【作者】 张永贵；

【导师】 李子丰；

【作者基本信息】 燕山大学 ， 机械设计及理论， 2008， 博士

【摘要】 稠油开采通常采用热采技术。稠油热采分为蒸汽驱、蒸汽吞吐和火烧油层等方法,其中在蒸汽驱和蒸汽吞吐采油技术中存在的油井套管损坏问题一直是严重影响稠油产量和企业经济效益的大问题。理论上研究稠油热采井套管损坏问题有各种不同的出发点和相应的方法,本文以稠油热采井的实际条件为基础,重点研究了在热采井复杂受力条件下,如何通过降低套管应力来防止套管损坏或降低套管损坏率的问题。论文主要研究内容可概括为如下几个部分:(1)在确定了基本研究内容和研究方向的基础上,进行了井筒流体参数计算方法研究,目的是获得井筒内流体参数及其变化规律,并进一步获得套管强度研究所必需的套管温度、井筒压力及水泥环温度等数据。计算过程中将湿蒸汽两相流理论与工程热物理中的流体热物性计算方法有机结合,创造性地解决了井筒流体参数及井筒温度场的计算问题,实现了流体计算过程的连续性,既提高了计算精度,又提高了计算速度。(2)根据热采井的工作条件,建立了稠油热采井套管的力学模型,研究了模型中各种内、外力尤其是热应力和外挤压力的计算方法。在套管力学模型中充分考虑了地层与套管的相互作用关系,建立了套管与地层相互作用关系模型。分别计算了蠕变地层、理想刚性地层及弹性地层条件下的套管外挤力。通过计算对比,获得了导致套管柱危险井段损坏各种因素的影响情况信息。模型中关于地层与套管之间作用关系的研究结果,完善了目前理论界对该问题研究的不足。通过系统的研究、计算,明确了造成热采井套管损坏的最重要原因是热应力这一重要结论,指出热采井套管损坏问题研究的重点应该是如何减小热应力。对于普通油井的套管损坏问题,地层的蠕变性则是最重要的原因。由于地层的蠕变特性是无法改变的,因此,应从生产工艺、套管材质及套管质量方面研究普通油井套管损坏的对策。另外,对套管轴向应力的研究表明,预应力固井对热采井套管应力状况具有一定的改善效果,但对于不同的井段,施加预应力的大小及方向需要区别对待。(3)为验证本文的计算方法和研究结论,在辽河油田选择了试验井并进行了注蒸汽试验。试验数据处理结果证明,本文的计算方法是正确的,计算结果与试验情况基本相符,同时也符合人们对热采井井筒参数变化规律的一般认识。(4)利用本文的计算方法,对辽河油田正在试验中的真空隔热套管从隔热性能和强度两方面进行了评价。评价结论认为,真空隔热套管井筒的隔热性能要好于目前的井筒;在强度方面,真空隔热套管的内管强度余量偏小,尤其是在注入蒸汽压力较高的情况下,内管破坏的可能性很大,而外管的强度余量较大。由于真空隔热套管具有优良的隔热性能和可以简化蒸汽吞吐采油工艺的特点,只要适当提高内管强度,真空隔热套管技术就会具有广阔的发展前景。本文关于隔热套管井筒的评价,在国内外均属首次进行。必须指出的是,本文是以一口深1000m的热采井为研究对象的,随着井深的增大,作用于套管的各种力的相对大小将发生变化。因此本文的研究结论具有一定的针对性。更多还原

【Abstract】 Thermal recovery method, which can be subdivided into steam flooding, steam stimulation, in-situ combustion and so on, is commonly adopted for heavy oil production. When adopting steam flooding or steam stimulation method, the issue of oil well casing damage has been a serious impact on many enterprises’ heavy oil production and economic efficiency. Based on actual conditions of heavy oil thermal recovery wells, it is researched in this paper how to reduce well casing’s stress to prevent or lighten its damage. Main research work is summarized as follows:(1)The calculation methods of well casing fluid parameters are researched to obtain fluid parameters and their variation laws, and further well casing temperature, well casing pressure and cement hoop temperature are obtained to study well casing’s strength. Fluid thermo-physical properties in engineering thermal physics and the theory of wet steam two-phase flow are effectively integrated to creatively solve the problem of continuous calculation of fluid parameters. The accuracy and speed of calculation are both increased.(2)According to working conditions of the thermal recovery wells, the mechanical model of heavy oil thermal recovery well casing is established. Calculation methods of various internal forces and external forces are researched, especially thermal stress and external squeeze pressure. The interaction between the casing and formation is taken full account of in the mechanical model. External squeezing forces of the casing were separately calculated under the conditions of creep formation, ideal rigid formation and flexibility formation. The information of various influence factors resulting in the dangerous well casing sections’ damage are obtained by contrast. The research of interaction between the casing and formation are perfected by this study. It is concluded that thermal stress is the most important reason causing thermal recovery well casing’s damage, and so how to reduce the thermal stress should be the emphasis of thermal recovery well casing damage’s research. The creep of formation should be the most important reason resulting in well casing’s damage for ordinary oil wells. The creep properties of the formation can not be changed. Therefore, the production process, the casing material and the quality of the casing should be researched to prevent ordinary oil well casing’s damage. In addition, the improvement of thermal recovery well casing’s stress condition resulting from pre-stress is proved by the research on well casing’s axial stress. But the magnitude and direction of pre-stress should be distinguished because of different oil wells.(3)A steam flooding experiment is carried out in a test well casing in Liaohe oil field to verify calculation methods and conclusions proposed in this paper. Calculation methods and conclusions proposed this paper are proved to be correct.(4)The vacuum-insulated casing with excellent insulation properties can simplify the steam stimulation process, so as long as the appropriate increase in the intensity of vacuum insulated casing technology will have broad prospects for development. Based on calculation methods proposed in this paper, the insulation performance and strength of the testing vacuum insulated casing in Liaohe oil field are evaluated. The insulation performance of vacuum insulated casing is better than the current well casing. The strength residue of the internal tube of vacuum insulated casing is small, especially when high-pressure steam is injected, but the strength residue of the external tube is relatively great. The vacuum-insulated casing with excellent insulation properties can simplify the steam stimulation process. So as long as the internal tube’s strength is improved, vacuum insulated casing will have broad prospects for development. The evaluation of insulation casing is firstly carried out in the world.It should be pointed out that the research conclusion proposed in this paper is based on the study of a thermal recovery well with a depth of 1000 meters and has its applicability. The magnitude of various forces acting on well casing should vary with the increase of well’s depth.更多还原