Influence of nozzle structure on effectiveness of jet grouting operations and its optimal design

The jet grouting technique is gradually adopted for improving gas production from reservoirs yielding a low permeability. Ensuring the quality of jet grouting products involves optimizing the efficiency of jetting gear including nozzle. This paper investigates the effect of nozzle structure on efficiency of jet flow and delineates the optimal nozzles for jet grouting operations. A tri-fold approach was adopted including field experiment, nu-merical simulation, and multicriteria decision analysis. The numerical and experimental results show that, of the 10 structures investigated, 4 achieved a steadiest jetting pressure attenuation along different standoff distances, whilst satisfying the requirement of driving pressure of 30 MPa with a flow rate of 70-80 L/min. The converging section plays a critical role in the conversion of viscous force within the nozzle. The study shows that the dominant flow regime is governed by the nozzle's parameters L2 and theta and the optimal structure of the nozzle has been designed, i.e., d = 2.4 mm; theta = 26 degrees; D = 4.24 mm; L1= 10 mm; L2 = 4 mm; and L3 = 21.10 mm. The numerical results agree well with the experimental observations, proving that the optimal design can be adopted for enhancing jet grouting operations.