Characteristics Of Typical Detachment Zones In Huanglongchang And Wubaiti 3D Areas And Their Seismic Structure Interpretation

There are multi-detachment layers with different vertical strata in East Sichuan Basin,such as gypsum-salt layer,mudshale and coal-bearing strata those layers with weak mechanical properties,and East Sichuan basin can be divided into a series of multi-level detachment system by these layers.The sedimentary strata can be divided vertically into several oil and gas ranges by detachment layers.However,it is necessary to discuss deeply in the various aspects of the multi-level detachment deformation system.Firstly,the study for the detachment layers lithological composition,thickness and distribution range is short of detail.Secondly,the research which used 3D seismic data to predict the detachment layers distribution in the well constraint conditions,and to describe the regional or local detachment layers feature accurately are also rare.Thirdly,It is also scarce to study the structure of detachment layers with high resolution 3D seismic data.Fourthly,there are also few researches on the influence of detachment layers on upper and lower stratum tectonic deformation and oil and gas preservation conditions.For the above contents that we need to study further,Selecting the Huanglongchang area and Wubaiti area where located in the intersection area between the arc thrust belt protruding southward of south Daba Mountain and the NE fold belt of East Sichuan Basin as the research object.Based on the comprehensive analysis of geological and drilling data,and fine structural interpretation of 3D seismic data,firstly,the lithology combination and well logging response characteristics of the four main detachment layers(The Cambrian gypsum-salt layer,Silurian Longmaxi mudshale layer,Permian Longtan coal-bearing layer and Triassic Jialingjiang gypsum-salt layer)are analyzed,and the seismic reflection feature of four detachment layers has been defined by seismic forward modeling,the feature identification templates of main detachment layers are also established.Then,the two reseach areas are developed the cover-decollement pattern which Cambrian gypsum-salt layer as main detachment layer,the overlying strata tectonic deformation are controlled by the detachment fault in connection with the Cambrian gypsum-salt detachment layer,and underlayer is low uplift.But there are some differences in tectonic deformation between the two study areas for reason that the plane distributive characteristics of Triassic Jialingjiang gypsum-salt layer and the orientation of major principal stress are different.Moreover,in well constraints condition,the distribution of Triassic Jialingjiang gypsum-salt has been predicted through the seismic inversion,meanwhile,the distribution characteristic of detachment layers has been described by seismic attribute in this place without well.Finally,in conclusion,the tectonics relate with Cambrian gypsum-salt detachment layer and Triassic Jialingjiang gypsum-salt detachment layer will be the main object of exploration,and the uplift regions under Cambrian gypsum-salt layer will be another favorable targets for deep layer exploration.