庆城地区长8致密砂岩储层含油性影响因素分析

doi:10.3969/j.issn.1006-6535.2026.01.005

摘要/Abstract

摘要： 针对庆城地区长8储层含油性差异较大、油层分布控制因素不明确的问题,综合钻井、测井数据及实验分析数据,运用孔隙度反演法、孔喉恢复法、地质因素叠合法,开展了沉积微相、储层孔喉特征、构造及盖层条件与含油性关系的研究。结果表明:研究区长8砂岩储层发育三角洲前缘水下分流河道、河口砂坝、水下分流河道侧缘沉积微相,其中,水下分流河道单砂体厚度为2~15 m,大孔喉发育,且孔喉分布集中,最有利于油气的储集;河口砂坝的单砂体厚度为2~8 m,孔喉分布较集中;水下分流河道侧缘单砂体厚度为2~3 m,孔喉偏细,其物性和含油性较前两者差。早白垩世末期,油气大规模运聚时,研究区长8储层的可动流体饱和度较高,多在70%以上,有利于油气充注。成岩晚期河道侧缘砂体进一步压实,胶结作用较强,导致其孔喉变细,可动流体饱和度降低。长8油藏形成之后可能发生过油气调整,油层的分布受鼻状构造控制不明显,而与断裂带分布关系密切,当上覆泥岩隔层厚度大于10 m时,油气易富集。该研究可为庆城地区地质“甜点”区优选提供理论依据,对类似地区的油气成藏规律研究具有一定借鉴意义。

关键词: 致密砂岩, 长8储层, 含油性, 庆城地区, 成岩作用, 鄂尔多斯盆地西南部

Abstract: To address the big difference in sandstone oil-bearing property in Chang 8 of Qingcheng Area and the unclear controls on oil layer distribution,drilling,logging and experimental data were integrated by using porosity inversion,pore-throat restoration,overlays of geological factors,investigations were conducted on the relationships with oil bearing property concerning sedimentary microfacies,pore throat characteristics,structure and caprock conditions.The results show that the Chang 8 sandstones in the study area were deposited in delta-front environments,including three microfacies:underwater distributary channels, mouth bars and lateral splays of underwater distributary channels.Among them,the single sand bodies in the underwater channel facies ranged between 2~15 m in thickness,with well-developed coarse pore throats that were tightly clustered-these facies were most favorable for hydrocarbon accumulation.The mouth bar facies had single sand bodies between 2~8 m in thickness with relatively concentrated pore throat sizes.The channel-splay facies had thinner(2~3 m)sand bodies with finer pore throats;their reservoir quality and oil-bearing property were poorer than the other two facies.The late Early Cretaceous experienced large-scale hydrocarbon migration and accumulation, and the movable-fluid saturation of the Chang 8 reservoir was generally high(mostly above 70%),which is favorable for hydrocarbon charging.In late diagenesis,the channel splay sand bodies were further compacted and strongly cemented,which resulted in finer pore throats and reduced movable-fluid saturation.After the reservoir formation,there were possible redistribution of hydrocarbons for the oil layer distribution was not closely controlled by anticlines but was strongly associated with fault zones.Hydrocarbon accumulation tended to be enhanced where the overlying mudstone seal exceeded 10 m in thickness.This study provides a theoretical basis for identifying geological "sweet spots" in Qingcheng Area and offers insights for understanding hydrocarbon accumulation in analogous areas.

Key words: tight sandstone, Chang 8 Reservoir, oil bearing property, Qingcheng Area, diagenesis, southwestern Ordos Basin

中图分类号:

TE122.2

王国熙, 钟红利, 蔡永吉, 李海龙, 刘美荣. 庆城地区长8致密砂岩储层含油性影响因素分析[J]. 特种油气藏, 2026, 33(1): 43-51.

WANG Guoxi, ZHONG Hongli, CAI Yongji, LI Hailong, LIU Meirong. Factors influencing tight sandstone oil bearing property in Chang 8 of Qingcheng Area[J]. Special Oil & Gas Reservoirs, 2026, 33(1): 43-51.

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