| Denan subsag is located in the northeastern part of Linqing depression,the fan-shaped subsag is composed of the main lowlying area and a minor one(Taitousi lowlying area,to the north of Well De-5)with Bixuedian nosing structure in the middle,and they separately extended to the northwest and northeast.Formation of Denan subsag was controlled by basement fault.Sedimentation of Denan lowlying area was controlled by Denan fault,while Taitousi minor lowlying area was controlled by West Tuqiao fault,and the two faults buildup a double graben structure.Based on massive seismic data and drilling data,the author divided Denan subsag into several structural levels,and carried out systematic research in faults characteristics,evolution history and genesis of extensional structures.Finally,the paper come to the following conclusions:1.Faults development characteristics can be summarized as: multiple phases,multiple directions,multiple types,and multiple combination patterns.Most faults extended to the northeast(NE),approximately east-west(EW),with a few pointed to the northwest(NW).2.Regional extensional stress(NW-SE)during Eogene result in well development of extensional structural patterns,such as concave-convex shaped half basin,graben,etc.Relative NNE-NE extending faults controlled direction of subsag and distribution of structural belts,as a result,E-W extending structural framework took shape.Lateral transfer zones caused by NWW directional faults cut with fault zones caused by NNE-NE ones,and resulted in structural differentiation between the north and the south.3.Fault development can be divided into 4 stages,they experienced 3 regional tectonic transition periods,and finally formed structural framework of two lowlying area with a convex in between.The paper deepened understanding in aspect of Eogene structural characteristic in area of 2000km2,and provided good proofs for further study in exploration orientation and targets evaluation. |
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