Instantaneous threshold method and dual-ends pressure balance method are commonly used to test minimum threshold pressure gradient

but they are time-consuming and hard to ensure the accuracy of measurement data.The test results of pseudo threshold pressure may be slightly higher by using method of "differential pressure-flow" under constant confining pressure.Based on the above considerations

a set of integrated experiment process is designed

and the method of unsteady threshold-pressure balance is formulated.Also the way to implement the method of "differential pressure-flow" is optimized.The accuracy of the test results is ensured by using precise equipments in the experiment process

and the process is suitable for a wide range of core permeability test of threshold pressure gradient.Test results meet the expectation when this method is applied to well cores in Tuha oilfields

and this method can become a common measurement in the lab.