The Palaeogeomorphic Characteristics And Geological Significance Of The Permian Longtan Formation In Northwestern Sichuan

Picking up a set of sedimentary marine carbonate rocks sourceed from Maokou Formation of Permia located in the North West of Sichan basin,which is influenced by the Dongwu movement,under the damage of weathering denudation and leaching and dissolution of meteoric fresh water,which form into numerous solution pole and fracture,all the damages made it possible to be the effective reservoir of natural gas.By researching the sample,the development of Karst reservoirs has an inseparable connection with the ancient landform,as we've barely studied the ancient landform,it limits the deep research of reservoir and the exploration deployment.With the breaking efforts through the natural gas,especially from Long004-xl and according to the new standards all three oil-testing wells gained industrial airflow again,the evidence of exploring ensures us there's much exploring potentials in Maokou Formation of Permian.The essay which is applying adequate regional Seismic Data,combining the restricted drilling among the survey area,umpty practical measurement and 1:200000 outcrop sectional profile data,based on Stratigraphic Division,Correlation Horizon Calibration and explanation,recognize the rule of residual strata distribution on the survey area,adopting the methods of residual thickness,recovering the ancient Karst landform of Maokou in the survey area,more importantly researching its sedimentation-tectonic significance and petroleum geological significance.The survey results indicated that,the ancient Karst landform of Maokou in the survey area appears to be flatlands landform pattern generally,based on that,it could be devided into three geomorphic unit types:karst platform,karst slope and karst groove,Karst terraced terrain can be devided into hill depression,monadnock,shallow depression etc,recognize the Karst slope and the hill depression and monadnock in the Karst platform is under the impact of dissolution mostly,which is beneficial to the development of Karst reservoirs,which is the key of the subsequently exploring deployment,the best reservoir are the Jiange-Cangxi and Jiulong mountain.meanwhile,the karst groove landform from Guangyuan to the North of Wangcang may be connected with the erosion grooves,which has subsequential impact on the formation and evolution of guangwang trough,which foreseen the Synsedimentary faulting which is caused by the Emei tafrogeny can became active,which controlled the formation and the evolution of deposits in the survey area,lead to the formation of Embryonic Form trough.