塔河油田奥陶系古岩溶洞穴中分布有大量的充填砂岩,它们是极好的油气储集体.通过对塔河油田七区奥陶系古溶洞充填砂岩(以T615井岩心为主要剖析对象)的岩矿分析与对比、铸体薄片观察和测井资料分析,结合对盆地西北野外相似的奥陶系露头区的对比考察,查明了塔河油田奥陶系充填砂岩的成因与发育特征.认为该充填砂岩属于晚泥盆世东河塘期无障壁海岸砂充填奥陶系地下暗河溶洞所形成.充填砂岩的成分主要是亚岩屑砂岩和石英砂岩,砂岩物性好,原生粒间孔隙和溶蚀孔隙发育,表现出极佳的油气储集特性.在未来勘探开发中,应注重充填砂岩的沉积分布、溶洞的空间展布和前石炭纪古微地貌等方面的研究,为油田高效开发提供依据.

Ordovician karst-cave reservoirs develop in Tahe Oil Field, Tarim Basin. Sandstones filling in these Ordovician paleocaves are excellent oil reservoirs. Through the observation and analysis of cores and logging data from some wells in Tahe Block 7, especially for those of Well T615 as the typical research object, and associated with the investigation into the contrastable Ordovician outcrops far in the northwest of the basin, the development characteristics and genetic mechanism of filling sandstone in Ordovician paleocaves are ascertained in the oil field. The analysis result indicates that the sandstone filling in paleocaves was the no-barriering coast sand sediments that filled into the Ordovician karst caves along underground rivers the during Late Devonian Donghetang sedimentation. The filling sandstone consists of sublitharenite and quartzose sandstone. Contributing to good quartz sorting, high porosity and permeability, and developing primary intergranular pores and solution pores, the filling sandstone exhibits an excellent oil reservoir property. It is suggested that in the future exploration and development, it is necessary to carry out the researches including the sedimentary boundary of Late Devonian Donghetang filling sandstone in paleocaves, the spacial distribution of Ordovician karst caves and pre-Carboniferous micropaleogeomorphological feature.