二叠纪峨眉山大火成岩省岩浆喷发是我国显生宙最大的岩浆喷溢事件。四川盆地中二叠世最新油气勘探成果显示,在峨眉山大火成岩省北缘成都-简阳地区,发育大量以火山碎屑岩为主的全新岩性格架。本文首次对该区域岩性格架展开了详细的火山学解译。在优势储集层段中识别出熔结凝灰岩、自碎裂角砾岩和溅积集块岩三类关键岩性,分别形成于溢气爆发-陆上火山碎屑流机制、溢流喷发-自碎裂角砾化机制以及斯通博利-夏威夷涌溅式喷发机制。这是首次对峨眉山大火成岩省中上述岩性的成因机制进行正式确认。在这些岩性中,储集空间以溶蚀孔和交代孔为主。上述岩性的喷发机制,对其储集空间的发育提供了全方位的关键制约因素:(1)有利于产生大量浆源碎屑;(2)堆积方式有利于维持大量相互连通的原生孔隙,使热液流体得以广泛接触碎屑堆积骨架;(3)堆积于火口近源区域,受异常热流值作用强,有助于维持流体的高效活性。上述三方面最终导致流体对岩石骨架进行深刻的溶蚀交代改造,为规模性储集体发育奠定前提。

The Permian Emeishan Large Igneous Province represents the aftermath of the most significant Phanerozoic volcanic eruption in China. Recent petroleum exploration within the middle Permian system of the Sichuan Basin has unveiled novel volcaniclastic architectures in the Chengdu-Jianyang Area, situated at the northernmost edge of the Emeishan Large Igneous Province. This study introduces a comprehensive interpretation of the lithology and petrography of these architectures, identifying three primary lithological series: the ignimbrite series, the autoclastic series, and the agglomerate series within the reservoir section. It is proposed that these series originate from terrestrial pyroclastic flows, autobrecciation of effusive lavas, and Strombolian-Hawaiian fire fountaining spattering, respectively. These mechanisms are conclusively established for the first time in this region. The predominant pore spaces within these lithologies are characterized by dissolved and intercrystalline pores formed during alteration processes. The genesis of these lithologies imposes essential constraints on the formation of pore spaces, primarily due to: (1) the production of significant juvenile clasts by these mechanisms; (2) the clastic support of the volcaniclasts maintaining substantial initial porosity and permeability, facilitating hydrothermal fluid interaction with the clast framework; and (3) their proximity to volcanic vents, suggesting accumulation under atypical thermal gradients, leading to heightened activity of altering fluids. These factors culminate in substantial rock framework alteration, laying the groundwork for the development of extensive volcanic petroleum reservoirs.