柴达木盆地东部石炭系页岩裂隙突破压力研究

发布时间：2018-05-05 17:01

本文选题：突破压力 + 柴达木盆地　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：突破压力是评价岩石封盖能力的重要参数。页岩作为细粒沉积岩的一种,因为其本身多孔低渗的特点通常认定它具有较高的气体封存效率,在室内研究中这种较高的气体封存效率表现为页岩岩样具有极高的突破压力值。因而页岩地层不但可以广泛的应用于核废料、温室气体的封存,同时也是页岩气生成的有利层位。在一般情况下,完全饱水状态下的页岩岩样突破压力值可以高达40MPa,在实际情况中页岩地层内育有大量的天然裂隙,这些裂隙可能会导致突破压力值相对完整状态下突破压力值小五十倍以上,进而对岩石本身的低渗透率特性造成影响。本文在此基础上,通过对岩样制造工人造裂隙以此来模拟裂隙对石炭系页岩的突破压力的影响。实验中选取了来自zk1-1井中石炭系上统克鲁克组的三块页岩岩样。用线锯对三块岩样进行纵向切割后再次用黏合剂黏合起来从而得到隙宽较小的单一贯通裂隙。运用HA-I型多相流渗透仪在岩样完全饱水状态下,其他条件不变,只改变环压这一单一条件。以此来得到不同环压下带有单一贯通裂隙岩样的突破压力值。同时利用多相流渗透仪注入流体并全程记录过程中上下游压差、流量等数据,结合达西定律及立方定律公式计算得到岩样的裂隙宽度,再通过运用X射线衍射分析方法得到页岩矿物成分相对含量以及运用测量超声波速度的方法得到的该样品的泊松比、弹性模量等力学参数来共同探究裂隙突破压力相对于一般岩石突破压力的不同,探究裂隙这一影响因素对于突破压力的控制作用。通过实验我们测量出人工裂隙大小为16μm-50μm相对一般岩样自然发育裂隙0.13μm-1μm大出约百倍左右。在这些人工裂隙的影响下,裂隙突破压力值最小为0.03MPa,最大值为0.17MPa。相比正常饱水岩样突破压力值呈现出锐减的趋势。结合样品弹性模量这一力学参数、矿物成分分析后得出,裂隙突破压力受到本身粘土矿物含量及弹性模量即刚度的双重影响。岩样自身粘土矿物成分含量高的在饱水状态下粘土矿物发生膨胀可以使岩样在较低环压下保持裂隙宽度变化范围比较小,而岩样自身弹性模量较大的岩样在环压变化下能够保持裂隙宽度相对稳定的变化而不至于在高环压下导致岩样发生形变。本研究研究了裂隙的存在对突破压力的影响,对温室气体等有害气体封存性能评价及页岩气开采过程中水力压裂过程具有重要的现实意义。
[Abstract]:Breakthrough pressure is an important parameter to evaluate the sealing ability of rock. Shale, as one of fine sedimentary rocks, is usually considered to have high gas storage efficiency because of its own porous and low permeability characteristics. In laboratory study, this high gas storage efficiency is shown as the extremely high breakthrough pressure value of shale samples. Therefore, shale formation is not only widely used in the storage of nuclear waste and greenhouse gases, but also a favorable horizon for shale gas generation. In general, the breakthrough pressure of shale rock samples in a fully saturated state can be as high as 40 MPA. In practice, there are a large number of natural fissures in shale strata. These fractures may lead to a breakthrough pressure value of more than 50 times smaller than that of the rock under the condition of relatively complete breakthrough pressure, which will affect the low permeability characteristics of the rock itself. On this basis, the influence of fracture on the breakthrough pressure of Carboniferous shale is simulated by making cracks on rock samples. Three shale samples from the Carboniferous upper Kruke formation in zk1-1 well were selected. Three rock samples were cut longitudinally by wire saws and then bonded with binder to obtain a single perforated fracture with small gap width. Under the condition that the rock samples are completely saturated with water, the other conditions remain unchanged and only the ring pressure is changed by using the HA-I multiphase flow osmometer. The breakthrough pressure values of rock samples with a single through fracture under different ring pressures are obtained. At the same time, the fracture width of rock sample is calculated by using multiphase flow permeator to inject fluid and record the data of pressure difference and flow rate in the whole process, combined with Darcy's law and cubic law formula. The relative content of shale mineral and the Poisson's ratio of the sample obtained by using the method of measuring ultrasonic velocity are obtained by using X-ray diffraction analysis. The mechanical parameters such as modulus of elasticity are used to explore the difference of fracture breakthrough pressure compared with the general rock breakthrough pressure, and the controlling effect of fracture on breakthrough pressure is explored. The artificial fracture size of 16 渭 m to 50 渭 m is about 100 times larger than that of natural developed fractures of 0.13 渭 m ~ (-1) 渭 m in normal rock samples. Under the influence of these artificial fissures, the fracture breakthrough pressure is 0.03MPa and the maximum is 0.17MPa. Compared with the normal saturated rock samples, the breakthrough pressure values show a trend of sharp decrease. According to the mechanical parameter of elastic modulus of the sample and the analysis of mineral composition, it is concluded that the fracture breaking pressure is affected by the content of clay minerals and the elastic modulus, that is, the stiffness. The swelling of clay minerals with high content of clay minerals in rock samples can make rock samples keep crack width variation range smaller under lower ring pressure. However, the rock samples with larger elastic modulus can keep the fracture width relatively stable under the ring pressure change, and not cause the rock samples to deform under the high ring pressure. In this paper, the influence of the existence of cracks on breakthrough pressure is studied. It is of great practical significance to evaluate the storage performance of harmful gases such as greenhouse gases and hydraulic fracturing in shale gas extraction.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU45

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