Abstract: Low-porosity, ultra-low permeability volcanic reservoirs with strong heterogeneity are developed in the Upper Carboniferous Harjiawu Formation and Karagang Formation in the Niujuanhu-Niudong structural belt, Malang sag, Santanghu Basin. Based on systematically analyzing the type, content, occurrence state, distribution characteristics, genesis and transformation of clay minerals, this paper explores the influence of clay minerals on the physical properties of volcanic reservoirs. The Upper Carboniferous volcanic reservoirs are characterized by ultra-low porosity and permeability, where primary pores are mainly developed, such as vesicular pore, semi-filled amygdule, intercrystalline pores, and intergranular pores, as well as secondary pores such as microcrystalline dissolved pores, matrix dissolved pores, and zeolite dissolved pores. The primary fractures are dominated by condensation contraction joints and contraction joints, and the secondary fractures are mainly shown as tectonic fractures and interlayer fractures. The pore throat structure is dominated by fine pore throat and small pore throat. The Upper Carboniferous volcanic reservoir has medium-high clay mineral content. As the clay mineral content increases, the porosity and permeability of the reservoir decrease. Clay minerals are mainly shown as corroded feldspar minerals, crystal fragments and debris or the diagenetic transformation products of clay minerals. Kaolinite is generally subjected to dissolution, with the development of secondary micropores such as intergranular dissolved pores, and intercrystalline pores in chlorite are well developed, which can effectively improve the reservoir properties of basalt and tuff reservoirs. Illite is mostly filled in intergranular pores, reducing the physical properties of basalt and tuff reservoirs. The chlorite-smectite mixed layer and illite-smectite mixed layer can improve the physical properties of basalt and tuff reservoirs, and are destructive to the physical properties of volcanic breccia reservoirs. The sedimentary areas of basalt and tuff with relatively high contents of kaolinite, chlorite and chlorite-smectite mixed layer are favorable for the development of high-quality reservoirs.

Key words: Malang sag, Upper Carboniferous, volcanic rock, clay minerals, genesis, reservoir physical property

摘要： 三塘湖盆地马朗凹陷牛圈湖—牛东构造带上石炭统哈尔加乌组和卡拉岗组发育低孔、特低渗强非均质性火山岩储层。基于黏土矿物类型、含量、赋存状态、分布特征及其成因与转化的系统分析，讨论了黏土矿物对火山岩储层储集物性的影响。上石炭统火山岩储层为低孔、特低渗储层，主要发育气孔、半充填杏仁孔、晶间孔、粒间孔等原生孔隙和微晶溶孔、基质溶蚀孔、沸石溶孔等次生孔隙，原生裂缝以冷凝收缩缝和收缩节理缝为主，次生裂缝以构造缝、层间缝为主。孔喉结构以微细孔喉—小孔喉为主。上石炭统火山岩储层为中—高黏土矿物含量储层，随黏土矿物含量增加，储层孔隙度、渗透率均降低。黏土矿物主要为长石类矿物、晶屑和岩屑溶蚀成因或黏土矿物成岩转化产物。高岭石普遍遭受溶蚀，发育粒间溶孔等次生微孔，绿泥石晶间孔发育，可有效改善玄武岩和凝灰岩储层的储集物性；伊利石多充填粒间孔隙，降低玄武岩和凝灰岩储层的储集物性；绿/蒙混层和伊/蒙混层对玄武岩和凝灰岩储层储集物性具有改善意义，对火山角砾岩储层储集物性具有破坏性。高岭石、绿泥石和绿/蒙混层相对含量较高的玄武岩与凝灰岩沉积区是优质储层发育有利区。

关键词: 马朗凹陷, 上石炭统, 火山岩, 黏土矿物, 成因, 储层物性