Effect of parameters on threshold pressure of sandstone tested by water jet

Threshold pressure of sandstone is of great importance in water jet drilling, which is regarded as an economical method to enhance the oil productivity. However, the effect of the parameters on threshold pressure jetted by water, which helps decide the pump pressure in the field test and guide the feeding velocity, remains unknown. In this paper, two nozzles are chosen as the jetting tools, after which the structure of the nozzles are revealed. Artificial sandstones with various properties are made as rock samples, and then the threshold pressure of the rock samples is tested comparatively by self-made experimental system. The results are analyzed by dimensionless method and data analysis software, until then a simple regression equation is presented in this paper and the experimental data and prediction data fit well. From the analysis, threshold pressure is proportional to 0.84 power of compressive strength, which indicates its major role of contribution, while the porosity and permeability play a subtle role in threshold pressure There is a little difference of the minor factors of threshold pressure between the nozzles, which is correlated with the rock breaking mechanism by water jet. Rock breaking velocity is also discussed in this paper. The results presented in this paper can provide guidelines for the applications of water jet drilling.