【作者】 阳鑫军；

【导师】 李子丰；

【作者基本信息】 燕山大学 ， 机械设计及理论， 2011， 博士

【摘要】 稠油是油气资源的重要组成部分,我国稠油资源约占总资源的20%-25%,已探明的储量超过13亿吨。开采稠油有蒸汽驱、蒸汽吞吐和火烧油层等热力法,我国一般以蒸汽吞吐方法为主。热采井在注蒸汽几轮次后常出现套管损坏现象,给油田生产造成巨大的经济损失。本文在对国内外套管损坏现状和预防措施深入分析的基础上,对防止热采井套管损坏的预膨胀固井技术进行了全面研究。首先阐述了稠油开采方式和注蒸汽热采井的井身结构特点,分析了套管受力,并结合热采井套管损坏部位和损坏形式等统计数据,得出了注蒸汽热采井套管损坏的主要原因以及受热应力的主要部位,并对研究模型进行了相应简化。依据在初始状态时就已受到地应力作用的地层上钻井的套管—地层相互作用模型,建立了刚性地层、弹性地层和蠕变地层条件下套管所受外挤力的计算模型。对于固井过程中处于自由膨胀状态下的套管,运用厚壁圆筒平面应力问题理论建立了套管的应力计算力学模型。对于生产过程中受热变形受到固结水泥环限制的套管,运用厚壁圆筒平面应变问题理论建立了套管的应力计算力学模型,以及弹性水泥环和地层的位移计算模型,并根据套管—水泥环—地层围岩接触处的位移协调方程,阐述了不同地层条件下套管外挤力的计算方法。由力学模型计算出了不同注气温度下生产过程中套管的有效应力强度,利用Mises屈服准则分析了热采井套管损坏的力学机理。在前述工作的基础上,完善了预膨胀固井理论模型。建立了采用预膨胀固井技术时以及水泥浆凝固后生产过程中套管应力计算力学模型,由力学模型分析了预膨胀固井技术保护套管的力学机理。通过实际油井数据计算了油井分别采用常规固井、不同预热温度的半预热固井和不同预压压力的预压固井时套管在整个生产过程中的应力和状态,由计算结果分析了防止套管热破坏的比较合理的预热温度和预压压力范围。并根据力学模型设计了不同井深、不同注汽温度下的N-80套管的预压压力值。最后根据稠油热采实际生产情况、简化的研究模型以及预膨胀固井理论要求,设计了室内模拟预膨胀固井实验平台,并进行了水泥浆性能测试、实验用铝管性能测试以及相应的模拟常规固井、半预热固井、预压固井和注蒸汽/生产过程等实验。对比了采用不同固井方式时铝管在实验前后的内径变化情况,分析了预膨胀固井技术对套管变形的影响。更多还原

【Abstract】 Heavy oil is an important constituent of hydrocarbon resources. In China, it takes up 20% to 25% of the total with proven reserves of over 1.3 billion tons. Technologies of heavy oil recovery include steam drive, steam stimulation, in-situ combustion, etc., and steam stimulation is adopted the mostly in China. However, after several rounds of steam injection, casing failure often occurs, which causes huge economic losses. Based on analysis of current situations of casing failure and preventive measures at home and abroad, this paper carries out a comprehensive study of pre-expansion cementing technology in preventing casing failure in thermal recovery wells.The paper first introduces methods of heavy oil recovery and the wellbore configuration of steam injection thermal recovery wells. Based on analysis of the stress and damage of casing, it is found that the main cause of casing failure of steam injection thermal recovery wells is continuous thermal stress on the section at oil reservoir. Therefore, the research model of present study is simplified as a combination of casing at oil reservoir section, cement sheath and the formation.By analyzing the interaction model of the casing and the formation with strata stress in an initial state, respective formula for the external pressure on casing is derived under conditions of rigid formation, elastic formation and creep formation. Based on the thick cylinder plane stress theory, a mechanical model of stress calculation is established for casing in the state of free expansion during the cementing process. By adopting the thick cylinder plane strain theory, the study specifically establishes a mechanical model for stress calculation of casing during the production process of steam injection thermal recovery wells. According to the compatibility equation of displacement between casing, cement sheath and the formation, calculating methods are elaborated for the external pressure on the casing in different formations. The study also figures out the effective stress intensity of casing during the production process and analyzes the mechanical mechanism of casing failure in thermal recovery wells by Mises yield criterion.Based on aforementioned work, the study improves the theoretical model of pre-expansion cementing. It also establishes mechanical models of stress calculation on the casing at different stages and under different formation conditions with pre-expansion cementing technology. With these models the mechanical mechanism of casing protection is further analyzed. Apart from theoretical analysis, by adopting data from actual oil wells, the study also calculates respectively the stress and state of casing during the whole production process with conventional cementing, half pre-heating cementing with different temperatures, and pre-pressurization cementing with different stress. The results help in deriving appropriate ranges of pre-heating temperature and pre-pressurization stress for prevention of casing failure.Finally, to verify the rationality of the theory, an indoor simulation of pre-expansion cementing experimental platform is designed according to the simplified research model and requirements of pre-expansion cementing theory. Performance tests of the cement slurry and the experimental Al pipe are carried out as well as corresponsive simulated production experiments including conventional cementing, half pre-heating cementing, pre-pressurization cementing and steam injection.更多还原