大庆油田萨中开发区标准层地层滑移与套管剪切损坏机理研究

发布时间：2019-04-24 19:32

【摘要】：在油田开发过程中,套管损坏问题始终存在,并且已经成为影响油田生产的重点和难点问题,特别是油田注水开发引起的套管损坏问题,一直都是国内外学者研究的重点,至今仍末得到很好的解决。大庆油田萨中开发区标准层套管损坏与以往注水开发油田套管损坏特点存在较大差别,主要表现在该区域套管损坏以剪切变形和错断为主,套管损坏发生的区域集中、时间集中,且发生套损的层位一致。本文针对大庆油田萨中开发区标准层套管损坏问题,开展相应实验研究和有限元数值模拟计算,期望通过本文研究揭示标准层套管损坏的力学机理,并为油田开发过程的套损防控提供理论方法。论文首先对萨中开发区实验区块的套管损坏形态、层位等资料进行统计,确定套管损坏的原因和发生套管损坏的层位,在此基础上对实验区的地质特征和套损层位地层岩性特征进行分析,明确岩石力学实验和数值模拟研究的建模对象。其次,开展实验区标准层部位页岩和泥岩的岩石力学参数测试,通过实验测定不同取心方向页岩和泥岩的抗拉和抗剪切强度、单轴和三轴抗压强度以及弹性模量和泊松比等重要力学参数,实验表明不同取心方向页岩和泥岩力学参数差异明显,存在明显各向异性特征,页岩和泥岩沿层理容易发生张拉与剪切破坏,且页岩层理间内聚力明显低于泥岩,更容易沿层理方向产生破坏,形成水平裂缝。根据标准层地层岩性特征建立相应有限元模型,通过有限元数值模拟研究得出：地层上抬会在标准层部位产生应力集中,标准层层理发育抗剪切强度低,最易成为应力释放的层位而产生地层滑移,导致套管剪切破坏发生,并且通过数值模拟分析了油层上部地层厚度、标准层相对位置等参数对地层滑移量的影响,得出地层滑移量与各影响参数间的函数关系,建立了层间滑移量最大值计算模型。采用实验区的实际地层数据,结合岩石力学参数实验结果,基于流固耦合理论,建立了标准层地层滑移的有限元数值模型,通过数值模拟计算了研究区块2009～2010年间注水开发过程的地层纵向变形和标准层相对滑移量等数据,结果表明：地层高压区位置纵向位移量大,而低压区标准层层间滑移量大,模拟计算判别的套管损坏情况与实际情况符合率达到86.76%。最后,应用建立的实验区三维有限元模型,计算了不同区域间压差所产生的标准层地层滑移量分布变化,并提出采用反距离加权计算区域地层压力的方法来计算引起标准层套损的区域间压差临界值,研究表明：区域间压差越小,相应的标准层地层滑移量越小,实验区块安全的区域间压差上限为0.67MPa。
[Abstract]:In the process of oilfield development, casing damage has always existed, and has become a key and difficult problem affecting oilfield production, especially casing damage caused by oilfield waterflooding has always been the focus of research by domestic and foreign scholars. It is still a good solution to this day. Casing damage in the standard layer of Sazhong Development Zone of Daqing Oilfield is quite different from that in the past, which is mainly manifested in the fact that the casing damage in this area is mainly caused by shear deformation and dislocation, and the casing damage is concentrated in the area where casing damage occurs. Time concentration, and the occurrence of casing damage of the layer consistent. Aiming at the problem of casing damage in standard layer of Sazhong Development Zone of Daqing Oilfield, the corresponding experimental study and finite element numerical simulation are carried out in this paper. It is expected that the mechanical mechanism of casing damage in standard layer can be revealed through this study. It also provides a theoretical method for casing damage prevention and control in oilfield development process. First of all, the paper makes statistics on the casing damage form and horizon of the experimental block in Sazhong Development Zone to determine the cause of casing damage and the horizon where casing damage occurred. On this basis, the geological characteristics and lithologic characteristics of casing-damaged strata in the experimental area are analyzed, and the modeling objects of rock mechanics experiment and numerical simulation are defined. Secondly, the rock mechanical parameters of shale and mudstone in the standard layer of the experimental area are tested, and the tensile and shear strength of shale and mudstone in different coring directions are measured by experiments. Some important mechanical parameters, such as uniaxial and triaxial compressive strength, elastic modulus and Poisson's ratio, are tested. The experimental results show that the mechanical parameters of shale and mudstone in different coring directions are obviously different and have obvious anisotropic characteristics. Along the bedding, shale and mudstone are prone to tensile and shear failure, and the cohesion between shale formations is obviously lower than that of mudstone, so it is easier to destroy along the bedding direction and form horizontal fractures. According to the lithologic characteristics of the standard layer, the corresponding finite element model is established. Through the finite element numerical simulation, it is concluded that the stress concentration will occur in the part of the standard layer, and the shear strength of the standard layer will be low, and the shear strength of the standard layer will be low. The formation slip is the most easily released layer, which leads to casing shear failure. Through numerical simulation, the influence of formation thickness and relative position of the standard layer on the formation slip amount is analyzed, and the influence of the parameters such as the thickness of the upper layer and the relative position of the standard layer on the formation slip is analyzed. The function relation between the stratum slip and the influence parameters is obtained, and the calculation model of the maximum inter-layer slip displacement is established. Based on the fluid-solid coupling theory, the finite element numerical model of strata slip in the standard layer is established based on the actual formation data in the experimental area and the experimental results of rock mechanics parameters. The data of formation longitudinal deformation and relative slip of standard layer in the process of waterflooding development in 2009 / 2010 are calculated by numerical simulation. The results show that the vertical displacement of formation high pressure area is large, while the slip between standard layers of low pressure area is large, the results show that the vertical displacement of formation high pressure area is larger than that of low pressure zone. The coincidence rate between the casing damage and the actual situation is 86.76%. Finally, the three-dimensional finite element model of the experimental area is used to calculate the variation of the slip amount of the standard layer caused by the pressure difference between different regions. An inverse distance weighted calculation method of regional formation pressure is proposed to calculate the critical value of inter-regional pressure difference resulting in casing damage of the standard layer. The results show that the smaller the inter-regional pressure difference, the smaller the slip amount of the corresponding standard layer formation. The upper limit of the safe inter-zone pressure difference for the experimental block is 0.67MPa.
【学位授予单位】：东北石油大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE931.2

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