摘要
为明确火山活动控制陆相含油气盆地优质烃源岩发育的作用机制，对古今火山、碱湖以及优质烃源岩这三者的相互联系进行广泛的文献调研，认为碱湖是联系火山活动与优质烃源岩发育的中间场所。火山活动喷发的CO进入热液、地下水或河流中，加速硅酸盐水解，产生大量HCO，输入湖泊中导致水体pH值升高，形成碱湖。而碱湖中高pH值可以活化Mo、磷酸盐和硅酸盐等多种营养元素和化合物，提高水体的初级生产力；同时也可以使硅质在水体中的溶解度呈指数增大，这种溶解的硅质在有机质初始降解等pH值降低过程中易发生沉淀，形成硅质保护层，避免有机质的进一步降解。由此提出火山活动-碱湖-优质烃源岩的成因链模式，该模式形成的页岩油气储集层微晶白云石等矿物含量高，凝灰物质易发生蒙脱石-沸石-钾长石-钠长石转变，可以有效增加页岩油气储集层的脆性和微孔隙。
Abstract
In order to clarify the controlling mechanisms of volcanic activities on the development of high-quality source rocks in non-marine petroliferous basins, this study summarizes the relationships between volcanic activity, alkaline lakes and high-quality source rocks through an extensive review of previous studies and proposes that alkaline lakes act as a vital link between volcanic activities and source rocks. It is suggested that large amount of CO emitted by volcanic activities would enter hydrothermal fluids, underground waters or rivers and then produce a large amount of HCO through accelerated silicate hydrolysis process, leading to the formation of alkaline lakes. The high pH in alkaline lakes would activate a variety of nutrient elements and compounds such as Mo, phosphate and silicate, thus improving the primary productivity of water body. In addition, the high pH also would lead to an exponential increase of silica solubility in alkaline waters. During the process of pH decrease by initial degradation of organic matter, the dissolved silica would precipitate and form a siliceous layer, which could effectively prevent further degradation of organic matter. Based on these assumptions, this study proposes a genetic model for volcanism-alkaline lake-high-quality source rocks chain, which is the main reason of the occurrence of brittle and porous shale reservoirs for oil due to a high content of microcrystalline dolomite and tuff materials that are easily converted from montmorillonite to zeolite, potassium feldspar, and sodium feldspar.
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