Numerical analysis on the transient cavity flow field during liquid nitrogen jet fracturing

Abstract

Liquid nitrogen jet fracturing is expected to provide a novel treatment for reservoir stimulation. To verify its feasibility, the flow fields in cavity at different times are simulated by CFD method. Then the transient temperature and pressure distributions are analyzed. Based on the cavity pressure distributions, the pressure boosting effect is evaluated. The results show that the nitrogen gas close to the cavity entrance is easily pushed out and the temperature in this region decreases quickly during liquid nitrogen jet fracturing. However, the temperature at the cavity bottom increases firstly at the squeezing action of liquid nitrogen jet and then decreases due to the heat transfer induced by the low temperature liquid nitrogen jet. Compared with water jet, the liquid nitrogen jet can generate equivalent pressure boosting effect in the cavity. Due to the compressibility of nitrogen gas, the pressure boosting process of liquid nitrogen jet fracturing falls behind the hydrajet fracturing. This study identifies the pressure boosting capability of liquid nitrogen jet and can further provide theoretical basis for the researches of this fracturing treatment.