论四川盆地下三叠统飞仙关组天然气勘探

Discussion on gas exploration of Feixianguan Formation in the Lower Triassic of Sichuan Basin

近10余年来,四川盆地东北部下三叠统飞仙关组天然气勘探取得了显著突破,发现了普光、罗家寨、渡口河和铁山等大型气田。天然气主要富集于广梁海槽两侧台地边缘鲕粒滩相区。由于鲕粒滩地势较高,受海盆震荡影响,鲕粒滩经常露出水面遭受淡水淋溶,经混合水白云岩化作用及其后的溶蚀作用,鲕粒滩成片变为鲕粒溶孔白云岩、鲕粒溶孔灰质白云岩或鲕粒溶孔白云质灰岩,平均孔隙度高达8.16%,平均渗透率为93.326×10-3μm2,成为四川盆地最好的储层。气藏多为岩性-构造复合气藏。利用鲕粒滩地震异常识别模式,在盆地东部已发现104个鲕粒滩地震异常,为进一步勘探提供了新的目标。

Some giant gas fields such as Puguang, Luojiazhai, Dukouhe and Tieshan gas fields have been discovered in Feixianguan Formation of the Lower Triassic in Sichuan Basin in recent decade years. Natural gas mainly accumulated in oolite beach sedimentary facies of carbonate platform edge around Guangliang trough in Sichuan Basin. The topography of oolite beach was high. The oolite beach was often uncovered and subjected to freshwater leaching due to sea basin vibration. The sheets of oolite were changed into the dolomite with dissolved pore of oolite,calcite dolomite with dissolved pore of oolite and dolomitic limestone with dissolved pore of oolite. These rocks in Sichuan Basin are the best reservoirs with the mean porosity of 8.16% and the mean permeability of 93. 326×10^-3 μm^2. The major gas reservoirs in Sichuan Basin were litho-structural combined reservoirs. There found 104 seismic anomalies of oolite beach in the eastern Sichuan Basin using the recognition mode of seismic anomaly of oolite beach. The new targets for future gas exploration in Sichuan Basin were provided.