南方海相碳酸盐岩分布区1994—1996年电法勘探找油实践

1994—1996 Electrical Exploration in the Regions of Marine Carbonate Rocks,Southern China

运用 MT 法、EMAP 法、CSAMT 法、TEM 法和 LOTEM 法等多种方法,在南方开展了区域构造和局部构造两大类电法勘探。电磁波易穿透高阻的碳酸盐岩,对低阻层较为敏感,适合于在高阻岩层中寻找低阻目标。实践表明,电法勘探适用于大区评价、盆地优选、选择有利保存地区、发现局部构造、寻找潜伏礁体和区域性盖层、识别火成岩体以及落实推覆构造等方面。南前陆盆地带的四条 MT 测线揭示了所经过的主要构造样式有基底卷入型和盖层滑脱型二种;江汉盆地和秦岭一大别山的 MT 测线资料重新处理解释,揭示了挤压和剥蚀程度随远离造山带而减弱。江苏太湖水上 MT 法勘探,显示了其下古生界是一个以隆凹相间为主要特征,被火成岩、推覆构造等复杂化了的块体。采用密集布点的中、高频 MT 法、EMAP 法以及 MT 和 CSAMT 法结合等在广西桂中坳陷、十万大山盆地以及贵州秧坝地区开展了找礁试验,找到了一些可供进一步勘探的礁体目标。

Two types of electrical exploration,the exploraton of areal structure and regional structure,have been done in southern China with the methods of MT,EMAP,CSAMT,TEM and LOTEM etc.during 1994—1996.Electromagnetic wave could penetrate into high resistance carbonate rocks easily,and is sensitive to intercalated low-resistance beds.It is suitable to find low-resistance targets in high-resistance rocks.The practice shows that electrical exploration has great vitality in region evaluation,selection of advantageous basins and preservation regions,finding local structures,buried bioherms and regional cap rocks,distinguishing the mass of igneous rocks,and vesifying nappe structures etc.Four MT lines through the southern belt of foreland basins reveal that main structural patterns under the lines are the base-involved pattern and the cover-decollement pattern.The reprocessing and reinterpretation of MT line through the Jianghan Basin and Qinling-Dabieshan Mountains reveal that compression and erosion weaken from the mountains to the basin.The MT aquatic exploration on Taihu in Jiangsu province shows that Lower Palcozoic under the lake is a block which is characterized by alternate uplifts and sags complicated by igneous rocks and nappe structures.The tests explorating for bioherm have been taken in Guizhong Depression,Yangba area,Shiwandashan Basin with the methods of MT,EMAP and CSAMT.Some bioherm targets was found which are worth further explorating.The electrical exploration could be an effective non-seismic geophysical exploration method making up for the defects of seismic exploration.