Abstract: In this paper,the EZFLOW drilling fluid system and PRD drilling fluid system are compared in the light of the requirements for drilling fluid used in horizontal well drilling and optimized completion.In this paper,a brief introduction is given to the improvement requirements and composition principle of the EZFLOW system,the application requirements and the main points of performance control,the field operation measures and the successful application in the XX Oilfield.The results indicated that the EZFLOW system has very good carrying capacity,super high shear force and relative low shear rate viscosity.It is favorable to the suspension of drilling cuttings,and can be used to improve the hole cleaning ability,and to overcome the difficulty of carrying sand in horizontal or high angle wells at low pump speed or stopping pump.The operation flow is free from breaking glue,which is favorable for reservoir protection and simplifying of the types of additives,being well adapted to marine transportation and health and safety environment.It is of great significance both in increasing production and reducing cost,being suitable for XX oilfield and similar fields in Bohai Oilfield.