石油与天然气地质2025，Vol.46Issue(5)：1392-1409,18.DOI:10.11743/ogg20250502
鄂尔多斯盆地定边—富县地区延长组长8油层组致密油富集因素与富集模式
Enrichment factors and patterns of tight oil in the 8th oil group of the Yanchang Formation,Dingbian-Fuxian area,Ordos Basin
摘要
Abstract
Research on tight oil enrichment patterns under the condition of multi-source hydrocarbon supply is a key component of hydrocarbon enrichment theory.This study examines tight oil reservoirs in the 8th oil group of the Yanchang Formation(also referred to as the Chang 8 oil group)in the Dingbian-Fuxian area,Ordos Basin.By integrating data from drilling,well logging,core observations,thin-section observations,geochemical analysis,well tests,and production tests,we systematically evaluate the hydrocarbon generation potential of source rocks including the Zhangjiatan shales of the Chang 7 oil group,Lijiapan shales of the Chang 9 oil group,and the shales of the Chang 8 oil group.Accordingly,the general characteristics of tight oil reservoirs are clarified,the factors for tight oil enrichment in different oil plays are discussed,and thereby corresponding tight oil enrichment patterns are built.The results indicate that the Dingbian-Fuxian area contains three suites of good to excellent source rocks:the Chang 7,Chang 8,and Chang 9 oil groups.The widespread Zhangjiatan shales at the bottom of the Chang 7 oil group,among others,exhibit the greatest hydrocarbon generation potential,with an average total organic carbon(TOC)content of 6.1％.They are followed by the Lijiapan shales at the top of the Chang 9 oil group and shales in the Chang 8 oil group,which have average TOC contents of 5.3％and 3.9％,respectively and are distributed in the Ganquan-Fuxian-Zhidan area.Reservoirs in the Chang 8 oil group are dominated by fine-grained sandstones and siltstones,with measured peak porosity ranging from 4％to 12％(average:7.9％)and measured permeability from 0.10 × 10-3 μm2 to 0.40 × 10-3 μm2(median:0.26 × 10-3 μm2),establishing them as tight reservoirs.The tight-sandstone oil reservoirs in the area mostly show lenticular,zonal,and clustered distributions and are characterized by quasi-continuous accumulation.Shale tight oil enrichment in oil reservoirs in the 1st oil sub-group of the Chang 8 oil group(also referred to as the Chang 81 oil sub-group)is primarily controlled by the properties of the Chang 73 oil sub-group,including the hydrocarbon supply capacity of source rocks,the thickness of the thin mudstones between source rocks and reservoirs,and the sealing performance of the strong floor.In the Chang 81 oil sub-group,the single-source direct oil play in the Chang 73 oil sub-group,characterized by the configuration of upper source rocks and lower reservoirs,proves the most favorable,followed by the dual-source oil plays in the Chang 73 and 82 oil sub-groups,where reservoirs are sandwiched between source rocks.In contrast,the dual-source oil plays in the Chang 73 and 91 oil sub-groups,also characterized by reservoirs sandwiched between source rocks,represents the least favorable oil plays.Shale tight oil enrichment in the Chang 82 oil sub-group largely relies on the properties of the Chang 91 oil sub-group,including the hydrocarbon supply of source rocks,high-quality reservoir conditions,and the sealing performance of cap rocks.Within this oil sub-group,the single-source direct oil play in the Chang 91 oil sub-group,characterized by the configuration of upper reservoirs and lower source rocks,proves the most favorable.It is followed by the dual-source oil plays in the Chang 91 and 82 oil sub-groups,where reservoirs are again sandwiched between source rocks.Three distinct tight oil enrichment patterns are identified in the oil reservoirs of the Chang 8 oil group:(1)efficient enrichment pattern in the Chang 81 oil sub-group in the Dingbian-Wuqi area,driven by strong hydrocarbon supply from source rocks and high sealing performance;(2)complementary enrichment pattern in the Chang 82 oil sub-group in the Ganquan-Fuxian area,marked by the combination of excellent source rocks,high-quality reservoirs and cap rocks;and(3)synergistic enrichment pattern in the Chang 8 oil group in the Zhidan area,characterized by multiple hydrocarbon sources and high-quality reservoirs.This study aims to facilitate the efficient development and exploitation of tight oil in the Chang 8 oil group while advancing the tight oil enrichment theory.关键词
富集因素/富集模式/致密油/长8油层组/延长组/鄂尔多斯盆地Key words
enrichment factor/enrichment pattern/tight oil/Chang 8 oil group/Yanchang Formation/Ordos Basin分类
能源科技引用本文复制引用
吴伟涛,李天宇,闫新智,周凯,殷露,曹磊..鄂尔多斯盆地定边—富县地区延长组长8油层组致密油富集因素与富集模式[J].石油与天然气地质,2025,46(5):1392-1409,18.基金项目
延长油田股份有限公司科技攻关项目(YT11153FW0069). （YT11153FW0069）
