四川盆地仪陇—平昌地区侏罗系凉高山组页岩油地质特征及富集条件

Geological characteristics and enrichment conditions of shale oil of Jurassic Lianggaoshan Formation in Yilong-Pingchang area,Sichuan Basin

基于钻井岩心的地球化学及其他实验分析结果,结合生产测试资料,对四川盆地仪陇—平昌地区侏罗系凉高山组页岩油地质特征及富集条件进行研究,并划分了勘探有利区。研究结果表明:(1)仪陇—平昌地区凉高山组为早侏罗世第3次湖盆扩张期的沉积产物,整体经历了凉下段滨湖—浅湖、凉上段中—下部深湖—半深湖及浅湖、凉上段上部三角洲前缘和浅湖的沉积环境变化。(2)研究区凉高山组页岩可分为长英质页岩、钙质页岩、黏土质页岩等3种;页岩有机质丰度高,TOC值为0.50%~3.39%,平均值为1.30%,有机质类型以Ⅱ_(1)和Ⅱ_(2)型为主,热演化程度高,镜质体反射率(Ro)为1.00%~1.90%,处于高—过成熟阶段。(3)凉高山组页岩物性较好,孔隙度为0.48%~7.17%,平均为3.61%,发育无机成因孔、有机孔和构造缝等储集空间类型;含油性较好,以轻质组分为主,整体呈零散状、点状分布,局部呈团块状富集;凉上段下部富有机质页岩更发育,是目前勘探的重点层位。(4)凉高山组页岩油气的富集受控于前陆盆地过渡期的弱沉降环境、大面积分布的深湖相沉积、较高的热演化程度以及普遍发育的微裂缝。中南部为页岩油气潜力区,页岩储层厚度一般大于15 m,TOC值大于1.50%,孔隙度大于4.00%,R_(o)大于1.30%;凉高山组页岩油资源量为26.75×10^(8)t、页岩气资源量为1.72×10^(12)m^(3),有望成为四川盆地石油产量增加的主力层系。

Based on the geochemical and other experimental analysis results of drilling cores,combined with production testing data,the geological characteristics and enrichment conditions of shale oil of Jurassic Lianggaoshan Formation in Yilong-Pingchang area of Sichuan Basin were studied,and favorable exploration areas were divided.The results show that:(1)The Lianggaoshan Formation in Yilong-Pingchang area is a sediment during the third lacustrine basin expansion stage of Jurassic,which has undergone the sedimentary environment changes of shore lake to shallow lake in the lower member of Lianggaoshan Formation,deep lake to semi-deep lake and shallow lake in the middle and lower part of the upper member of Lianggaoshan Formation,and delta front and shallow lake in upper part of the upper member of Lianggaoshan Formation.(2)The shales of Lianggaoshan Formation can be divided into felsic shales,calcareous shales and clay shales,with a high abundance of organic matter,TOC values ranging from 0.50%to 3.39%and an average of 1.30%.The organic matters are mainly typeⅡ_(1)and typeⅡ_(2),with a high degree of thermal evolution and vitrinite reflectance(Ro)ranging from 1.00%to 1.90%,and indicating a high mature to over mature stage.(3)The shales of Lianggaoshan Formation have good physical properties,and the reservoir space types such as inorganic pores,organic pores and structural fractures are developed.The porosity ranges from 0.48%to 7.17%,with an average value of 3.61%.The oil-bearing capacity is good and mainly composed of light components,which is scattered and punctate in the whole,and locally concentrated in clumps.The lower part of the upper member of Lianggaoshan Formation is more developed with organic-rich shale,which is the focus of exploration at present.(4)The weak subsidence environment during the transitional period of foreland basin,widespread distribution of deep lacustrine sediments,the high degree of thermal evolution and widespread development of micro-fractures are favorable for shale oil and gas enrichment in Lianggaoshan Formation.The central and southern regions of the study area are shale oil and gas potential zones,with shale reservoir thickness generally greater than 15 m,TOC value greater than 1.50%,porosity greater than 4.00%,Ro greater than 1.30%.Lianggaoshan Formation has 26.75×10^(8)t of shaleoilresources and 1.72×10^(12)m^(3)of shale gas resources,which is expected to become themain layer for increasing oil production in Sichuan Basin.