北部湾盆地福山凹陷流沙港组致密油成藏条件及主控因素

查明北部湾盆地福山凹陷流沙港组致密油成藏条件并分析其控制因素，对于进一步明确致密油分布、厘定有利探区具有重要的指导意义。基于地震、录井、测井、岩心及分析化验等资料的综合分析，对北部湾盆地福山凹陷流沙港组有效烃源岩、有利储层、源储匹配关系等进行了研究。结果表明，流沙港组在最大湖泛期于皇桐和白莲两次凹内形成优质烃源岩，具有有机质丰度高、热演化程度适中的特点，提供了致密油形成的物质基础；受多物源供给影响，致密砂岩深入两次凹内，具有源储叠置、分布广泛的特点，溶蚀孔隙与构造裂缝发育，有利于致密油的近源运移与富集；主要烃源岩进入生油高峰期时凹陷构造已基本定型，无大型断裂发育，相对稳定的构造条件有利于致密油形成和保存。因此，福山凹陷流沙港组具备致密油成藏的有利条件，致密油纵向上主要分布在流一下亚段和流二段，平面上主要分布在皇桐次凹和白莲次凹，其形成和分布主要受控于优质烃源岩展布、富溶蚀孔隙"甜点"储层分布及有利的源-储叠置组合。 

Geological conditions and the main controlling factors for the tight oil accumulation in Liushagang Formation of Fushan Depression,Beibuwan Basin

Unravelling the accumulation conditions and their controlling factors for the tight oil in the Liushagang Formation, Fushan Depression, Beibuwan Basin, is critical for the further evaluation of the tight oil distribution and the favorable exploration area.Based on comprehensive analysis of seismic, well logging, core and lab tests in this study, the effective source rocks, favorable reservoir, and the source-reservoir matching relations were investigated.It can be proposed that the high-quality source rocks were formed in Huangtong, Bailian two sub-sags during the maximum lake flooding periods in Liushagang depositional stage and were characterized as high organic content and moderate degree of thermal evolution, and thus they provide the material basis for the formation of tight oil; due to the influence of multi-source supply, tight sandstones penetrated into these two sub-sags and they were widely distributed with superimposed source-reservoir assemblages. The development of dissolution pores and structural fractures was favorable for the migration and enrichment of tight oil; the tectonic conditions of the sag were relatively stable and no major fault system was active when the main sources entered peak oil window, and thus the relatively stable tectonic environment enabled the formation and preservation of tight oil accumulations.Therefore, the Liushagang Formation of the Fushan Depression have favorable geological conditions for the formation of tight oil, which mainly distribute in the lower L1 submember and L2 member vertically and Huangtong and Bailian sub-sags horizontally.The distribution of high-quality source rocks, the distribution of "sweet point" reservoirs being rich in dissolution pores and favorable superimposed source-reservoir assemblages are the three main controlling factors for the formation and distribution of tight oil in Liushagang Formation of Fushan Depression, Beibuwan Basin.