海相油气地质2025，Vol.30Issue(1)：41-58,18.DOI:10.3969/j.issn.1672-9854.2025.01.004
伊拉克东南部白垩系塞诺曼阶—下土伦阶生物碎屑灰岩层序研究进展
Research progress on the bioclastic limestone sequence of Cretaceous Cenomanian-Lower Turonian in southeastern Iraq
摘要
Abstract
The Cenomanian-Lower Turonian in southeastern Iraq is characterized by thick bioclastic limestone,with complex stratigraphic structure and nested sequences of different levels.The sequence recognition is important for stratigraphic division and reservoir correlation.Thick bioclastic limestone reservoir is commonly developed by separated waterflooding,and the study of sequences can lay a geological foundation for the division of development units.Taking six giant oilfields as example,all of which developed thick bioclastic limestone as main pay formations in the Cenomanian-Lower Turonian,the sequence schemes of Cenomanian-Lower Turonian are summarized.This paper adopts the scheme of dividing the Cenomanian-Lower Turonian into four of a third-order sequence corresponding to the four maximum flooding surface(K120,K130,K135,and K140).Mechanisms and characteristics of key sequence boundary such as unconformities,leaching and dissolution,thin carbonaceous mudstone,facies transition,facies mutation,maximum flooding surface,and hardground are summarized.Southeastern Iraq is located in the northeastern margin of the Arabian Plate,and during the Cenomanian-Early Turonian it is in a stable passive continental margin environment.This paper uses the quadratic model of classical stratigraphy to study the sequences of thick bioclastic limestone.According to the sequence theory,the sequence model of slightly rimmed carbonate ramp is established based on the depositional setting of Cenomanian-Lower Turonian.Different paleogeographic locations have different water depths during the process of sea-level rise and fall,so carbonate deposition rates and petrological features have different sensitivities to sea-level changes at different location.The water background and paleogeography control the sedimentation of different oilfields in southeastern Iraq.The sequence and depositional evolution are therefore revealed.Through elucidating the mechanism of sequence,and the effects of sequence order and sequence boundary on bioclastic limestone reservoirs are clarified.The effects of sea-level fall magnitude,exposure span and climate on formation structure,lithology and physical properties are illustrated.Typically,the high-order sequences boundary exposes for a long time,and the stratigraphy is weathered to a high degree.In arid climates,soilization and breccia collapse occur,and an unconformable surface can be formed,which is not conducive to improve the physical properties of the reservoir.In humid climates,large-scale leaching and dissolution occur,or thin carbonaceous mudstone can be formed locally.The exposure time of the low-order sequences boundary is short,and the leaching and dissolution occurs without destroying the strata structure,which can form high-quality reservoirs.Finally,problems and development trend in the sequence study of Cenomanian-Early Turonian in southeastern Iraq are pointed out,providing a reference for the separated waterflooding development of thick bioclastic limestone reservoir.关键词
生物碎屑灰岩/层序/沉积演化/层序控储/塞诺曼阶—下土伦阶/伊拉克东南部Key words
bioclastic limestone/sequence/sedimentary evolution/sequence control reservoir/Cenomanian-Lower Turonian/southeastern Iraq分类
石油、天然气工程引用本文复制引用
李峰峰,任立新,李蕾,万洋,陈昊卫..伊拉克东南部白垩系塞诺曼阶—下土伦阶生物碎屑灰岩层序研究进展[J].海相油气地质,2025,30(1):41-58,18.基金项目
本文受中国石油科技重大专项课题"巨厚碳酸盐岩油藏注水开发关键技术研究与应用"(编号:2023ZZ19-01)和"ALBION碳酸盐岩储层联合研究"(编号:2021DQ0407)联合资助 （编号:2023ZZ19-01）
