Aer Sag is characterized by multi-provenance, near-provenance, narrow facies belt and rapid facies change. The sand bodies present longitudinal stack and cross-binding, and the distribution of permeable sand bodies is complicated, so it is difficult to ascertain the distribution of the favorable reservoirs, which seriously affects the calculation of reserves. This paper carried out the fine reservoirs prediction by using joint inversion technique, and determined the thickness variation trend and the distribution range of permeable sand bodies. The result of calculation measures up to requirement of reserve calculating, which provides major parameters and references for the calculation of the proven reserves. The actual application proves that using joint inversion technique to predict permeable sand bodies can obtain a high accuracy and meet the demands of reserves calculation for oilfield.