【作者】 宋根才；

【导师】 闫相祯；

【作者基本信息】 中国石油大学 ， 油气工程力学， 2010， 博士

【摘要】 水平井技术以其特有的优势,在国内外范围内得到广泛的应用,并不断衍生出多种满足不同开采需求的复杂井况水平井类型,例如,中短曲率半径水平井、中短半径水平井和热采水平井等。这些技术的实施和推广极大地提高了采收率,显著地降低了生产成本,但这些技术的推广也为水平井完井套管柱的设计和套管损坏预防提出了新的要求和挑战,其中水平井完井套管损坏成为制约水平井技术在某些区域发展的关键影响因素之一。本文重点针对复杂井况水平井完井套管柱在下入、作业和热采过程中受力分析和强度校核等问题,通过理论分析、室内实验和数值模拟计算得到复杂井况水平井套管柱受力变形和损坏规律,并开发出相应的计算机软件,为复杂井况水平井完井套管柱设计和校核提供参考和依据,并提出具有针对性的预防水平井套管柱损坏措施和建议。第一,根据水平井完井套管柱在作业和生产过程中受力和变形特点,综合各种因素对水平井套管柱的影响,得到水平井套管柱应力分布和安全系数,对作业和生产过程中水平井套管柱的安全性进行评价,给出提高水平井套管柱安全系数的建议。第二,建立水平井套管柱在弯曲段的许可弯曲度,推导出相应的计算公式,并利用室内试验和三维有限元数值模拟计算进行验证,讨论各种不同因素对水平井弯曲段套管柱的许可弯曲度,为水平井完井管柱在弯曲段的设计提供参考。第三,分析了水平井套管柱在弯曲载荷作用下抗挤强度变化规律,研究结果认为弯曲应力是导致弯曲段套管柱损坏的主要因素,而弯曲作用产生套管柱截面不圆度对套管柱抗挤强度影响不显著,在实际计算过程中可以忽略,对已有计算弯曲载荷作用下套管柱抗挤强度计算公式进行了简化,方便现场使用和推广。第四,利用Visual Basic计算机语言编制复杂井况水平井完井作业管柱受力分析和强度校核软件,对现场使用的多口水平井完井套管柱进行了模拟计算,对其安全性进行了评价,为水平井套管柱设计和套管损坏预防提供数据支持。第五,建立了水平井完井预制孔套管抗挤塑性铰模型,推导了预制孔套管抗挤强度计算公式,讨论了孔径、孔密、相位角、初始椭圆度、径厚比等因素对预制孔套管力学性能的影响规律。第六,建立了热采过程中水平井完井套管柱受力模型,讨论了不同影响因素对套管柱损坏的影响,计算结果表明:水平井套管柱在热采过程中热胀变形无法释放使得套管柱发生强度和失稳破坏,可以通过安装补偿器和完井后对套管柱进行回拖,使得套管柱热应力得以释放,降低套管柱发生损坏的概率。第七,根据上述研究内容,针对不同因素引起的水平井套管损坏机理,进行套管保护综合措施研究,提出套管保护的综合措施和建议,延长水平井完井管柱使用寿命。更多还原

【Abstract】 Horizontal well technology is wide used in the oil and gas exploitation at home and abroad for its unique advantages. And many new types of horizontal wells are derived continuously to meet the needs of different type reservoirs exploitations, such as short-radius horizontal wells, multi-lateral horizontal wells and thermal recovery horizontal wells. The implementation and promotion of these new type horizontal wells greatly improve the oil and gas extraction rate, and significantly reduce the tons of crude oil production costs, but which also take higher requirements and challenges for the design and safety assessment of horizontal well completion casing strings. Some of the horizontal well casing completion technologies have become one of the key influencing factors restricting the use of horizontal well technology in certain areas.The main aims of this dissertation is to obtain the stress distributions and safety level of horizontal well casing completion strings during completion, operation and thermal recovery processes. Many existing researches, engineering experiences and theories are used during the study, which include modern mathematics, mechanics, computer and oil machinery theory.The stress and deformation calculating equations of horizontal well casing string under different work stations are deduced and verified by the results of experiments and numerical simulations. The computer software for horizontal well completion casing strings design and check is compiled basing on the calculating equations which can afford reference and data to take measures and recommendations preventing casings failures. The detailed studies of this dissertation can be made up by the following parts.(1) The stress distributions and the safety factors of horizontal well casing string are obtained according to the characteristics of loads and impact factors on the casing strings during completions and operations (such as fracturing). The safety of horizontal well casing strings is evaluated basing on the results. The recommendations of improving casing safety factor are also given.(2) The horizontal well casing strings collapse model is established and deduced the calculating equations, which locates at the built-up parts of horizontal well. The theoretical calculated results are tested by laboratory test and three-dimensional finite element simulation results. Various factors on the horizontal well casing strings collapse strength are discussed. These research results can serve as the references to the casing strings design at the built-up parts.(3) The collapse pressures of casing subjected to bending loads are studied. The calculating results show that the stress produced by bending loads is the main reseaon leading the casing failed. The ovality produced by bending loads has little effect on the collapse pressure of casing, which can be neglected in the actural engineering problems. According to the neglection, the formula of casing collapse strength subjected to bending loads has been simplified to facilitate on-site use and promotion.(4) Basing on the above findings, stress analysis and strength check software of horizontal well completion strings are compiled by VB computer language. Many horizontal wells completion casing strings were simulated by the software, their safeties were evaluated.(5) The plastic hinge model of perforated liner casing is built up to calculate the collapse pressure according to the strength and deformation behavior of perforated liner casing subjected to external pressure. The calculation equations of collapse pressure of perforated liner casing with initial ovalization are deduced by energy method. The influences of phrase angle, diameter of perforation, shot density, initial ovalization, diameter-thickness ratio and yield stress on the collapse pressure of perforated liner casing are studied.(6) The failure types of thermal recovery horizontal wells casing strings are classified as strength destruction and instability. The force model of completion casing during thermal recovery process is established the study the influences of different factors on the casing string damages. The recommendations and measures to prevent casing damage are proposed.(7) According to the contents of the above studies, different comprehensive measures to protect horizontal wells casing strings are carried out catering the different casing damage mechanisms, which are beneficial to extend the life of horizontal well casing strings.更多还原