基石宝寨地区大地电磁测深电阻率成像--四川盆地东部边缘油气藏的启示

Electrical resistivity imaging in Shibaozhai area using magnetotelluric sounding:Enlightenment of hydrocarbon reservoirs on the eastern edge of the Sichuan Basin

石宝寨位于中国西南地区四川盆地,近年来,在该区域陆续发现了储量丰富的油气藏。为研究沿开江-梁平海槽东部和大池干井构造带的深部电性构造和控制油气运移的隐伏断裂,布置了6条大地电磁测线,共采集181个测点的大地电磁测深数据,覆盖面积为15 km×6 km。对实测数据作二维TM模式反演,揭示了四层地电构造,总厚度约为10 km。在探测区中部下方,存在厚度为4km的低电阻率层。研究区内断裂组合为北东向逆冲断裂系,被一组北西向断裂错断。这种区域地质构造对油气藏聚集具有重要的控制作用。研究成果对分析该区油气藏的地质构造具有参考价值,并对盆地边缘类似油气勘探工作具有借鉴意义。

Shibaozhai area is located in the northeast Sichuan Basin in Southwest China.In recent years,oil and gas reservoirs with abundant reserves have been discovered in nearby areas.Six magnetotelluric(MT)survey lines were arranged to investigate the deep geoelectrical structures and hidden faults that controlled the hydrocarbon migration along the eastern Kaijiang–Liangping trough and Dachiganjing tectonic belt in this area.The MT sounding data for 181 sites,which covered an area of 15×6 km,were collected.Twodimensional transverse-magnetic-mode inversion of the data revealed four geoelectric layers with a total thickness of approximately 10 km.A low resistivity layer with a thickness of 4 km was discovered in the middle of the exploration area.The combination of faults within the study area revealed a northeast-direction thrust-fault system,which was displaced by northwest-direction faults.The regional geological structures played a significant role in controlling hydrocarbon and gas accumulation.The results of this study could be beneficial in analyzing the geological structure of hydrocarbon reservoirs in this area and can be extended to the exploration of areas in the boundary of a basin.