有机质类型分异规律及其主控机制 ——以威远志留系龙马溪组页岩储层为例

页岩储层中的有机质不仅是生成烃类的核心要素,也是生成孔隙的关键因素.前人对于有机质类型的评价表明,不同有机质类型的生烃及成孔能力差异明显.但前人对于有机质类型的识别及评价工作主要以有机地球化学的方式进行有损测试,因此无法在显微尺度上定量评价有机质的类型及含量分布.以四川盆地威远气田志留系龙马溪组页岩储层为例,基于二维大...

Organic Matter Type Differentiation Process and Main Control Mechanism: Case study of the Silurian Longmaxi Formation shale reservoir in Weiyuan area

The organic matter in shale reservoirs is not only the core factor of hydrocarbon generation,but it also generates porosity.Previous evaluations of organic matter types have shown that the hydrocarbon generation and pore formation capacity of the various types of organic matter are significantly different.However,previous identification and evaluation of organic matter types have mainly used organic geochemical procedures for destructive testing,making it impossible to quantitatively evaluate the type and content distribution of the organic matter on a microscopic scale.This study takes as an example the shale reservoirs of the Silurian Longmaxi Formation in the Weiyuan gas field in the Sichuan Basin,focusing on organic matter enrichment in the Long11sub-segment using two-dimensional large-area multi-scale combined SEM to produce images of micro-components.The modular automated processing system(MAPS)technique was used for maceral analysis to quantitatively identify types of organic matter and analyze their vertical distribution.It was found that the organic matter in the Long1₁sub-segment consists mainly of typesⅠandⅡ₁kerogen,with a predominance of typeⅡ₁.The change in organic matter type with depth was determined as a sedimentary facies belt.Sublayers Long 1¹₁and Long1³₁were formed in a stranded anoxic graptolite shale microfacies sedimentary environment.Weak hydrodynamic conditions favored enrichment of typesⅠandⅡ₁kerogen;the Long1²₁and Long1⁴₁sublayers were developed in a low oxygen environment and contain graptolite shale microfacies.Strong hydrodynamic conditions were unfavorable to typesⅠandⅡ₁kerogen enrichment and preservation.