松辽盆地北部扶余油层致密油成藏条件及甜点区优选

Geological condition and sweet area selection of Fuyu Formation in the north of Songliao Basin

松辽盆地北部扶余油层致密油是典型的源下致密油藏,具有形成大规模、连续型致密油藏的有利地质条件。通过对大量实验数据及钻井资料分析统计,对松辽盆地北部扶余油层致密油烃源岩条件、沉积环境、储层特征等成藏条件进行了综合分析,研究表明扶余油层致密油形成受成熟烃源岩与三角洲前缘相带控制,主要储集体为曲流河点坝砂体、分流河道砂体,具有单层厚度薄、横向变化快、垂向错叠连片的特点。储层主要以微米-纳米孔隙为主。常规储层和致密储层的分界为孔隙度为12%、渗透率为1×10^-3μm^2、孔喉半径为350nm,以孔隙度为8%、渗透率为0.1×1×10-3μm^2、孔喉半径为75nm为界将致密储层细分为Ⅰ类和Ⅱ类。扶余油层致密油藏主要成藏动力为青一段有效烃源岩的生烃增压作用,属于倒灌成藏机制,断裂是主要的运移通道,构造高部位是致密油富集场所。优质甜点区主要分布在大庆长垣、三肇凹陷中心部位,以及齐家古龙凹陷西侧。

The tight oil of Fuyu reservoir in northern Songliao Basin is a typical under-source tight reservoir,which has favorable geological conditions for forming large-scale and continuous tight reservoirs.Based on the analysis and statistics of a large number of experimental data and drilling data,the reservoir forming conditions of tight oil source rocks,sedimentary environment and reservoir characteristics of Fuyu reservoir in northern Songliao Basin are comprehensively analyzed.The study shows that the formation of tight oil in Fuyu reservoir is controlled by mature source rocks and delta front facies belt.The meandering river point bar sand body and distributary channel sand body have thin single layer thickness,fast lateral variation and vertical staggered links.Reservoirs are mainly micron-nano pore.The boundary between conventional reservoir and compact reservoir is 12% porosity,1×1×10-3μm2 permeability and 350 nm pore throat radius.The internal boundaries of compact reservoir are 8%porosity,0.1×1×10-3μm2 permeability and 75 nm pore throat radius.The main driving force of tight oil reservoir formation is hydrocarbon generation and pressurization of effective source rocks in the first member of Qinghai Formation,which belongs to the mechanism of inverted reservoir formation.Faults are the main migration pathway,and high-quality dessert areas are mainly distributed in the central part of Daqing Placanticline,Sanzhao Depression and west side of Qijia Gulong Depression.