花岗岩侵入对页岩成分和孔隙结构的影响

发布时间：2018-04-27 23:28

本文选题：页岩 + 接触变质作用　；参考：《南京大学》2016年硕士论文

【摘要】：页岩气可以吸附或以游离态赋存在富有机质泥页岩及其夹层中,具有自生、自储、自盖的成藏特征。近年来,随着水平钻井技术和水力压裂等开发技术的快速发展,低孔、低渗的页岩气页岩气藏开发已成为可能。页岩的孔隙结构是页岩气勘探开发中的关键问题,同时后期保存条件,尤其是构造活动和岩浆作用是页岩储层评价的重要指标。因此,本文系统分析了页岩孔隙特征的研究方法和分类方案,并总结了下扬子地区古生界的页岩孔隙特征。为探讨岩浆侵入对泥页岩的影响,选择典型剖面-浙西安吉罗村剖面对荷塘组页岩矿物组成、有机地化及孔隙结构等方面进行了详细研究。图像观察法和物理测量法是页岩孔隙结构的常用研究手段。结合图像处理软件,图像观察法(如扫描电镜、透射电镜、原子力显微镜等等)可获得孔隙形态和分布等信息。压汞法、气体吸附分析、核磁共振法等物理测量法可获得统计意义上的页岩孔隙大小、分布、孔隙率、比表面积等信息。基于研究手段的不同,页岩孔隙具有三种分类方式,基于图像观察法的分类(粒间孔、粒内孔、有机质孔隙及微裂隙)、基于物理测量法的分类(微孔、中孔及小孔)及产状—结构分类方案(图像观察与物理定量分类相结合)。下扬子地区古生界(荷塘组、胡乐祖及宁国组)页岩的孔隙结构主要孔隙类型主要为粒间孔、粒内孔和有机质粒内孔,孔径范围为0.084-36.5μm,平均约1.04μm,中孔占50%以上。接触变质作用会显著改变页岩矿物组成、有机地化及孔隙结构等多方面的特征。为分析这种火成岩侵入对页岩的热效应,我们对浙西北安吉罗村被花岗岩侵入的荷塘组硅质页岩展开了详细的有机地球化学与显微组构研究。与未被岩浆侵入的南京幕府山剖面粉砂质泥岩相比,罗村剖面荷塘组页岩硅化严重,分布条带状的黑色炭质残余。越靠近岩体,粘土矿物含量减少,硅质泥岩的等效镜质体反射率从2.6%增大至3.7%,表明岩浆侵入体的存在加速了有机质的成熟。但是总有机碳(TOC)和侵入距离却未见明显相关性。根据等效镜质体反射率的变化,接触变质晕宽度约为岩墙宽度的37%。罗村剖面荷塘组硅质页岩的孔隙类型主要为粒间孔、粒内孔和较大孔径(50nm)的有机质粒内孔。随着侵入距离的减小,中孔和微孔孔隙体积均减小,页岩的比表面积从5.22m2/g降至0.16m2/g。然而,岩浆作用的热膨胀导致大孔和微裂隙的产生,提高了硅质页岩孔隙的渗透率,可造成页岩气的快速逃逸。因此花岗玢岩带来的热和硅质流体改变了页岩的矿物组成和孔隙结构,不利于接触变质晕范围内的页岩气的保存。
[Abstract]:Shale gas can be adsorbed or stored in organic clay shale and its intercalation in free state, which has the characteristics of self-generation, self-reservoir and self-cap. In recent years, with the rapid development of horizontal drilling technology and hydraulic fracturing technology, the development of shale gas shale gas reservoirs with low porosity and low permeability has become possible. The pore structure of shale is a key problem in shale gas exploration and development. At the same time, the late preservation conditions, especially tectonic activity and magmatism, are important indicators of shale reservoir evaluation. Therefore, this paper systematically analyzes the research methods and classification schemes of shale pore characteristics, and summarizes the shale pore characteristics of Paleozoic in Lower Yangtze area. In order to study the influence of magmatic intrusion on shale, the mineral composition, organic geochemistry and pore structure of the Hetang formation shale were studied in detail by selecting the typical profile-Ananluocun section in western Zhejiang. Image observation and physical measurement are commonly used to study shale pore structure. In combination with image processing software, image observation (such as scanning electron microscope, transmission electron microscope, atomic force microscope, etc.) can obtain information of pore morphology and distribution. Physical measurement methods, such as mercury injection, gas adsorption analysis and nuclear magnetic resonance, can be used to obtain statistical information of shale pore size, distribution, porosity and specific surface area. There are three types of classification of shale pores based on different research methods: those based on image observation (intergranular pore, intragranular pore, organic pore and microfissure), and based on physical measurement (micropore, micropore, micropore). Mesopore and micropore) and production-structure classification scheme (image observation combined with physical quantitative classification). The main pore types of Paleozoic shale in Lower Yangtze area (Hetang formation, Hu Lechu and Ningguo formation) are intergranular pore, intragranular pore and organic plasmid pore. The pore size ranges from 0.084-36.5 渭 m, with an average pore size of 1.04 渭 m, accounting for more than 50% of the pore size. Contact metamorphism can significantly change the shale mineral composition, organic geochemistry and pore structure. In order to analyze the thermal effect of the igneous rock intrusion on shale, we have carried out a detailed study of the organic geochemistry and microfabric of the Heitang formation siliceous shale, which was invaded by granite in Angelo village, northwest of Zhejiang Province. Compared with the silty mudstone in the Shoufushan section of Nanjing without magma intrusion, the shale of the Hetang formation in the Luocun profile is silicified seriously, and the black carbonaceous remains are distributed in stripes. The content of clay minerals decreases and the equivalent vitrinite reflectance of siliceous mudstone increases from 2.6% to 3.7 indicating that the existence of magmatic intrusion accelerates the maturation of organic matter. However, there was no significant correlation between total organic carbon (TOC) and invasion distance. According to the change of equivalent vitrinite reflectance, the width of contact metamorphic halo is about 37% of the width of rock wall. The pore types of siliceous shale in Houtang formation of Luocun section are mainly intergranular pore, intragranular pore and large pore size 50 nm). With the decrease of invasion distance, both mesoporous and microporous pore volumes decrease, and the specific surface area of shale decreases from 5.22m2/g to 0.16 m2 / g. However, the thermal expansion of magmatism leads to the formation of macropores and microcracks, which increases the permeability of siliceous shale pores and causes the rapid escape of shale gas. Therefore, the thermal and siliceous fluids brought by granitic porphyrite change the mineral composition and pore structure of shale, which is not conducive to the preservation of shale gas in the range of contact metamorphic halo.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P618.13

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