| 基于岩石薄片的鲕粒碳酸盐岩地球化学溶蚀 |
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| 引用本文： | 方旸,谢淑云,何治亮,刘银,鲍征宇,沃玉进,张殿伟.基于岩石薄片的鲕粒碳酸盐岩地球化学溶蚀[J].地球科学,2016,41(5):779-791. |
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| 作者姓名： | 方旸 谢淑云 何治亮 刘银 鲍征宇 沃玉进 张殿伟 |
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| 作者单位： | 1.中国地质大学地球科学学院，湖北 武汉 430074 |
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| 基金项目： | 国家重大专项项目2008ZX05005国家重点基础研究发展计划(973计划)项目2012CB214802中国石油化工股份有限公司项目P14038 |
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| 摘 要： | 为了更好地认识鲕粒灰岩及鲕粒云岩的溶蚀机制，并指导油气勘探，通过岩石薄片溶蚀模拟实验，结合环境扫描观察和能谱分析进行原位微观形貌观察和分析，并采用分形与多重分形对能谱面扫描图像进行分析.实验结果显示，硫酸介质下鲕粒灰岩溶蚀从结构缺陷点(解理或裂隙)开始，钙含量高的点溶蚀速率快，而钙含量低的点和含硅部分溶蚀慢或不溶蚀，从而形成凹凸不平的溶蚀坑孔隙空间；而鲕粒云岩在硫酸介质中的溶蚀从白云石晶体间裂隙开始，这是因为颗粒及颗粒间有大量微裂隙.相同条件下，鲕粒云岩的溶蚀丢失质量比鲕粒灰岩多出约80%，这表明硫酸介质对白云岩具有更强的溶蚀能力.通过对溶蚀微观形貌的观察发现，硫酸对鲕粒白云岩结构的破坏作用而形成的颗粒状表面，更有利于溶蚀作用的深入进行，进而发育优质孔隙.此外，分形与多重分形分析结果表明，碳酸盐岩薄片表面的Ca、Mg、Si含量分布的非均质性的差异控制着溶蚀反应，成分差异大、元素含量非均质性强能促进溶解反应的进行.
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| 关 键 词： | 碳酸盐岩储层 岩石薄片 差异溶蚀 多重分形 地球化学 |
| 收稿时间： | 2015-11-12 |
Thin Section-Based Geochemical Dissolution Experiments of Ooid Carbonates |
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| Abstract: | To explore the law of carbonate dissolution evolution to facilitate oil and gas exploration, the dissolution process and kinetic mechanisms of oolitic limestone and oolitic dolomite in sulfuric acid medium under normal temperatures are discussed in the paper. In-situ micromorphology of the reaction surface was observed by environmental scanning electron microscope (ESEM) and the elemental distribution was analyzed by fractal and multifractal theory using the X-ray mapping capabilities of the ESEM. The different dissolutions observed in the experiment indicate that the dissolution of the mineral starts at points of structure defects (as cleavage or fracture), and that the dissolution rate of oolitic limestone at the point with high Ca content is faster than that with low Ca or high Si content, which results in an uneven corrosion pits and pore spaces formed on the reaction surface. Moreover, the sulfuric acid cracks the ooid dolomite into granular and intergranular fractures and pore space in or between particles. Analysis of the weight loss by dissolution of thin section shows that the weight loss of oolitic dolomite is about 80% higher than that of oolitic limestone, indicating that the sulfuric acid has a stronger dissolution ability for oolitic dolomite. It is found by micromorphology observation that the granular surface of oolitic dolomite formed by sulfuric acid dissolution is more conducive to deepening of dissolution, which further improves development of pore space and connectivity. The fractal and multifractal analyses indicate that the dissolution process is controlled by differences between the element distribution heterogeneity of Ca, Mg and Si. Additionally, large difference of composition, strong heterogeneity of element distribution can promote the dissolution reaction. |
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