China Petroleum Exploration ›› 2023, Vol. 28 ›› Issue (5): 117-125.DOI: 10.3969/j.issn.1672-7703.2023.05.010

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Analysis and application of seismic velocity characteristics in areas with near surface conglomerate development: a case study of YKB area in Kuqa piedmont zone

Han Bo1,Wang Baocai2,Luo Fusong2,Zhang Yuyue1,Han Bo2,Xia Yongtao2,Ding Wei2   

  1. 1 Sinopec Geophysical Research Institute Co., Ltd.; 2 Research Institute of Exploration and Development, Sinopec Northwest Oilfield Company
  • Online:2023-09-15 Published:2023-09-15

Abstract: In seismic exploration in the piedmont zone, stacking velocity is generally used for variable velocity mapping. However, there is few study on the influence of the near surface conglomerate on the stacking velocity of the underlying strata, and there is a lack of effective methods for stacking velocity correction. The wedge-shaped model is applied to simulate the near surface conglomerates, and the characteristics of seismic wave travel time-incident angle curves at various locations are analyzed. In addition, by taking YKB area in Kuqa piedmont zone as an example, seismic forward modeling is conducted to verify the results, which confirm that an abnormally high stacking velocity is formed below the pinch out points caused by the near surface high-speed conglomerate, resulting in a lateral velocity variation of “low-high-low-high” from the inner-fan to the outer-fan. Based on this understanding, the stacking velocity is corrected by velocity trend line method, and the result map is compared with that by well velocity constraint method. The results show that the formation occurrence in the structural map obtained by the velocity trend line method is closer to the measured results, with a smaller depth error, which proves the effectiveness of this method in the near surface conglomerate development area in the piedmont zone with low level of exploration.

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