Seismic Velocity Research In Quele Of Kuqa Depression Of Tarim Basin In Xinjiang

The mountainous structures in Kuqa depression of Tarim basin are very complicated. As geological conditions above and under ground are not fulfill the assuming multifold coverage requirements (horizontal surface and interface, homogenerous medium), signal to noise ratio of seismic data is very low. Structure form in time domain seismic cross-section often distort,such as high point deviate, attitude of stratum (direction and angle of dip) deform away from the true. By using various mapping methods, the elements of structural trap (closed area, closure, macro-axis, minor-axis, location of high point) and buried depth change. Seriously, structural forms in time-depth domain vary a lot due to the distortion in time domain which is caused by velocity. So it's difficult to discover and identify a trap, also in well location defining when we explore and develop oil. Thus, in order to ascertain a favorable structure accurately, we endeavor to establish a set of velocity analysis method and research the mapping techniques which are effective in foreland basin areas. The method and techniques are based on seismic-geological data which is associated with well drilling and logging data.We make out a research route, according to the unique geological feature in Quele and present problems in seismic survey:①Analyse prospect wells' vsp, acoustical wave and different synthetical geologic well logging datum, recognize the relationship of different stratum, their buried depth, dip and lithology.②Analyse shallow layer velocity's changing patterns that have a better seismic data quality and higher velocity spectrum grade.③Analyse oil geophysics conditions' effects on velocity. These conditions (fault, formation lithology, formation's buried depth, strata dip, cream-salt bed's thickness etc) influence trap's ascertain.④Apply generalized relationship and method to velocity research in Quele, Kuqa depression, establish regional velocity field in work area and analyse its trueness. ⑤By comparing velocity backfill model inversion data with other research outcomes (prestack depth migration), we develop a more appropriate velocity analyzing scheme, and establish various velocity fields in different ares.