湘西北页岩气储层的可压裂性评价

发布时间：2018-11-28 17:11

【摘要】：页岩气全球资源量巨大,具有勘探开发的潜力。国内外学者对于页岩气的富集机理和条件、有利优先区选择等进行了较多的研究,但是对于储层改造方法和技术、页岩气储层的可压裂性研究较少。本文对湘西北牛蹄塘组页岩气储层特征进行试验研究和理论分析,从定性和定量的角度评价其可压裂性,所开展的工作主要有:(1)开展了湘西北页岩气储层地质特征的研究。地质踏勘结果显示,牛蹄塘组页岩岩性为黑色炭质板岩,粉砂质炭质板岩,深灰、灰黑色薄层硅质岩;通X衍射仪分析了页岩的矿物组成,结果表明页岩脆性矿物含量平均为63.6%,在同类水平中较高,黏土矿物相对较低,平均含量为29.4%,主要以伊利石为主,含少量高岭石;通过扫描电镜观察了湘西北牛蹄塘组页岩气储层的微观结构,分析表明页岩微裂缝高度发育,同时含有大量呈蜂窝状和草莓状的小孔洞,孔缝系统密度高。(2)开展了湘西北页岩气储层物理力学特性的研究。物理试验研究表明页岩的天然密度在2.16g/cm~3~2.46g/cm~3之间、含水率和饱和吸水率平均值分别为0.615%和0.888%;页岩单轴抗压强度在78.04MPa~161.23MPa之间,杨氏模量和泊松比平均值分别为31.8GPa和0.23,应力-应变曲线没有明显的塑性变形段和屈服点,属于典型脆性破坏;三轴试验结果表明页岩在不同围压下破坏模式为剪切破坏,应力峰值强度在234.429MPa~324.478MPa之间;页岩在劈裂破坏时,抗拉强度极低在4.10MPa~15.14MPa之间,呈现沿中轴线径向产生张拉破坏特征。(3)建立了可压裂性评价模型。论文提出了利用页岩脆性系数、脆性矿物含量、黏土矿物含量和粘聚力几个关键指标定量评价湘西北页岩的可压裂性,运用层次分析法原理计算不同指标的权重系数,并使用极差变换法将参数标准化到0~1之间的无量纲常数,基于物理力学试验提供的基础数据计算出湘西北页岩气储层可压裂性系数为0.5,根据可压裂性系数的分级以及与胜利油田页岩可压裂性的对比分析,湘西北页岩气储层的可压裂性处于中等偏上水平。
[Abstract]:Shale gas is a huge resource in the world and has the potential of exploration and development. Scholars at home and abroad have done a lot of research on the accumulation mechanism and conditions of shale gas and the selection of favorable priority areas. However, there is little research on the fracturing ability of shale gas reservoirs in terms of reservoir modification methods and techniques. In this paper, the characteristics of shale gas reservoir of Niutetang formation in northwest Hunan are studied and analyzed in theory, and its fracturing ability is evaluated from qualitative and quantitative aspects. The main works are as follows: (1) the geological characteristics of shale gas reservoirs in Northwest Hunan are studied. The geological exploration results show that the shale rocks of Niulitang formation are black carbonaceous slate, silty carbonaceous slate, deep ash and gray black thin layer siliceous rocks. The mineral composition of shale is analyzed by X-ray diffraction. The results show that the average content of brittle minerals in shale is 63.6, which is higher in the same level, the clay mineral is relatively low, and the average content is 29.40.Illite is the main content. Contains a small amount of kaolinite; The microstructure of shale gas reservoir of Niutetang formation in northwestern Hunan Province was observed by scanning electron microscope. The analysis shows that the shale microfractures are highly developed and contain a large number of honeycomb and strawberry shaped small pores. The density of porosity and fracture system is high. (2) the physical and mechanical properties of shale gas reservoir in Northwest Hunan are studied. The physical tests show that the natural density of shale is between 2.16g/cm~3~2.46g/cm~3 and the average values of water content and saturated water absorption are 0.615% and 0.888% respectively. The uniaxial compressive strength of shale is between 78.04MPa~161.23MPa, the average values of Young's modulus and Poisson's ratio are 31.8GPa and 0.23, respectively. The stress-strain curve has no obvious plastic deformation section and yield point, so it belongs to typical brittle failure. The results of triaxial tests show that the failure mode of shale under different confining pressures is shear failure and the peak stress intensity is between 234.429MPa~324.478MPa; The tensile strength of shale is very low between 4.10MPa~15.14MPa and fracturing failure. (3) the fracturability evaluation model is established. In this paper, the fracturability of northwest Hunan shale is evaluated quantitatively by using the key indexes of shale brittleness coefficient, brittle mineral content, clay mineral content and cohesive force, and the weight coefficient of different indexes is calculated by using the principle of analytic hierarchy process (AHP). Using the range transformation method to standardize the parameters to 0 ~ 1, the fracturing coefficient of shale gas reservoir in northwest Hunan is calculated to be 0.5 based on the basic data provided by physical and mechanical tests. According to the classification of fracturing coefficient and the comparison with the fracturing ability of shale in Shengli Oilfield, the fracturing ability of shale gas reservoir in northwest Hunan is at the middle level.
【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE377

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