2. The Second Well Cementation Branch of CNPC Bohai Drilling Engineering Company Limited，Tianjin 300280，China;

3. Development Department of Huabei Oilfield，Ｒenqiu 062552，Hebei，China;

4. Technique Department of CNPC Bohai Drilling Engineering Company Limited，Tianjin 300450，China;

5. Gas Storage Management Department of Huabei Oilfield，Ｒenqiu 062552，Hebei，China;

6. Tianjin Branch of CNOOC，Tianjin 300452，China

intervals，the productivity of the sandy conglomerate reservoir has been significantly descended． In this study，a weakly acidic surfactant is developed and applied to decrease the viscosity of oil and remove plugs out of reservoir．The weakly acid is used to dissolve part of the clay minerals and unclog the seepage channels． The pyrolysis and emulsification function of the surfactant can decrease the viscosity and thus improve the seepage capability of oil．The method was successfully applied in well treatment，through which the daily well production increased from 0. 38 m3 /d to 63. 91 m3 /d． The double targets of‘production increase and reservoir protection at the same time’have

been realized．

removing   Jilantai oilfield