Abstract: In this paper, we provide a whole set of method to develop a high precise gigantic velocity field. And we build a giant velocity field in Tarim basin. This velocity field is about 10.2×10⁴km², which equals to the total areas of Jiangsu province, and 8 km deep. In accordance with the special problems of giant velocity field, we use automatic discarding abnormal values, ridding intersection velocity closing error, and horizontal slice velocity calibration, extend VSP well. By comprehensively using velocity spectrum, VSP, sonic log data, and database technique, we establish a high precision velocity field. With this velocity field, we test two VSP wells which were completed using velocity field data. The predicted max absolute error is 54m/s, the average is 37m/s; the max relative error is 1.87%, the average is 1.26%. According to the data given by this velocity field, we can plot a depth structural map, which correctly disclose a petroliferous structure that we can not show it on the TO contour map.

Key words: Tarim basin, velocity distribution, velocity spectrum, VSP, sonic log