Study On Time-depth Conversion Method Of Complex Structure In The Southern Margin Of Junggar Basin

The Southern margin of Junggar Basin is one of important replace fields for petroleum exploration in Xinjiang oilfield. During its early period, lots of oilfields such as Dushanzi oilfield, Kayindike Oilfield, Hutubi gas field, Mahe gas field and so on and petroleum structures like Horgos anticline, Tugulu anticline, Anjihai anticline, Xihu anticline and so on have been found here, which shows rich oil-gas resources.Favorable targets of the south Junggar Basin basically are complex piedmont structures, generally having a feature of dual surface and subsurface complexity. With lower quality seismic data, obtained structure map has low accuracy by using time-depth transform after seismic velocity field building. Later, after analyzing the early failure for exploratory wells, it is thought that structure implementation is an important factor to restrict the exploration for oil and gas in this area, in which time-depth conversion is a technical bottleneck in restricting the precision of structure map.This study, based on analysis methods to time-depth conversion for the south Junggar Basin, sorts out the problems and deficiencies of mapping the piedmont complex structure. Besides, it discusses seismic velocity field building in this area and the methods to varying velocity mapping. We implemented the target research area by regarding the Gumudi 3D and Changshanl 3D in the eastern region of the south margin as an elaborate target, and made a system research from aspects of data processing, seismic data interpretation and time-depth conversion method study and so on, preliminary summed up a time-depth conversion method with higher accuracy, being suitable for the south Junggar Basin and advantageous targets.Relied on research and production project, and separately against the features of seismic prestack time migration data and prestack depth migration data, this study preliminarily forms structure implementation technology, including area drilling velocity analysis method, regional seismic velocity field building and varying velocity mapping method, processing and interpretation technology of high resolution for complex structure and complex structure accurate velocity modeling technology. These technologies got applied in the south and Gumudi 3D area and made good effects. Through this study, we had velocity mapping method research in the south Junggar Basin. Besides, in Gumudi 3D and Changshanl 3D areas, target areas researching accurate velocity, we proposed multiple drilling wells targets and got adopted. Lots of drilling wells among these propositions got petroleum discovered and good oil shows, expanding the petroleum exploration results in the eastern region of the south Junggar Basin.Verified by true drilling, adopting those technology methods mentioned in this study can effectively improve the accuracy of time-depth conversion. The error, between true drilling hierarchy and design hierarchy in target layers at Gumudi 3D and Changshanl 3D areas drilling wells. By summarizing the successful applying experience showed in Gumudi 3D and Changshanl 3D areas, we can find that technical results achieved in this study have a strong realistic promotion significance, which provide better technical reference of accurate implementation of other complex structures within the range of the south Junggar Basin.