石油实验地质2025，Vol.47Issue(5)：1049-1062,14.DOI:10.11781/sysydz2025051049
鄂尔多斯盆地奥陶系盐下深层马二、马三段成藏地质特征及有利勘探方向
Geological characteristics of accumulation and favorable exploration directions of the second and third members in Ordovician Majiagou Formation of deep subsalt layers,Ordos Basin
摘要
Abstract
The geological conditions for natural gas accumulation in the deep subsalt layers of the second and third members of the Ordovician Majiagou Formation(Ma 2 and Ma 3)in the Ordos Basin are complex,and favorable exploration directions in this area remain unclear.These disadvantages result in a lack of major break-throughs in subsalt exploration.To clarify the geological characteristics of deep subsalt natural gas accumulation and to identify new exploration potential zones,a systematic analysis of the geological conditions was conducted using drilling,seismic,logging,and analytical testing data.The geological causes for poor gas testing performance in subsalt layers were revealed,and favorable exploration directions and accumulation models for deep subsalt natural gas were proposed.The results indicated that source rocks,reservoirs,and faults were the main factors controlling the distribution of deep subsalt natural gas.The Ma 2 and Ma 3 members in the deep subsalt layers exhibited spatial differences in hydrocarbon supply characteristics.In the eastern part of the basin,the hydrocarbon supply was mainly derived from Lower Paleozoic marine oil-type gas,with a relatively higher carbon isotope value in methane(-41.6‰).In the central part of the basin,the supply was a mixture of Lower Paleozoic marine oil-type gas and Upper Paleozoic coal-derived gas,with moderate amounts of carbon isotope in methane(-35.9‰).On the eastern side of the central paleo-uplift,the basin could be further divided into the northwestern and south-western parts.In the northwestern part,the hydrocarbon supply was a mixture of Lower Paleozoic oil-type gas and Upper Paleozoic coal-derived gas,with an intermediate carbon isotope value in methane(-38.7‰).In the southwestern part,the supply was primarily from Upper Paleozoic coal-derived gas,with a significantly higher carbon isotope value in methane(-32.2‰).The deep subsalt reservoirs are diverse in types,mainly controlled by paleo-geomorphology and sedimentary facies zones,with evident zoning characteristics.High-quality reservoirs mainly develop gypsum mold pores,caves,and shoal pores.The role of faults in facilitating the migration and conduction of subsalt natural gas is relatively limited.The widely developed gypsum salt layers in Ma 2 and Ma 3 members exhibit strong plasticity and are prone to deformation,which to some extent obstructed and reduced the vertical and lateral migration capacity of natural gas.This resulted in the overall low abundance of deep subsalt natural gas.Based on the comprehensive analysis,three favorable exploration directions were proposed:lateral hydrocarbon supply on the eastern side of the central paleo-uplift,self-generated and self-stored reservoirs in the eastern basin,and effective source,reservoir and fault matching zones in the central basin.Corresponding accu-mulation models were established.关键词
盐下深层/成藏地质特征/勘探方向/奥陶系/鄂尔多斯盆地Key words
deep subsalt layer/geological characteristics of accumulation/exploration direction/Ordovician/Ordos Basin分类
能源科技引用本文复制引用
陈朝兵,段晨阳,严锐锋,高建荣,白莹,张延兵,徐旺林,张月巧..鄂尔多斯盆地奥陶系盐下深层马二、马三段成藏地质特征及有利勘探方向[J].石油实验地质,2025,47(5):1049-1062,14.基金项目
深地国家科技重大专项(2025ZD1010507)、国家科技重大专项(2011ZX05044)和陕西省自然科学基础研究计划(2024JC-YBMS-227)联合资助. （2025ZD1010507）
