硬脆性页岩井壁稳定性水化作用影响研究

发布时间：2018-02-27 09:35

本文关键词： 硬脆性页岩水化作用微观结构坍塌压力　出处：《西南石油大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,随着我国对石油天然气资源需求量的不断增大,各大石油公司也加大了页岩气勘探开发的力度,然而硬脆性页岩地层井壁稳定性问题一直是制约深层油气资源安全高效开发的技术瓶颈,特别是水化作用对硬脆性页岩井壁稳定的影响。因此,为了揭示硬脆性页岩地层井壁失稳的机理,选择某研究工区硬脆性页岩为研究对象开展室内试验研究,包括矿物组成、比表面积、润湿性、阳离子交换容量、微观结构及三轴压缩试验,研究了浸泡钻井液对研究工区硬脆性页岩强度特性的影响。基于以上试验得出硬脆性页岩理化特性、力学特征,分析了由于页岩本身性质导致页岩地层井壁失稳的原因及水化作用对硬脆性页岩井壁失稳的影响。并基于页岩力学特性以及井周应力建立了研究工区目直井的坍塌压力计算模型,分析了钻井液浸泡时间对坍塌压力的影响。研究结果表明： (1)研究工区目的层硬脆性页岩以石英和黏土矿物为主,其中黏土矿物以伊利石和伊/蒙混层为主。硬脆性页岩虽不含有蒙脱石,但伊/蒙混层含量比较高,其还是能表现出一定水化膨胀性； (2)通过润湿性测试及比表面积测试发现,页岩的低比表面积和水湿性可知岩石是很容易发生水侵现象；同时通过电子电镜扫描可看出,硬脆性页岩微裂隙、微孔隙及层理发育,钻井液滤液很容易沿着层理面以及微裂缝侵入到岩石内部,加剧水化作用。而声波测试也证明了钻井液滤液改变了岩石内部结构。 (3)通过岩石力学实验研究了水化作用对硬脆性岩石的强度、硬度等影响,结果表明水化作用将使硬脆性页岩强度及硬度降低,其下降幅度随着水化程度的加深而减小。 (4)根据浸泡岩石的三轴力学实验得到的浸泡之后岩石强度参数,,并通过对目标地层页岩物性、力学特性分析,建立直井井壁坍塌压力计算模型,分析了水化作用对坍塌压力的影响。结合以上研究内容发现硬脆性页岩地层层理微裂缝、微裂隙发育,在钻井液方面需要钻井液具有较强的封堵性能以及失水控制能力。尽量避免水或其他液相沿裂缝或裂纹侵入,是该类地层钻井液防塌的关键。
[Abstract]:In recent years, with the increasing demand for oil and natural gas resources in China, major oil companies have also increased the intensity of shale gas exploration and development. However, the problem of wellbore stability in hard and brittle shale formation has always been the technical bottleneck restricting the safe and efficient exploitation of deep oil and gas resources, especially the influence of hydration on the stability of hard brittle shale wellbore. In order to reveal the mechanism of wellbore instability in hard brittle shale formation, a laboratory study of hard brittle shale was carried out in a study area, including mineral composition, specific surface area, wettability and cation exchange capacity. The influence of immersion drilling fluid on the strength characteristics of hard brittle shale was studied by microstructure and triaxial compression test. Based on the above tests, the physical and chemical properties and mechanical characteristics of hard brittle shale were obtained. The cause of shale formation wall instability caused by shale itself and the influence of hydration on the instability of hard brittle shale shaft wall are analyzed. Based on the shale mechanical properties and the stress around the well, the collapse of the straight well in the research area is established. Collapse pressure calculation model, The influence of drilling fluid immersion time on collapse pressure is analyzed. 1) the hard brittle shale in the study area is mainly composed of quartz and clay minerals, and the clay minerals are mainly Illite and Illite / montmorillonite. Although the hard brittle shale does not contain montmorillonite, the content of Iraq / montmorillonite is relatively high. It can still show a certain hydration expansion; (2) through wettability test and specific surface area test, the low specific surface area and water wettability of shale show that the rock is easy to be invaded by water, at the same time, the micro-fracture, micropore and stratification of hard and brittle shale can be seen by scanning electron microscope. Drilling fluid filtrate can easily invade the rock along the stratigraphic surface and microfracture, and the hydration is aggravated. The sonic test also proves that the drilling fluid filtrate changes the internal structure of the rock. 3) the effect of hydration on the strength and hardness of hard brittle rock is studied by rock mechanics experiment. The results show that hydration will reduce the strength and hardness of hard brittle shale, and the decreasing range will decrease with the deepening of hydration degree. 4) according to the rock strength parameters obtained from the triaxial mechanical experiment of immersed rock, and through the analysis of the physical properties and mechanical properties of the target shale, a model for calculating the collapse pressure of the vertical well wall is established. The influence of hydration on collapse pressure was analyzed. Combined with the above research contents, it is found that the hard and brittle shale strata have microfractures and microfractures. It is necessary for drilling fluid to have strong plugging performance and water loss control ability in drilling fluid. It is the key to prevent sloughing of drilling fluid in this kind of formation to avoid water or other liquid phase intrusion along fracture or crack as far as possible.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE254

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