页岩油原位成藏过程及油藏特征——以松辽盆地古龙页岩油为例

In-situ accumulation process and reservoir characteristics of shale oil:A case study of Gulong shale oil in Songliao Basin

为了搞清古龙页岩油成藏过程及油藏特征,指导古龙页岩油勘探开发,利用大量岩心实验分析数据,分析页岩形成的古沉积环境,通过观察大量扫描电镜照片,深入分析有机质赋存状态。以封闭体系低熟页岩生烃热模拟实验为基础,结合成烃—成岩—成储耦合过程研究,系统分析古龙页岩油成藏过程,从而明确其油藏特征。结果表明:(1)青山口组古沉积环境优越,层状藻是古龙页岩有机质的主要来源,古龙页岩原始有机碳含量高,平均在3.0%以上,奠定了页岩油生成的物质基础;(2)古龙页岩有机质主要有3种赋存状态,第1种为有机质和黏土等无机矿物呈互层状分布,第2种为有机质受挤压后在无机矿物粒间赋存,第3种为有机质在黏土矿物层间吸附沉积,有机质的不同赋存状态为古龙页岩的普遍含油奠定了结构基础;(3)古龙页岩油的成藏演化主要经历了压实—大量生烃前阶段、大量生烃阶段、原油裂解等3个阶段;(4)古龙页岩油藏具有大面积连续立体式分布、纯油油藏、压力系统稳定且与埋深关系密切、原油密度和原油黏度受成熟度控制且在平面上呈环带状变化等4个特点。研究成果明确了古龙页岩油成藏过程以及油藏特征,为松辽盆地北部古龙页岩油有利富集区优选以及开发方案设计提供了理论依据。

In order to understand accumulation process of Gulong shale oil and reservoir characteristics to guide the exploration and development of Gulong shale oil,a large amount of core experiment data is used to analyze the paleosedimentary environment of shale formation,many SEM photos are observed to analyze the occurrence states of organic matter,and reservoir characteristics are determined based on thermal simulation experiment for hydrocarbon generation of low maturity shale in closed system and combining with study of hydrocarbon generation-diagenesisaccumulation coupling process.The results show:(1)Paleosedimentary environment of Qingshankou Formation is superior,and laminar algae is the main source of organic matter in Gulong shale.Original organic carbon content of Gulong shale is high,averagely more than 3.0%,being material foundation for shale oil generation.(2)Organic matter of Gulong shale shows 3 main occurrence states,the first kind is interbedded distribution of organic matter and inorganic minerals such as clay,the second kind is organic matter occuring among inorganic mineral grains after being compressed,and the third kind is organic matter adsorbed deposition among clay mineral layers.Different occurrences of organic matter laid the structural foundation for large-scale oil-bearing area of Gulong shale.(3)Accumulation evolution process of Gulong shale mainly experienced 3 stages including compaction stage-stage before massive hydrocarbon generation,massive hydrocarbon generation stage and oil cracking stage.(4)Gulong shale reservoir has 4 characteristics including large area continuous three-dimensional distribution,pure oil reservoir,stable pressure system and closely related to buried depth,and oil density and viscosity controlled by maturity and changed in circular band.The study clarifies the accumulation process and reservoir characteristics of Gulong shale oil,and provides theoretical evidence for optimization and development plan design of favorable enrichment areas of Gulong shale oil in northern Songliao Basin.