准噶尔盆地南缘柴窝堡凹陷泥页岩地球化学和矿物学特征研究

摘要

Using XRD, Rock-eval and GC-MS, kerogen type, organic geochemical characteristics and inorganic mineralogy features of shales in upper Carboniferous, upper Permian, and lower Jurassi from the Chaiwobu depression at southern margin of Junggar Basin were analyzed. The organic geochemical index shows that from Carboniferous to Permian, it has been a long period of fresh-brackish water sedimentary environment in Chaiwobu depression. The sources of organic matter shared the similar source input characteristics, and kerogen type were mainly featured by type Ⅱ. The thermal evolution of organic matter indicates that shales in lower Jurassic were in low mature stage while shales in upper Carboniferous and upper Permian showed the features of high abundance, rich in types and mature-high mature stage in the thermal evolution. The mineralogical characteristics show that the content of brittle minerals feldspar and quartz in upper Permian shales is 73%, followed by clay mineral, indicating a high brittleness index and good property of fracturing and adsorption. Combined with the previous studies, it is predicted that a certain scale of shale gas resources may be contained in shales of this member with a good prospect and potential for exploration.%利用XRD、Rock-eval和气相色谱—质谱仪对准格尔南缘柴窝堡凹陷上石炭统、 上二叠统及下侏罗统的泥页岩进行了地球化学和矿物学特征分析.有机地球化学实验结果指示,柴窝堡凹陷石炭纪至二叠纪经历了较长时期的淡水—微咸水沉积环境,有机质来源具有相似的母源输入特征,干酪根类型具有Ⅱ型混合母质特征;有机质热演化特征表明,下侏罗统泥页岩处于低熟阶段,上石炭统与上二叠统泥页岩具有机质丰度较高、 有机质类型丰富、 热演化处于成熟—高成熟阶段等特点;矿物学特征显示,上二叠统泥页岩长石、 石英等脆性矿物含量为73%,粘土矿物次之,指示其脆性指数较高,具有较好的可压裂性和粘土表面吸附性.结合前人认识,预测该段泥页岩中可能蕴藏着一定规模的页岩气资源,具有较好的页岩气资源前景和勘探潜力.