松辽盆地古龙凹陷青一段细粒沉积岩旋回地层分析及沉积充填响应特征

Cyclic stratigraphy of fine-grained sedimentary rocks and sedimentary filling response characteristics of Member Qing-1 in Gulong Sag,Songliao Basin

细粒沉积岩特别是页岩因其具有巨大的油气资源潜力而成为备受各国重视的研究领域,已经成为世界能源领域的重要发展方向。细粒沉积岩粒度细小、微观构造复杂、沉积旋回界面识别困难,矿物组分变化及有机质富集的主控因素也不够清楚,严重制约了页岩油勘探的快速推进。旋回地层学通过岩性组合识别、频谱分析、小波分析、滤波和调谐等方法可识别米兰科维奇旋回信号,建立高精度旋回地层格架,是解决细粒沉积岩旋回界面识别的一种有效方法。综合利用岩心精描及分析化验资料,对松辽盆地北部古龙凹陷青一段开展以米兰科维奇理论为指导的天文旋回研究及沉积充填响应特征分析。研究结果表明,古龙凹陷青一段可划分为3个长偏心率旋回、10个短偏心率旋回和26个斜率旋回。整体上超长偏心率与古气候的周期性变化具有良好的对应性,长偏心率旋回与矿物组合、白云岩发育和有机碳富集具有良好的对应特征,短偏心率和斜率旋回与矿物组合、白云岩、有机碳的内幕变化期次具有明显的匹配关系。研究成果为湖相盆地内部非常规油气勘探提供了理论依据。

Fine-grained sedimentary rock,especially shale,has become an important research field in the world because of its huge potential of oil and gas resources.Fine-grained sedimentary rocks are characterized by fine grain size,complex microstructure,difficult identification of sedimentary cycle interface,unclear main controlling factors of mineral composition change and organic matter enrichment,which seriously restrict rapid progress of shale oil exploration.Cycle stratigraphy can identify Milankovitch cycle signals through lithologic combination identification,spectrum analysis,wavelet analysis,filtering and tuning,and establish high-accuracy cycle stratigraphic framework,which is an effective method to identify cycle interface of fine-grained sedimentary rocks.In this paper,astronomical cycle research and sedimentary filling response characteristics of Member Qing-1 in Gulong sag in northern Songliao Basin,guided by Milankovitch theory,are carried out by using detailed core description and analysis data.The results show 3 long eccentricity cycles,10 short eccentricity cycles and 26 slope cycles in Member Qing-1 in Gulong sag.Generally,super long eccentricity has a good correspondence with periodic change of paleoclimate,long eccentricity cycle has a good correspondence with mineral assemblage,dolomite development and organic carbon enrichment,and short eccentricity cycle and slope have a clear matching relationship with internal change periods of mineral assemblage,dolomite and organic carbon.The research results provide theoretical basis for unconventional oil and gas exploration in lacustrine basins.