摘要
黔西南下石炭统打屋坝组发育了一套极具勘探潜力的页岩地层。目前,关于该套地层的层序划分方案和层序发育机制存在分歧,一定程度制约了该套优质页岩空间展布规律的认识。选取黔西南黔水地1井下石炭统打屋坝组(1457~2466 m)页岩为研究对象,以自然伽马测井曲线为替代指标,采用时间序列分析、合成预测误差滤波分析(INPEFA)和小波分析等方法,开展旋回地层学分析与层序地层学研究,旨在从天文旋回的角度,实现对该套页岩的层序地层“定量”划分。研究表明,黔西南下石炭统打屋坝组页岩地层记录了天文周期信号,相关系数法(COCO)估算显示其最优沉积速率为16.4 cm/ka,对应405 ka长偏心率周期的66.42 m沉积厚度。对黔水地1井GR分段(1457~1932 m和1932~2466 m)进行频谱分析和天文检验,上段和下段的最优沉积速率分别为16.5,11.2 cm/ka,打屋坝组一共记录了19个长偏心率周期,建立了“浮动”天文年代标尺,估算持续时限约7.86 Ma。通过沉积噪音模型(DYNOT和ρ1)恢复了相对海平面变化曲线。在旋回地层学研究建立的时间框架基础上,结合相对海平面极值、INPEFA和小波分析,识别了6个三级层序界面,划分出5个三级层序,并认为三级层序的发育受控于稳定的约1.2 Ma斜率振幅调制周期。应用旋回地层学开展了黔西南打屋坝组页岩地层的层序划分,探讨不同时间尺度下天文轨道参数与相对海平面变化的关系,实现了三级及四级层序地层的划分。该方法为海相页岩万年时间尺度的等时对比提供了可能,可为页岩油气勘探中优质烃源岩发育层段的预测提供精细的年代框架,进而为页岩油气勘探提供理论指导。
The Lower Carboniferous Dawuba Formation in Southwest Guizhou hosts a shale sequence with significant exploration potential.Current disagreements regarding its sequence division scheme and developmental mechanisms have somewhat hindered the understanding of the spatial distribution patterns of this high-quality shale.[Objective]Therefore,this study focuses on the Lower Carboniferous Dawuba Formation shale(interval 1457-2466 m)from the Well Qian Shui Di-1 in Southwest Guizhou.[Methods]Utilizing the natural gamma ray(GR)log as a proxy indicator,methods including time series analysis,INPEFA(integrated noise-enhanced population evolutionary frequency analysis),and wavelet analysis were applied to conduct cyclostratigraphic and sequence stratigraphic investigations.The aim is to achieve a"quantitative"division of the sequence stratigraphy for this shale unit from an astronomical forcing perspective.[Results]The results demonstrate that the Dawuba Formation shale records clear astronomical periodic signals.COCO(correlation coefficient)analysis estimates an optimal average sedimentation rate of 16.4 cm/ka,corresponding to a sediment thickness of 66.42 m for the 405 ka long eccentricity cycle.Spectral analysis and astronomical tuning were performed on segmented GR data from the Well Qian Shui Di-1(upper segment:1457-1932 m;lower segment:1932-2466 m).The optimal sedimentation rates for the upper and lower segments are 16.5 cm/ka and 11.2 cm/ka,respectively.The entire Dawuba Formation recorded 19 long eccentricity cycles,enabling the establishment of a"floating"astronomical time scale,which estimates a total duration of approximately 7.86 Ma for the formation.Furthermore,relative sea-level change curves were reconstructed using sedimentary noise modeling(DYNOT and ρ1 methods).Building upon the temporal framework established by cyclostratigraphy,and integrating relative sea-level extrema,INPEFA,and wavelet analysis results,six third-order sequence boundaries were identified,dividing the formation into five third-order sequences.The development of these third-order sequences is interpreted to be controlled by a stable approximately 1.2 Ma obliquity amplitude modulation cycle.[Conclusion]By applying cyclostratigraphy to the sequence division of the Dawuba Formation shale,this study explores the relationship between astronomical orbital parameters and relative sea-level change at different temporal scales,achieving the division of both third-order and fourth-order sequences.This methodology enables potential high-resolution(10000-year scale)chronostratigraphic correlation of marine shales.It provides a refined temporal framework for predicting intervals of high-quality source rock development within shale sequences,thereby offering crucial theoretical guidance for shale oil and gas exploration.
作者
王嘉伟
金思丁
魏祥峰
郝景宇
陈义才
李露艳
马超
WANG Jiawei;JIN Siding;WEI Xiangfeng;HAO Jingyu;CHEN Yicai;LI Luyan;MA Chao(College of Energy,Chengdu University of Technology,Chengdu 610059,China;National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China;SINOPEC Exploration Company,Chengdu 610041,China)
出处
《地质科技通报》
北大核心
2025年第4期288-303,共16页
Bulletin of Geological Science and Technology
基金
国家自然科学基金项目(42172137)。
关键词
旋回地层学
时间序列分析
层序地层学
海平面变化
斜率调幅
页岩
黔西南
cyclostratigraphy
time series analysis
sequence stratigraphy
sea-level change
obliquity amplitude modulation
shale
Southwest Guizhou
