东营凹陷细粒混积岩发育环境及其岩相组合:以沙四上亚段泥页岩细粒沉积为例

为了进行陆相断陷湖盆泥页岩细粒混积岩有利岩相预测，以指导页岩油气有利目标优选，综合运用岩心、薄片、全岩衍射、元素、古生物等资料，系统进行了东营凹陷沙四上亚段泥页岩细粒混积岩沉积环境恢复、岩相精细表征，揭示了沉积环境对岩相及其组合、分布的控制作用.研究表明，东营凹陷沙四上亚段泥页岩细粒混积岩沉积期整体上表现为气候由半湿润向湿润转化，自下而上显示碎屑物源输入量在增加、水体水深加大、盐度降低、还原性减弱的过程；有序复杂多变的沉积环境一定程度上控制了泥页岩细粒混积岩沉积组构复杂性，进而控制了细粒混积岩相的多样性、组合和分布规律性.建立基于“岩石组分、沉积构造、灰质结构和有机质丰度”四端元划分方案，将东营凹陷沙四上亚段泥页岩细粒混积岩划分为20类，实现了复杂细粒混积岩岩相划分；半湿润少物源条件下，浅湖强还原盐水环境主要发育膏盐、含有机质层状膏质泥岩和含有机质层状泥质灰（云）岩相组合，半深湖强还原咸水环境主要发育富有机质纹层状微晶泥质灰岩和富有机质纹层状灰质泥岩频繁互层岩相组合，半深湖强还原半咸水环境主要发育富有机质水平泥晶纹层泥质灰岩和富有机质纹层灰质泥岩频繁互层岩相组合，深湖还原半咸水环境主要发育富有机质层状泥质灰岩夹富有机质层状灰质泥岩相组合；湿润多物源条件下，深湖强还原半咸水环境主要发育富有机质层状泥质灰岩和富有机质层状灰质泥岩频繁互层岩相组合，深湖还原半咸水环境主要发育富有机质层状灰质泥岩夹富有机质层状泥质灰岩相组合. 

Sedimentary Environment and Lithofacies of Fine-Grained Hybrid Sedimentary in Dongying Sag: A Case of Fine-Grained Sedimentary System of the Es4

In order to predict the favorable lithofacies of shale fine-grained migmatite in the continental fault depressed lake basin and guide the optimization of shale oil and gas favorable targets, the sedimentary environment restoration and fine lithofacies characterization of shale fine-grained migmatite in the upper part of Es₄ Formation in Dongying sag are systematically carried out by using the data of core, thin section, whole rock diffraction, element and paleontology, etc., revealing the sedimentary environment and its combination and division to the lithofacies. The results show that the depositional period of shale fine-grained migmatites in the upper part of Es₄ Formation in Dongying depression is generally characterized by the transformation of climate from semi humid to humid, from bottom to top, it shows the process of increasing injection amount of clastic material source, increasing water depth, decreasing salinity and decreasing reducibility; the orderly and complex sedimentary environment controls the complexity of sedimentary fabric of shale fine-grained mixed rock to a certain extent, and then controls the diversity, combination and distribution regularity of fine-grained mixed rock facies. Based on the 4-terminal element division scheme of rock composition, sedimentary structure, calcareous structure and organic matter abundance, the shale fine-grained migmatites in the upper Es₄ of Dongying depression are divided into 20 types, and the complex fine-grained migmatites are divided into different lithofacies. Under the condition of semi humid with less material source, the shallow lake strong reducing salt water environment mainly developed gypsum salt, organic laminated gypsum mudstone combined with organic laminated argillaceous limestone (dolomite) facies, while the semi deep lake strong reducing salt water environment mainly developed organic laminated microcrystalline argillaceous limestone combined with organic laminated lime mudstone frequent interbedded lithofacies. In the strong reducing and brackish water environment of the semi deep lake, there are frequent interbedded lithofacies combined with organic rich horizontal micrite and organic rich laminated limestone mudstone, while in the reducing and brackish water environment of the deep lake, there are mainly organic bedded argillaceous limestone with organic rich bedded calcareous mudstone lithofacies combination. Under the condition of moist and multi-source, the deep lake strong reducing brackish water environment mainly develops the frequent interbedded lithofacies combined with organic rich layered argillaceous limestone and organic rich layered calcareous mudstone, while the deep lake reducing brackish water environment mainly develops the organic rich layered calcareous mudstone mingled with organic rich layered argillaceous limestone lithofacies association.