鄂尔多斯盆地西北部奥陶系马五5亚段颗粒白云岩特征及成因  

Origin and characteristics of grain dolomite of Ordovician Ma55 Member in the northwest of Ordos Basin, NW China

作　　者：张喜[1] 张廷山[1] 雷卞军[1] 张婧璇 张吉[3] 赵忠军[3] 雍锦杰 ZHANG Xi;ZHANG Tingshan;LEI Bianjun;ZHANG Jingxuan;ZHANG Ji;ZHAO Zhongjun;YONG Jinjie(School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500,China;Royal Melbourne Institute of Technology University,Melbourne,VIC 3001,Australia;PetroChina Changqing Oilfield Company,Xi’an 710018,China)

机构地区：[1]西南石油大学地球科学与技术学院,成都610500 [2]Royal Melbourne Institute of Technology University,Melbourne VIC3001,Australia [3]中国石油长庆油田公司,西安710018

出　　处：《石油勘探与开发》2019年第6期1115-1127,共13页Petroleum Exploration and Development

基　　金：国家科技重大专项“鄂尔多斯盆地大型低渗透岩性地层油气藏开发示范工程”(2016ZX05050)

摘　　要：基于钻井取心样品,通过岩石矿物学、地球化学等方法,探讨鄂尔多斯盆地西北部奥陶系马家沟组马五5亚段颗粒白云岩特征及成因。运用岩心、岩石薄片及扫描电镜观察、阴极发光特征分析、X-射线衍射分析、显微取样微量元素分析、激光取样δ^18O和δ^13C分析及包裹体均一温度等手段分析,证实颗粒白云岩是球状颗粒中的泥—粉晶白云石再结晶的产物,而不是颗粒灰岩白云化所致。在球状颗粒中,残留有与围岩泥晶白云岩中同样的石膏、石盐晶模;球状颗粒的组分(泥—粉晶白云石)与泥晶白云岩(泥晶白云石)微量元素特征、δ^18O、δ^13C值特征相近;颗粒白云岩球状颗粒之间的细—中晶白云石的Mn/Sr值约为5~8,而灰岩中的方解石、泥晶白云岩中的泥晶白云石、颗粒白云岩球状颗粒中的泥—粉晶白云石的Mn/Sr值约为0~2,表明颗粒白云岩经历强烈的成岩改造,包裹体均一温度(颗粒白云岩中细—中晶白云石约148.19℃、球状颗粒中的泥—粉晶白云石约122.60℃),进一步佐证颗粒白云岩经历埋藏成岩作用改造、δ^18O和δ^13C值负偏移的变化,颗粒白云岩球状颗粒中泥—粉晶白云石的δ^18O和δ^13C值符合负偏移而灰岩中方解石不符合。此外,指出阐明颗粒白云岩“云质再结晶”成因对该类白云岩储集层的预测有重要意义。The origin of grain dolomite in M55 Member of Ordovician Majiagou Formation in northwestern Ordos Basin was studied by geochemical and petrological tests on core samples.Observation of cores,thin sections and casting thin sections,analysis of cathodoluminescence,X-ray diffraction,microscopic sampling of trace elements,laser sampling δ^18O and δ^13C,and fluid inclusion homogenization temperature were conducted.The results show that the dolomite is the product of recrystallization of micritic to crystal powder dolomite rather than the product of dolomitization of grain limestone.In the spherical grains are residual gypsum and halite pseudo crystals identical with those in the host micritic dolomite.The spherical particles of dolomite has similar trace elements and δ^18O and δ^13C characteristics to micritic dolomite.Furthermore,Mn/Sr ratio of the fine medium dolomite between the dolomite grains is about 5-8,while Mn/Sr ratios of calcite in limestone,micritic dolostone in micritic dolomite,and micritic and powdery dolomite are about 0-2,indicating that the dolomite experienced strong diagenesis.Homogenization temperature of inclusions of fine medium dolomite is about 148.19℃,higher than that of inclusions in micritic to crystal powder dolomite(about 122.60℃),which also supports the conclusion that the grain dolomite experienced burial diagenesis and negative shift of δ^18O and δ^13C.The δ^18O,δ^13C values of micritic to crystal powder dolomite match with the negative migration,but those of calcite in limestone don’t.It is of great significance to elucidate the genesis of“dolomite recrystallization”for the prediction of such dolomite reservoirs.

关 键 词：鄂尔多斯盆地 奥陶系马家沟组 微量元素 δ13C Δ18O 包裹体 成岩作用 颗粒白云岩 白云岩成因 

分 类 号：TE122.1[石油与天然气工程—油气勘探]