细粒岩天文旋回识别及在精细地层划分上的应用-以辽河西部凹陷雷家地区沙四段为例
- 收稿日期:
2023-06-26
- 网络出版日期:
2024-01-08
摘要: 【目的】渤海湾盆地辽河坳陷西部凹陷雷家地区沙四段发育以粘土、长英质、碳酸盐及方沸石矿物混合的湖相细粒沉积岩，为该区油气赋存的主要载体，由于混合细粒岩成分复杂且横向变化快，导致储层非均质性强，为优质储层预测带来一定困难。【方法】以西部凹陷雷家地区雷15井、雷14井和雷61井为例，基于时间序列分析方法、高精度碳酸盐U-Pb定年及自然伽马测井数据对沙四段混合细粒岩进行旋回地层学分析。【结果】1）以相关系数法估算雷15井、雷14井和雷61井的最佳沉积速率，发现最佳沉积速率依次增大，分别为10.57 cm/kyr、11.4 cm/kyr和13.93 cm/kyr；2）对古气候替代指标（自然伽马）进行频谱分析，与标准ETP曲线（偏心率、斜率、岁差合成曲线）数据频谱分析结果进行对比，识别雷15井、雷14井和雷61井混合细粒岩中的天文旋回信号，并利用405 kyr长偏心率进行天文调谐，以雷14井2766.61m处年龄43.4±1.7 Ma为锚点，建立绝对天文年代标尺；3）沙四段中识别出6个405 kyr长偏心率周期，~17个~129 kyr短偏心率周期，结合地球轨道周期与高频层序之间的联系，建立偏心率尺度的精细地层划分对比格架。【结论】通过对雷家地区沙四段开展旋回地层学研究，有效识别沙四段中天文旋回信号，以量化方式建立具备时间属性的精细地层划分对比格架，对该区油气进一步勘探具重要指导作用，并且拓宽旋回地层学在渤海湾盆地的适用性。
Identification of astronomical cycles in mixed fine-grained sedimentary rocks and its application in fine stratigraphic division and correlation - a case study of the fourth member of Shahejie Formation in the Leijia area, the western sag of the Liaohe Depression
- Received Date:
2023-06-26
- Available Online:
2024-01-08
Abstract: [Objective]The lacustrine fine-grained sedimentary rock mixed with clay, felsic, carbonate and analcite minerals develops in the fourth member of Shahejie Formation of the Leijia area in the western sag of the Liaohe Depression in the Bohai Bay Basin and is the main carrier for the occurrence of oil and gas. Due to the complex composition and rapid lateral changes of mixed fine-grained rocks, the reservoirs are highly heterogeneous, which brings certain difficulties to the prediction of high-quality reservoirs. [Methods] Taking the Lei 15 well, the Lei 14 well and the Lei 61 well in the Leijia area of the western sag as an example, based on time series analysis method, high-precision carbonate U-Pb dating and natural gamma logging data, the mixed fine-grained rocks of the the fourth member of Shahejie Formation were analyzed by cyclostratigraphy. [Results and Discussions] 1) The optimal sedimentation rates of Well Lei 15, Well Lei 14 and Well Lei 61 were estimated by COCO, and it was found that the optimal sedimentation rates increased sequentially and were 10.57 cm/kyr, 11.4 cm/kyr and 13.93 cm respectively; Perform spectrum analysis on the paleoclimate proxy indicator (GR) and compare it with the data spectrum analysis results of the standard ETP curve (eccentricity, slope, precession composite curve), identify astronomical cycle signals in mixed fine-grained rocks in Wells Lei 15, Lei 14 and Lei 61, And use the 405 kyr long eccentricity for astronomical tuning, and use the age 43.4±1.7 Ma at 2766.61m in Well Lei 14 as the anchor point to establish an absolute astronomical time scale. [Conclusions] By conducting cyclostratigraphic research on the fourth member of Shahejie Formation in the Leijia area, astronomical cycle signals in the fourth member of Shahejie Formation can be effectively identified. This method quantitatively establishes a fine stratigraphic division and comparison framework with time attributes, which plays an important role in guiding further oil and gas exploration in the area and broadens the applicability of cycle stratigraphy in the Bohai Bay Basin.
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