川西南部周公山地区峨眉山玄武岩有利储层分析

川西雅安地区周公山构造周公2井玄武岩取心较长、较完整,并且其紧邻高产气井——周公1井,是研究玄武岩气藏的典型井。以岩石学特征为基础,宏观和微观相结合,从岩心、电性、物性、微观特征入手将周公2井取心段峨眉山玄武岩中储层段岩石学特征、孔隙类型、流体特征及其纵向上的分布发育特征进行归纳总结并与1井产层段进行了对比研究。分析认为,川西南部地区玄武岩有利储层分布于2处,一处为顶部普遍发育的数米厚风化壳,另一处是旋回中上部的富含杏仁体角砾化玄武岩。第二类储层中发育沥青并伴随发育石英,溶孔、溶洞、裂缝普遍,但渗透率较小;其有效储集空间大多数由次生作用产生,喷溢间歇期的构造作用、风化及溶蚀作用良好的匹配关系至关重要;后期形成的构造裂缝与垂直于层面的节理缝较易形成开放体系,极可能就是破坏周公2井气藏保存条件的主要因素。

Favorable reservoir analysis of Emeishan basalt in Zhougongshan area of southwest Sichuan Province

The Zhougong 2 well that drilled Emeishan basalt of Zhougongshan structure in Ya''an area of western Sichuan is a typical well in basalt gas reservoirs, whose core is relatively long, fairly complete and close to the high-yield well Zhougong 1 well. Based on the petrological characteristics, the combination of macroscopic and microscopic phenomena and starting with the core, electrical, physical, and microscopic characteristics of Emeishan basalt reservoir in Zhougong 2 well core, the authors summarized its petrological characteristics, porosity type, fluid features and the distribution in the longitudinal direction in comparison with production intervals of Zhougong 1 well. The results show that the favorable reservoirs of basalt are distributed in two intervals in southwest Sichuan: one is the weathering crust, which is extensively developed at the top with the thickness of a few meters, and the other is the amygdale-rich brecciated basalt in the upper part of the cycle. The second type of reservoir has well-developed asphalt associated with quartz and extensive dissolved pores, caves and cracks, but with less permeability; the majority of its efficiency reservoir space was generated by the secondary actions. The good matching relationship between tectonism in the dormant period of eruption and the weathering and dissolution is of great importance. The open system was generally quite easily formed by the aggregation of later period tectonic cracks and joint fissures perpendicular to the bedding, and this may also be the main factor that has undermined the gas reservoir storage conditions of Zhougong 2 well.