A starting pressure prediction of thixotropic cement slurry: Theory, model and example

•An exponential model for thixotropic fluid is improved.•The model can describe relation of gel strength with resting time, shearing time.•A prediction model of starting pressure for cementing stop pump is proposed.•The prediction model can guide modulation ingredient of thixotropic cement.•Pressure drop is contributed by the additional pressure of thixotropic cement.

In this study, index model of thixotropic fluid is improved, and further on this basis, a prediction model of starting pressure of thixotropic cement slurry is created. Fann viscosimeter with heating unit will be adopted to measure static shearing force and shearing stress. The thixotropic model will be validated by test. Test of starting pressure estimation proves that starting pressure increases rapidly at the early stage of pump shut-down but slowly against the increasing of shut-down time.