Abstract: The shielded temporary blocking technique is one of key measures for reservoir protection. Since "Seventh-five-year" H Plan, Huabei Oilfield has made research on this technique. Polymer drilling flu id and polysulfonate drilling fluid are respectively used to meet the different drilling depths. The shielded temporary blocking drilling fluid is prepared when the modified asphalt and the superfine calcium carbonate or the oil-soluble temporary blocking agent are added into polymer drilling fluid system; and/or the oil-soluble temporary blocking agent and the superfine calcium carbonate are added into the polysulfonate drilling flu id system. Lab test indicates that the shielded temporary blocking drilling fluid has a satisfactory result, with API fluid loss less than 5 ml, HTHP fluid loss less than 15 ml and restored core permeability more than 65%. In application of 11 wells in 4 blocks, completion logging interpretation indicates that the skin factor is less than zero, and plugging ratio is less than 1. Oil production of these wells is increased significantly in comparison with the offset wells.