四川南江中二叠统栖霞组白云岩岩石学特征

发布时间：2018-06-01 04:27

本文选题：南江桥亭 + 中二叠统栖霞组　；参考：《成都理工大学》2015年硕士论文

【摘要】：白云岩储层是碳酸盐岩的主要储层类型之一,中石油西南油气田分公司目前在四川盆地中二叠统已经发现了具有工业价值的白云岩储层气藏,充分显示了这些白云岩储层在油气勘探中的良好前景。前人对于四川盆地栖霞组地层的古生物特征、沉积相、层序地层以及成岩作用等方面都开展了大量的工作并取得了丰硕的研究成果,但关于白云岩的研究成果更多的集中在四川盆地西部,川东北地区栖霞组地层中有关白云岩的研究显得相对薄弱。因此,本文以川东北南江桥亭中二叠统栖霞组白云岩为研究对象,通过野外露头观察、薄片鉴定、阴极发光特征、扫描电镜和能谱分析、X衍射分析等方法,研究了岩石学特征、白云石有序度特征及影响因素、成岩流体性质等,并结合前人关于川东北地区地质背景、发育地层、沉积相、埋藏史和热史等研究,对南江桥亭栖霞组白云岩成因进行一些有价值的探讨。通过对比研究南江桥亭剖面、广元长江沟剖面以及吴家1井、矿2井、汉深1井栖霞组白云石有序度得出:①白云石的有序度与其结晶程度有关,晶体相对较大(如粗-中晶)的白云石有序度好于晶体相对较小(如细晶)白云石;②白云石有序度与碳酸盐岩白云岩化程度有关,白云岩化越彻底,白云石的有序度越高;③白云石有序度与Fe2+、Mn2+、Sr2+离子含量有关,Fe2+、Mn2+、Sr2+离子含量与白云石有序度呈负相关关系。3口井下样品白云岩化比南江桥亭和广元长江沟剖面更彻底,白云石有序度更高;其中西南部的汉深1井白云石有序度最高,东北部的南江桥亭剖面白云石有序度最低,这种变化趋势也反映了热事件的影响,离热源(峨眉玄武岩)越远,白云岩化作用越弱。栖霞组白云岩化作用不彻底,主要发育的是灰质白云岩。白云岩不具原始结构,为中细晶白云岩,晶形以平直晶面半自形-非平直晶面它形晶为主,此外还有平直晶面斑状晶等以及最具特色的非平直晶面鞍形晶。白云岩中发育一些特殊组构,如切割白云石的浅-中埋藏环境形成的缝合线或者裂缝,非平直晶面白云石的破裂和溶解,具有热液成因指向意义的鞍形白云石;还发现一些与热液作用有关的自生非碳酸盐矿物,如萤石、氟磷灰石、钠长石、黄铁矿等,这些特殊组构和矿物的发现进一步证明了南江中二叠统白云岩的热液成因。白云石阴极发光强度较弱,主要发粉红色光,方解石发暗红色光或不发光,成岩流体总体上表现为近似海源流体性质,同时存在外源流体的混入。再结合前人研究的埋藏史及热史,我们认为南江桥亭栖霞组白云岩的成因与峨眉山玄武喷发引起的热事件有关,温度升高克服了白云石形成的动力学屏障,热作用的时间较短导致白云岩化作用不彻底。
[Abstract]:Dolomite reservoir is one of the main carbonate reservoir types. The PetroChina Southwest Oil and Gas Field Branch has discovered dolomite reservoir with industrial value in the Middle Permian in Sichuan Basin. These dolomite reservoirs have a good prospect in oil and gas exploration. Previous studies on the paleobiological characteristics, sedimentary facies, sequence stratigraphy and diagenesis of Qixia formation in Sichuan Basin have made great achievements. But the research results of dolomite are more concentrated in the western part of Sichuan basin, and the study of dolomite in Qixia formation strata in northeast Sichuan is relatively weak. Therefore, in this paper, the petrological characteristics of Qixia formation of the Middle Permian in Jiangqiao Pavilion, East and South Sichuan, are studied by means of field outcrop observation, sheet identification, cathodoluminescence, scanning electron microscopy and X-ray diffraction analysis. The characteristics of dolomite orderliness and influencing factors, diagenetic fluid properties, etc., combined with previous studies on geological background, stratigraphic development, sedimentary facies, burial history and thermal history in northeast Sichuan, Some valuable discussions on the origin of dolomite in Qixia formation of Nanjiang Bridge are carried out. Through comparative study of the dolomite order degree of Qixia formation in Nanjiangqiao section, Guangyuan Yangtze River section, Wujia-1 well, No. 2 well and Qixia formation, the orderliness of dolomite is related to the degree of crystallization. The orderliness of dolomite with larger crystal (such as coarse-mesocrystalline) is better than that with relatively small crystal (such as fine crystal) dolomite is related to the dolomitization degree of carbonate rock. The more complete dolomitization, the higher the orderliness of dolomite; (3) the orderliness of dolomite is related to the content of Fe2 mn _ 2 and Sr _ 2 ions. There is a negative correlation between the content of Fe _ 2H _ 2O _ 2 mn _ 2 and the orderliness of dolomite. 3.The dolomitization of downhole samples is more thorough than that of Nanjiang Qiaoting and Guangyuan Yangtze River Gully, and the orderliness of dolomite is higher. The dolomite order of Hanshen 1 well in the southwest is the highest, and the dolomite order is the lowest in the Nanjiangqiao Ting section in the northeast. This trend also reflects the influence of thermal events. The farther away from the heat source (Emei basalt), the weaker dolomitization. The dolomitization of Qixia formation is not thorough, and the main development is gray dolomite. The dolomite has no original structure and belongs to the medium and fine grain dolomite. The crystal shape is mainly composed of flat crystal face semi-automorphism and non-flat straight crystal plane. In addition, there are porphyry crystal of flat straight crystal plane and saddle crystal of the most characteristic non-straight crystal plane. There are some special structures in dolomite, such as suture or fracture formed in shallow-middle burial environment of cutting dolomite, rupture and dissolution of dolomite with non-straight crystal plane, and saddle-shaped dolomite with hydrothermal origin. Some authigenic non-carbonate minerals related to hydrothermal processes, such as fluorite, fluoroapatite, albite, pyrite and so on, are also found. The discovery of these special fabrics and minerals further proves the hydrothermal genesis of dolomite in the Middle Permian in Nanjiang. Dolomite cathodoluminescence intensity is weak, mainly pink light, calcite dark red light or no luminescence, diagenetic fluid is generally similar to the characteristics of sea source fluid, and there is a mixture of exogenous fluids. Combined with the burial history and thermal history of previous studies, we think that the origin of dolomite in Qixia formation of Nanjiang bridge is related to the thermal events caused by Black Tortoise eruption in Emei Mountain, and the rise of temperature overcomes the dynamic barrier of dolomite formation. The short time of thermal action leads to incomplete dolomitization.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13

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