Abstract: As the reservoir in Wendong oilfield is characterized by low permeability,high mineralization of formation water and high clay mineral content,high- pressure and lack of injection has become serious through the development process. Therefore,the technology of swelled clay shrinkage agent has been developed to lower pressure and enhance water injection, on which the normal acidizing method has failed.In the end the application of 8 wells in 4 blocks of Wendong oilfield shows the water injection pressure for single well has decreased 2.6 MPa,water injection increased 23 m~3/d,and average increased oil for single well is 63.8 t and the accumulative increased oil for corresponding wells is 510.4 t.