摘要
本文针对辽河坳陷西部凹陷古近系沙河街组四段(简称沙四段)混积型页岩油储层,通过氩离子抛光-场发射扫描电镜、二氧化碳吸附实验、低温氮气吸附实验以及高压压汞分析等技术手段,系统研究其孔隙结构特征及优质储层的成因机制。研究发现,研究区沙四段页岩油储层岩性复杂、非均质性强,孔隙类型主要包括有机质孔隙和无机矿物孔隙。储层平均孔隙体积为0.27 cm^(3)/g,平均比表面积为8.7 m^(2)/g,宏孔提供了较大的孔隙体积,孔隙比表面积主要由介孔贡献,微孔对孔隙体积和比表面积的贡献较小。石英-长石碎屑以及白云石有利于孔缝的形成,而黏土矿物与方沸石等会堵塞储层的孔隙和裂缝,但是储层裂缝发育广泛,致密的混积岩矿物组分与孔隙参数相关性不太明显。研究区油层分布受优势岩性和储层物性控制,优质储层主要分布在孔隙度和渗透率相对较高的中深层,平均孔喉半径在0.05~0.15μm之间,中值压力(Pc50)较低,孔喉连通性较好,有利于页岩油的渗流。
This study investigates the pore structure characteristics and formation mechanisms of high-quality hybrid shale oil reservoirs in the fourth member of the Paleogene Shahejie Formation(Es⁴)within the western sag of the Liaohe Depression.A suite of advanced analytical techniques was employed,including argon ion polishing-field emission scanning electron microscopy(FE-SEM),CO₂adsorption,low-temperature N₂adsorp⁃tion,and high-pressure mercury intrusion(HPMI).Results show that the shale oil reservoirs in the study area exhibit complex lithof acies and strong heterogeneity.The dominant pore types include organic matter pores and inorganic mineral pores.The average pore volume is 0.27 cm^(3)/g,and the average specific surface area is 8.7 m^(2)/g.Macropores contribute most to the pore volume,mesopores dominate the specific surface area,while micropores have a limited impact on both.Quartz-feldspar clasts and dolomite promote the development of inter⁃granular pores and microf ractures,whereas clay minerals and analcime tend to block pore throats and fractures.However,the widespread development of natural fractures in the reservoir mitigates this effect.The correlation between mineralogical composition and pore structure parameters is relatively weak in these tight hybrid lithof a⁃cies.The distribution of oil layers in the study area is controlled by favorable lithologies and reservoir physical properties.High-quality reservoirs are mainly found in the middle-deep zones with relatively high porosity and permeability,where the average pore-throat radius ranges from 0.05 to 0.15μm,the median pressure(Pc50)is low,and the pore-throat connectivity is good,all of which facilitate the flow of shale oil.
作者
姚睿
李渔刚
唐春燕
康武江
赵春翔
李长林
YAO Rui;LI Yugang;TANG Chunyan;KANG Wujiang;ZHAO Chunxiang;LI Changlin(Research Institute of Petroleum Exploration and Development,PetroChina Liaohe Oilfield Company,Panjin,Liaoning 124010,China;School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China)
出处
《现代地质》
2025年第6期1633-1647,共15页
Geoscience
基金
国家重大科技专项“致密油注气及多介质协同提高采收率新技术”(2025ZD1404405)。
关键词
辽河坳陷
古近系
沙河街组
混积型页岩油储层
孔隙结构
储层成因
Liaohe Depression
western sag
Shahejie Formation
hybrid shale oil reservoir
pore structure
reservoir formation mechanism
