通过隔水管受力分析,提出了既能保证隔水管稳定性又能满足底部过提力要求的深水钻井隔水管顶张力计算方法,以南中国海某超深水井为例对其进行验证,并与两种常用计算方法进行了对比。基于管柱力学原理,分析了真实轴向力与有效轴向力对隔水管力学行为的影响,结果表明:真实轴向力决定隔水管底部对隔水管总成的拉力,有效轴向力决定隔水管稳定性。通过隔水管在内、外压作用下的受力分析,建立相应的力学模型,推导出新的顶张力计算方法,弥补了美国石油协会(API)算法和法国石油学院算法的不足。现场应用实例分析结果表明:采用该方法计算的顶张力设置值与现场实际作业时顶张力值基本一致,且计算结果优于API算法及法国石油学院算法的计算结果,可以用于指导隔水管设计及施工。图5表1参11
Through mechanical analysis, a calculation method which meets the requirements of both the riser stability and the bottom overpull margin was deduced. It was verified by an example of ultra deepwater well in South China Sea, and compared with two other common methods. Based on the related theories of pipe string mechanics, the effects of true axial force and effective axial force on the riser mechanical behavior were analyzed. The results show that, the bottom tensile force to Lower Marine Riser Package is determined by true axial force, and the riser's stability depends on effective axial force. Through the force analysis of riser which simultaneously bears the internal and external pressures, the correspondent mechanical model was established, and a new calculation method of top tension was derived, which remedies the deficiencies of algorithms proposed by American Petroleum Institute and Institute of French Petroleum. Field application shows that, the value of top tension calculated by this method is basically the same as the value set by field operation, and moreover, it is more accurate than the value obtained by the algorithms of American Petroleum Institute and Institute of French Petroleum. This method can be used to guide the design and operation of conductor.