摘要
利用钻井岩心、测井、地震等资料开展烃源岩、储集层评价,并通过天然气同位素组成、天然气组分、流体包裹体分析,开展天然气成因识别等工作,研究鄂尔多斯盆地深层奥陶系下组合膏盐岩相关地层的天然气成藏条件。结果表明,①下组合天然气为来自海相烃源岩的高热演化干气,其天然气甲烷碳同位素组成偏轻、乙烷碳同位素组成偏重。天然气组分判识结果是原油裂解气。烃类流体与硫酸盐发生过硫酸盐热化学还原反应,依据是岩心中见到硫磺晶体,天然气中发现硫化氢,烃类及硫化氢流体包裹体广泛发育。②奥陶系下组合环绕盐洼带大面积发育泥质岩,累计厚度为20~80 m。有效烃源岩大多为富有机质纹层泥质岩或者藻团块、藻云岩,有机碳测试含量主体范围为0.1%~0.5%,平均值为0.31%,最高可达3.24%。有机酸盐恢复后平均有机碳含量可达0.58%,表明烃源岩具备较好供烃潜力。③沉积期古隆起控制储集层分布。中央古隆起东侧发育乌审旗—靖边继承性次级古隆起,神木—子洲附近发育厚层盐岩形成的低隆,均控制准同生颗粒滩白云岩储集层分布。膏盐岩咸化环境对储集层发育具有促进作用。下组合发育白云岩晶间孔型、溶蚀孔型和裂缝型3类储集层,其中晶间孔和溶蚀孔为主要储集空间。④下组合发育致密碳酸盐岩和膏盐岩两类盖层,分别控制形成两类生储盖组合。总体是海相源岩供烃、滩相灰云岩储集、小微断裂输导、构造-岩性圈闭聚集的成藏模式。⑤下组合马家沟组三段和四段是重要目的层,平面上乌审旗—靖边次级古隆起和神木—子洲低隆是白云岩与灰岩交互过渡带,隆起带东侧发育致密石灰岩,利于形成岩性上倾遮挡气藏,近期两口风险井钻探效果良好,表明两个隆起带是重要勘探方向。
Based on drilling cores,well loggings and seismic data,source rocks and reservoirs are evaluated;and the natural gas genesis is identified through the analysis of natural gas isotopes,components and fluid inclusions,to study the gas accumulation conditions of the gypsum salt rock related strata of the Ordovician lower assemblage in Ordos Basin.(1)The natural gas from Ordovician lower assemblage is high thermal evolution dry gas from marine source rock,characterized by relatively lightδ13C value of methane and heavyδ13C value of ethane.The natural gas is identified as gas cracking from crude oil according to component analysis.Thermochemical sulfate reduction(TSR)reaction has happened between the hydrocarbon fluid and sulfate as sulfur crystals are found in the cores,hydrogen sulfide is found in the natural gas,and hydrocarbon and hydrogen sulfide fluid inclusions are widespread in secondary minerals.(2)Around the gypsum-salt lows,argillaceous rocks are extensive in the Ordovician lower assemblage,reaching a cumulative thickness of 20-80 m.The effective source rocks include argillaceous rock rich in organic laminae,algal clump and algal dolomite.Analysis shows that the source rocks have a dominant TOC of 0.1%-0.5%,0.31%on average and 3.24%at maximum.The source rocks have an average TOC of 0.58%after recovered through organic acid salt method,indicating the source rocks have high hydrocarbon supply potential.(3)In the sedimentary period,the palaeo-uplift controlled the distribution of reservoirs.The inherited secondary palaeo-uplift in Wushenqi-Jingbian east of the central palaeo-uplift and the low uplift formed by thick salt rocks near Shenmu-Zizhou area controlled the distribution of penecontemporaneous grain shoal dolomite reservoirs.The salinization sedimentary environment of gypsum salt rock can promote the development of reservoir.There are three types of dolomite reservoirs,the one with intercrystalline pore,with dissolution pore,and with fracture;intercrystalline and dissolution pores are main reservoir s
作者
徐旺林
李建忠
刘新社
李宁熙
张才利
张月巧
付玲
白莹
黄正良
高建荣
孙远实
宋微
XU Wanglin;LI Jianzhong;LIU Xinshe;LI Ningxi;ZHANG Caili;ZHANG Yueqiao;FU Ling;BAI Ying;HUANG Zhengliang;GAO Jianrong;SUN Yuanshi;SONG Wei(PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China;PetroChina Changqing Oilfield Company,Xi’an 710018,China)
出处
《石油勘探与开发》
SCIE
EI
CAS
CSCD
北大核心
2021年第3期549-561,共13页
Petroleum Exploration and Development
基金
国家重点研发专项(2017YFC0603106)
国家油气科技重大专项(2016ZX05004-006)
中国石油勘探与生产分公司科技项目(kt20180401)。
关键词
鄂尔多斯盆地
奥陶系下组合
膏盐岩
海相烃源岩
白云岩储集层
天然气成藏
Ordos Basin
Ordovician lower assemblage
gypsum-salt rock
marine source rock
dolomite reservoir
natural gas accumulation
