3D Seismic Data Interpretation And Favorable Target Prediction In Shulu Sag

Shulu sag,a typical half-graben with down faulting at the eastern boundary and overlapping at the western boundary,is located in the southern margin of Ji Zhong depression.Shulu sag has small area,relatively low abundance,low transformation rate of resources and high potential of exploration.The stratum of Paleogene in Shulu sag is dominated by sand-shale alternating layer,forming a good reservoir-seal assemblage.In addition,the exploration target in this area is also dominated by the structural reservoirs,however,exploration precision is limited by the inaccuracy of layer interpretation,the appearance of axis piercing and the shortage of fault system division.Meanwhile,the alluvial conglomerate located on the top of buried hill is beneficial to the preservence of oil and gas which in turn increases the difficulty to indentify the top surface of buried hill and then becomes one of the most critical factors restricting the exploration of such reservoirs.To overcome the problems mentioned above,in the basis of previous studies,combining regional stratigraphic data,3D seismic data,log interpretation results,and known oil and gas reservoir data,3D seismic data structure interpretation and favorable target prediction in the study area have been carried out under the guidance of geophysics and tectonic geology.Firstly,according the results of synthetic seismogram,we obtain the seismic response characteristics of conglomerate layer and the top surface of buried hill as well as stratigraphic contact relations.All-region closure interpretation has been carried out based on the reflection characteristics of the unconformity of Ning Ji uplift zone;the characteristics of onlap and truncation in Shu Lu slope break belt as well as the characteristics of strong amplitude and continuity.Futhermore,the stratigraphic interpretation and fault interpretation of the main target strata of the paleogene system are carried out by using three-dimensional structural interpretation technology and 6 types of faults are obtained according to the statistics of the fault geometry and kinematics.Type?-? and ?-?-? correspond to oil-migrating faults;Type? and ?-? correspond to screened faults;The fault throw of Type? is small but it can also play a role in the accumulation of oil and gas;Type? corresponds to the late adjustment faults,which are not found in Shu Lu sag.Finally,based on the structural interpretation results,the types of buried hill structural traps and shallow structural traps were divided,and the structural traps were evaluated at four target strata in combination with other accumulation factors.The results indicate that there are 5 traps of class ? and 21 traps of class ? and the favorable targets are as follows: No.5 trap and No.6 trap of reflector Tg,the No.10 trap of reflector T5,the No.5 trap of reflector T4 as well as the No.10 trap of reflector T2.