旺苍地区灯影组层状硅质岩类孔洞充填特征

Pore-infillings in Stratiform Siliceous Rocks of the Dengying Formation in Wangcang Area, Northern Sichuan Basin

刘小洪 石章俊 冯明友 王良军 王兴志

LIUXiaohong SHIZhangjun FENGMingyou WANGLiangjun WANGXingzhi

西南石油大学地球科学与技术学院, 四川 成都 610500 中国石化勘探分公司, 四川 成都 610041

School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan 610500, China SINOPEC Exploration Company, Chengdu, Sichuan 610041, China

为揭示旺苍地区灯影组层状硅质岩类溶蚀孔洞中矿物充填序列及流体作用过程，综合应用岩石学及地球化学分析测试方法进行研究。结果表明，硅质岩类溶蚀孔洞中具白云石、方解石、微晶石英—纤维状玉髓、细—中晶石英及粗—巨晶石英5个世代典型矿物充填并历经6期流体作用影响。在早期硅质岩形成基础上，第I期深盆富镁热液溶蚀—充填叠加改造形成鞍状白云石；第II期含硅热液交代白云石形成亮晶方解石；在第III期沥青形成后，第IV期为封闭体系下高浓度低温硅质热液快速沉淀出微晶石英—纤维状玉髓；第V期为石炭—二叠纪硅质流体作用下沉淀出细晶—中晶石英；第VI期为三叠纪弱饱和二氧化硅水溶液近平衡条件下沿缝洞缓慢结晶沉淀出粗晶—巨晶石英。经深盆富镁热液叠加硅质热液对层状硅质岩类复合改造，部分微孔及裂缝发育的硅质岩类可成为潜在储层。

Dissolution pores within stratiform siliceous rocks of the Sinian Dengying Formation in Wangcang Area (Northern Sichuan) are filled with multistage minerals. Petrological and geochemical analyses are conducted to reveal the filling sequence of minerals and elucidate the process of fluid interaction. The results show that dolomite, aphanitic-fibrous chalcedony, fine-mesocrystalline quartz and coarse-megacrystalline quartz are typical fillings in the dissolution pores of siliceous rocks, corresponding to six episodic fluid events. After formation of early siliceous rocks, semi-filling saddle dolomite was formed by the dissolution-filling superposition of magnesium-rich hydrothermal fluid derived from deep basin in the first stage. Sparry calcite was formed during the second stage by replacement of siliceous hydrothermal fluid. In the third stage, asphalt was formed in the Silurian to Devonian. Hereafter, the microcrystalline quartz and fibrous chalcedony were formed by hydrothermal solution in closed system during the fourth stage. The fine-mesocrystalline quartz and coarse-megacrystalline quartz were precipitated in the fifth stage and sixth stage, respectively. The fine-mesocrystalline quartz was formed by siliceous fluids during the Carboniferous to Permian, and the coarse-megacrystalline quartz was formed by weak-saturated silica aqueous precipitation along fracture or near-equilibrium conditions in the pores during the Triassic. The superimposition of magnesium-rich hydrothermal fluids and siliceous hydrothermal processes in deep basins can improve stratiform siliceous rocks, and some siliceous rocks with dolomite moldic pores and fractures are suspective special reservoirs.

10.11885/j.issn.16745086.2019.09.03.01