黔东南麻江-凯里地区志留系油砂矿储层特征

Reservoir Characteristics of Silurian Oil Sands in Majiang-Kaili Area,Southeastern Guizhou Province

贵州东南部麻江-凯里地区油砂资源丰富,构造上处于上扬子地台黔南坳陷东部,东邻雪峰山推覆体,北西与黔中隆起及武陵坳陷相接。通过野外露头和浅井岩心观察,运用铸体薄片鉴定、物性分析及含油率测试等手段,对该地区志留系翁项群油砂储层特征及含油性特征进行了研究。结果表明:研究区油砂主要发育在翁项群二段和三段中,含油砂岩成分成熟度和结构成熟度中等一好,岩性均以中—细粒(含)钙质、硅质岩屑石英砂岩和石英砂岩为主;凯里地区含油砂岩胶结物含量在8%~23%之间,以亮晶方解石为主,局部连晶,硅质胶结物含量在1%~10%之间,以石英次生加大边产出,而麻江地区含油砂岩胶结物含量仅为1%~7%,以硅质胶结物为主;研究区砂岩发育有原生粒间孔、粒间溶孔、粒内溶孔、铸模孔及裂缝等孔隙类型,以原生粒间孔为主,孔隙度介于0.3%~7.0%之间,渗透率介于0.006×10^(-3)~6.21×10~3μm^2之间,为低孔低渗储层,恢复含油率平均值为3.73%。结合以上测试手段和实验分析结果,判断凯里地区油砂含油性较麻江地区稍好。

Majiang-Kaili area in southeastern Guizhou Qiannan depression of upper Yangtze platform by the province has rich oil sands and locates in the eastern structure near snow mountain nappe in the east and with connection to the Qianzhong uplift and Wuling depression in north-west.Based on outcrop and shallow well core observation,reservoir characteristics and petroliferous characteristics of the oil sands in Wengxiang Group of Silurian in this area were studied by means of cast thin section observation ,porosity and permeabil- ity analysis and oil content test of the samples.The result shows that the oil sands mainly developed in the second and third members of the Wengxiang Group.The reservoir dominantly consists of medium-fine grained （including） calcareous or siliceous lithic quartz sandstone and quartz sandstone with moderate-high composi- tional and textural maturity.In Kaili area,oil-bearing sandstone cement content in oil sands was 8% to 23%, which is dominated by sparry calcite with few crystal stocks,and the siliceous cement content is 1% to 10% ,which was produced by secondary quartz enlarged pore-fringes;and in Majiang area,the oil-bearing sandstone cement content is only 1% to 7% ,which is dominated by silcous cement.Primary intergranular pore,intergranular dissolved pore,intraparticle dissolved pore,cast pore and fractures developed in the sand- stones of the research area.The main pore type of the reservoir is the primary intergranular pore with porosi- ty between 0.3% and 7% and permeability between 0.006×10-3μm2 and 6.21×10-3μm2.So the sandstone reservoirs were classified as low-porosity and low-permeability ones.Although the corrected average oil content was 3.73%,the oil content of the sandstones in Kaili area was higher than that in Majiang area combined with the above test and the experimental analysis results.