【作者】 张凤民；

【导师】 闫铁；

【作者基本信息】 大庆石油学院 ， 油气井工程， 2010， 博士

【摘要】 套管钻井技术就是用标准的油田套管边钻边封隔井眼,套管起着钻柱的作用,将机械动力和液压动力通过与最下部套管相连的钻具组合传给钻头,以实现钻进和钻井液循环,钻达设计井深后,起出下部钻具,进行固井。套管钻井技术把钻井和下套管合并成一个作业过程,钻头和底部钻具组合的起下用钢丝绳在套管内完成,不再需要常规的起下钻作业。套管钻井与常规钻井相比具有明显的优势,主要表现在能够缩短钻进时间、减小井下事故、改善井控状况、起下钻时泥浆能够连续循环、减小钻机尺寸、降低地面设备和后期作业费用、减少钻井过程对地层(储层)和地表的污染等方面,既保护了环境,又提高了单井产能,日益受到人们广泛的认识和普遍的应用。套管钻井过程中由于套管柱既是钻柱又是完井管柱,与常规钻井相比,套管柱的受力复杂程度、环空流体的流动状态及压力分布、套管柱的偏磨与损伤等明显不同。本文就是针对套管柱在井内受弯曲、扭转应力幅值大、环空内流体流动参数预测难于确定、接头螺纹受力大以及套管疲劳损坏失效等技术难点,利用弹性力学理论和有限元方法,分别建立了套管柱力学和数学分析模型、套管环空水力学模型和接头螺纹分析模型,得出一套适合于套管钻井过程中整体管柱分析的力学计算方法。应用该方法,能够优化钻井水力参数和优选接头螺纹,预防或减小套管柱损坏。通过全面系统的研究及应用,论文得出以下主要结论:(1)通过套管钻井动力学研究并结合套管钻井中旋转套管柱的力学行为分析,根据井斜方位的变化建立整体管柱的摩阻力分析力学模型,并进行了轴向拉压应力状态下的套管柱剩余强度的计算。在此基础上,通过对套管柱进行屈曲分析,确定了套管柱屈曲的临界载荷,优选了套管柱。(2)通过套管钻井水力学研究及应用流体力学的基本方程,建立环空压耗计算模型和轴向流动的动量方程,依此得出了钻井液流动规律。在此基础上,通过钻头射流的压力降、波动压力等参数的计算,准确地给出套管钻井中井筒环空钻井液的流态及流速的相互关系与压力分布,进而优选了套管钻井水力参数。(3)应用弹性力学理论,借鉴管柱螺纹研究的主要方法,通过对套管柱螺纹的受力和形变分析,建立了套管钻井套管柱连接螺纹的力学分析模型。依此计算得出了螺纹齿极限承载能力,校核了套管柱接头螺纹强度,并给出了补强套管螺纹的技术措施,为优选接头螺纹和特殊螺纹的设计提供理论依据。(4)考虑套管钻井中和钻后完井两个工艺过程,分别从力学和化学角度研究了套管柱疲劳与损伤破坏形式,得出了不同应力幅载下的疲劳强度及剩余强度,进而提出了预防套管损坏的技术措施。(5)应用本文所建立的理论模型,分别对扶余地区套管钻井的套管柱摩阻扭矩、钻头水力参数、螺纹连接强度、套管柱屈服和剩余强度等参数进行了计算,通过与现场实钻数据比较,水力参数误差在10%以内,能够满足施工要求。更多还原

【Abstract】 Casing drilling technology is that the standard casing is used to drill and pack off hole. The casing that plays the role of the drill string, will transmit mechanical and hydraulic power to drill bit through BHA which connects to the lower part of casing. It can remain drilling and circulating of drilling fluid. BHA will be hoisted and cementing will start after the wellhole is drilled to the design depth. The drilling and running casing are combined into an integral operation in casing drilling. The bit and BHA will be triped in casing with the cable and the trip operation in conventional drilling does not require any longer.Compared with conventional drilling, casing drilling has obvious advantages which mainly represent some aspects following. It can shorten the drilling time, reduce down hole accidents, improve the well-controlled conditions and cause drill fluid continuous to cycle while tripping. It also can decrease drilling rig size and the cost of later stage operating surface equipment and reduce the pollution on the layer(reservoir) and surface environment during the drilling. This not only protects the environment, but also increases the single well production, which causes people’s awareness and general application ever.Compared with conventional drilling process, casing string serve as drill string. This leads to obvious difference in straining complexity, flowing state and pressure distribution in annular space, eccentric wear and damage, and so on. Technological difficulties includes string bending in wellbore, lager twisting stress amplitude, definite prediction of annular fluid parameters, load on thread, fatigue and damage of casing. Focusing on these difficulties, the article builds up a set of mechanics model of whole casing string combining mechanics of elasticity with finite element method. The model can be used to analyze casing string mechanics, annular hydraulics and thread mechanics. Based on the above model, drilling hydraulics and thread can be optimized, and casing string failure can be prevented or decreased. Through overall and systematic research and application, the article gets main conclusions as follows:(1) Casing dynamics and rotating mechanics are jointly researched. String friction force of whole casing string is analyzed considering deviation and azimuth. Residual strength of casing string is calculated in axial tensile stress condition. Critical buckling load is defined by analyzing casing string buckling, and casing string is optimized.(2) The model of annular pressure loss calculation and momentum equation of axial flowing are built based on drilling hydraulics and application of basic hydromechanics equation. So flowing regularity of drill fluid is obtained. Based on calculating pressure drop of bit jet and fluctuating pressure, interrelationship between flowing pattern and velocity and pressure distribution in annular are presented accurately in casing and annular space, further hydraulics of casing drilling is optimized.(3) Elasticity mechanics theory is applied to research thread load. The model is built by analyzing strain and deformation of casing string thread. Thread teeth’s bearing limit is got, and the strength of sub thread in casing string is checked. Furthermore, technical measures of thread’s reinforcement is presented, which provides theoretical foundation for optimizing sub and special thread design.(4) Considering of the two processes in casing drilling and completion after drilling, the fatigue and damage types of the casing string are obtained respectively from the mechanics and chemical views. We obtain the fatigue strength and residual intensity in different stress loading and present further the technical measures of preventing casing damage.(5) By applying the theoretical models established in the article, many parameters are calculated respectively, which are friction and torque of casing string, bit hydraulics, thread strength of joint, buckling and residual intensity of casing string in the casing string in Fuyu region. By comparing with actual drilling data, the error of hydraulics parameters is less than 10% and meets the requirement of the construction work.更多还原