Fault Identification And Distribution Characteristics In Lunnan And Sangtamu Oilfields

Lunnan and Sangtamu oilfields are located in Lunnan topographic high within Tabei uplift.The Tabei uplift can be divided into 6 second-order tectonic units.The Lunnan topographic high is bounded by Luntai fault to the north,northern depression to the south,and Cao lake and Halahatang Depression to the East and the West,respectively.This thesis focuses on the fault identification,fault development period,and fault distribution in the Lunnan and the Sangtamu oilfields.In order to achieve the aforementioned objectives,seismic sequence stratigraphic interpretation and synthetic seismogram are carried out on the Lungu 2 eastern block of Lunan and Sangtamu oilfields.Based on the seismic data of Lungu 2 eastern block,the faults developed in Lunnan and Sangtamu oilfields are recognized.Due to the low quality seismic data of the Lunnan and the Sangtamu oilfields,the automatic seismic gain technique is used to strengthen the seismic reflection characteristics in order to facilitate the identification of the faults on seismic profiles.The automatic seismic tracking technology is also used to track and recognize the hidden faults in the key areas.On the basis of seismic interpretation,fault identification,and reconstruction of the fine velocity field model of the Lungu 2 eastern block in Lunan and sangtamu oilfields,the abnormal velocity points are eliminated,and the T0 map and the structural map of the key surfaces of the target blocks in the Lunan and the sangtamu oilfields are constructed.In order to restore the periods of the fault movement,the structural evolution profiles are made.Then the fault cutting layers are summarized by observing the seismic profiles of the study area.Through the aforementioned methods,the distribution maps of the fault plane are constructed for further delineation of the characteristics of the fault distribution.Through observation of the seismic profiles,identification of the forms of the faults,and understanding of the fault evolution,the fault development characteristics are summarized.Furthermore,the different fracture cutting zones,active periods,and fracture characteristics are summarized to divide the fault zones in the study area.Based on the characteristics of the micro faults in the key surfaces of the target areas,various seismic attributes,and the ant body automatic seismic tracking technique,the development patterns of the key surfaces of the targets are summarized and low-relief structures are identified.The study area mainly developed three groups of strike faults,east-west,northsouth and north-east directions.The fault development period in the study area can be divided into four stages,the first stage,late Caledonian period due to the weak extrusion stress,such as the Lungu West and the Lungu East strike slip fault,and the second period,late Hercynian due to the north-west thrust stress formed by the north-west thrust stress,such as the Lunnan fault and the Sangtamu fault;the third stage,Indosinian-Yanshan period,the north-east compressional stress changed from north to south to South West to the north-east and North-South echelon faults,such as the wild goose shear zone in the south of the Sangtamu,and the fourth stage,late Himalaya,end of tectonic movement,develop regulating fault.