压缸中产生的摩擦力对井底钻压波动的影响明显，且曲线随时间的变化而快速波动；经过系统的仿真，新型设计的机械驱动式天车升沉补偿装置对补偿效率约提高了30%。