侵入岩及其外变质带岩相与储集层模型

The lithofacies and reservoir model of intrusive rock and its exomorphic zones.

由于侵入岩及其外变质带在完全还原条件下成岩 ,其特殊的储集层发育机理正在受到有关学者的关注。研究认为 ,岩浆冷凝、热接触变质作用和水岩反应决定了该复合岩体的基本岩相结构以及储集单元的规模与分布。在这 3种成岩机制作用下 ,岩体中心相、边缘相、角岩相和板岩相 4个亚相带分别具有不同优势的孔缝组合 ,其中 ,石榴石角岩带的粒间孔缝、岩体边缘相的溶蚀孔缝和板岩相的构造裂缝为有利的储集空间类型。活跃的变质热液在该特殊岩相带储集层的形成和演化过程中扮演着极其重要的角色 ,其早期沿热液通道向岩体内部呈透入式溶蚀 ,在还原条件下形成了大量的溶蚀孔缝 ;后期热液碳酸盐充填裂缝 ,导致各亚相带的储集单元之间相互分隔 ,储集层发育间断 ,因此 ,该复合岩体仅在封闭的成岩体系解体以后才能参与围岩的埋藏成岩演化 ,其有效储集空间主要来自早期储集单元在构造或挠曲变形作用下的裂缝连通。

It is believed that there are some special actions to form reservoir spaces, especially the solution pores and cracks in the intrusive rock and its exomorphic zones, because the rock's diagenetic evolution was completed in a reduction environment. It is suggested that three special processes, which are magmatic crystallization, thermodynamic metamorphism and fluid-rock reaction, chiefly decided the lithofacies and reservoir spaces in intrusion rock and its exomorphic zones. There are four subfacies with different types of pore and fissure in the pair of magmatic-host rock. Among their reservoir elements, the interparticle pore and cracks in garnet hornfels, the solution pore and cracks in boundary subfacies, as well as tectonic fractures in slate facies are the major and representative ones. The active metamorphic fluid played an important role in the process forming and developing reservoir space in the pair of rock. At the initial stage, it soluted progressively the minerals to produce a lot of pore and fissure, and then it supplied carbonate to fill the fractures when the metamorphic temperature decreased to 300℃ or lower. As the result, the diagenetic evolution has remained stagnant until the enclosed system has been opened by faults and fractures, which were formed by tectonic or flexure deforming. Therefore, just only the available pore spaces apparel some places, in which seepage elements have been linked up to the pore system of wall rock and connected with each other.