致密油分布的沉积相控作用分析:以齐家地区高台子油层为例

为了找出齐家地区高台子油层致密油分布的控制因素,通过精细的沉积解剖特征研究,认为齐家地区高三、高四油层组沉积相为浅水三角洲相,由北向南依次发育三角洲平原-三角洲前缘-前三角洲亚相,基准面下降期间伴随多次小规模的湖进造成三角洲外前缘与前三角洲泥,三角洲内前缘前端与三角洲外前缘泥岩呈多期迭加分布,给源内致密油提供了源储匹配的前提。其次,分析了沉积相对致密储层、优质生油层及两者匹配关系这"三大条件"的控制作用,指出齐家地区存在两种致密油藏:三角洲内前缘前端远砂坝致密油藏和三角洲外前缘席状砂致密油藏。通过比较"三大条件"的优劣程度,认为前者储层条件、烃源岩条件及源储匹配较好,是本区最重要的致密油藏类型。最后指出齐家南部外前缘前端远砂坝微相是下一步致密油勘探的最有利微相。

Control function of sedimentary facies on tight oil distribution: taking Gaotaizi oil layer in Qijia area as an example

In order to find out the controlling factors of tight oil distribution in Gaotaizi oil layer of Qijia area， through the detailed study of sedimentary characteristics，the authors consider that the sediment facies is shallow delta in G3 － G4 oil layers， and developing delta plain， delta front and prodelta subfacies from north to south． Mul- tiple and small scale transgressions during the base level falling cause the multistage superposition between delta outer front and prodelta mud，and between the terminal of delta inner front and the mud of delta outer front，which provide the premise of source and storage match for inner source tight oil． Also，the authors analyze the control ac- tion of sediment facies on tight reservoir，high quality oil layers and the matching relationship between them，and point that there exist two kinds of tight oil reservoir in Qijia area，tight reservoir of distal bar in the terminal of delta inner front，tight reservoir of sheet sand in delta outer front． By comparing the superiority of the three conditions， the former is better in reservoir condition，hydrocarbon source rock condition and source storage matching，and is the most important tight oil reservoir type． Finally，it is pointed out the tight reservoir of distal bar in terminal of delta outer front is the most favorable microfacies in the next tight oil exploration in southern Qijia area．