College of Geo-exploration Science and Technology, Jilin University, Changchun 130026, China

Aiming at solving the problem of low resolution and precision for the detection of oil reservoirs by normalized full gradient of gravity, the authors use downward continuation of the derivative iterative method to calculate normalized full gradient of gravity. The Fourier transform and this method are both used in the model tests. The influence of harmonic number N, depth and fullness coefficient on G^H field are analyzed. The results show that compared with Fourier transform, this method is less affected by the influence from harmonic number N, and the resolution of G^H field to reservoirs is higher and the inversed depth is more accurate. The validity of the method is verified by practical application.