东营凹陷永82井沙四段紫红色泥岩特征及其在层序划分中的应用  

Characteristics of red mudstone and its significance in recognition of sequence boundary of Es_4 in Dongying depression

作　　者：张立强[1] 杨晚 侯冠群[3] 

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249 [2]Missouri University of Science and Technology,Rolla Missouri 65409 [3]成都理工大学能源学院,四川成都610059

出　　处：《油气地质与采收率》2012年第5期43-46,53,共5页Petroleum Geology and Recovery Efficiency

基　　金：国家油气科技重大专项“东营凹陷北带中段深层沉积充填历史及砂岩富集带分布规律研究”(2011ZX05008-004-52)

摘　　要：在层序地层学研究中,层序界面的识别主要依据纵向分辨率较低的地震剖面、多解性较强的录井岩性组合和测井曲线等资料,而忽视了与不整合面有关的岩石古化学风化特征的分析,从而造成层序划分方案的多解性。通过对东营凹陷永82井沙四段紫红色泥岩的岩石学、地球化学以及古化学风化特征的分析,探讨了紫红色泥岩的纵向结构及其与层序界面的关系。永82井沙四段泥岩包括紫红色疏松状泥岩、紫红色致密块状泥岩、灰色层状泥岩以及灰色含膏泥岩和泥膏岩。沙四段紫红色疏松状泥岩具有强烈的擦痕面,其化学元素组成与古土壤相近,曾遭受程度较弱的古化学风化作用。结合紫红色泥岩的古化学风化特征认为,沙四段内部的层序界面与沙四段上、下亚段的边界不一致,紫红色疏松状泥岩段的顶界为沙四段内部的层序界面,而传统沙四段下亚段顶部的灰色砂岩夹紫色泥岩段属于上部层序的低水位体系域。In the study of sequence stratigraphy underground, the sequence boundary's identification is mainly based on the seismic section with low vertical resolution, log data with high multiple solution and so on, but ignoring rocks' paleo-weathering characteristic which is relative to unconformable surface. Therefore, it leads to the ambiguity of stratigraphic sequence correlation. Based on the study of petrology, geochemistry and paleo-weathering characteristics about the red mudstone in Es4 Yong 82 well of Dongyingdepression, red mudstone's vertical structure and the relationship with sequence boundary are discussed herein. The mudstone in Es4 of Yong 82 well mainly includes 4 types: red loose mudstone, red compact massive mudstone, dark grey banding mudstone and grey or grayish purple gypsum mudstone. The red loose mudstone has strong striated rock surface, and its chemical element combinations are close to paleosol. The mudstone's chemical index of alteration analysis indicates that the red loose mudstone has suffered low chemical paleo-weathering, its CIA tends to be lower from top to bottom, indicating rocks' chemical paleo-weathering tends to be lower when the depth increases. The top of the red loose mudstone is relative to the sequence boundary in Es4. However, the grey sandstone with red mudstone in the top of early Es4 should be attributed to upper sequence's low stand system.

关 键 词：沙河街组 泥岩 地球化学特征 层序边界 古土壤 东营凹陷 

分 类 号：TE122.1[石油与天然气工程—油气勘探]