In order to reduce the damages from conventional water-based workover fluids，such as water，formation water，water based foam in Kalaza group reservoir of Shengbei oil and gas field，Tuha basin，a kind of solid-free and low-density oil-based foam workover fluid was developed. The properties of workover fluid were analyzed and the workover fluid was applied on 5 wells in Kalaza group reservoir. The results showed that the density of solid-free and low-density oil-based foam workover fluid composed of 30% formation water，70% crude oil，0.25% oil-based foaming converting agent DRzh-3，0.20% oil-based foam stabilizer DRxc-2，0.45% oil-based foaming agent DRfoam-2，was 0.34—0.90 g/cm3. The foam of workover fluid had high intensity，over 24 hrs stable time and strong anti-leakage blocking ability. The permeability recovery ratio of core after polluted by workover fluid was greater than 94%. The workover fluid had good resistance of high temperature（120℃）and compressive strength（10—11MPa）. According to the characteristics of oil-based foam fluid，the complete set of workover technology measure was improved.After this technology applied in 5 Wells on site，the effective rate was 100%，and the average recovery time of each well shortened 3 days. The pollution to reservoir damage was reduced，the leakage was less，and the performance of workover fluid was stable. Furthermore，the construction on site was convenient with low cost. It could effectively solve the water sensitivity and water locking during workover operations in low pressure reservoirs.