Numerical simulation on the state of fluids along the string of gas storage well

To analyze the force applied on the string of gas storage well and determine the erosion position, it is crucial to fgure out the motion state of natural gas in the tubing string in the process of gas injection and production. In this paper, a physical model used to simulate the fowing process of natural gas along the tubing string of directional gas storage well was established on the basis of casing program and operation parameters. Then, the velocity and vorticity along the string and the distribution of pressure close to the wall in the defecting section were researched by means of numerical experiment. And fnally, the infuential laws of injection-production pressure difference, hole deviation angle and tubing ID on the pressure close to the wall of string were analyzed. It is indicated that the state of fuids inside the tubing string is affected by injection-production pressure difference and casing program, and the fow velocity of natural gas and its pressure close to the wall fuctuate the moment it fows into and out of the defecting section. The velocity and dynamic pressure along the string decrease as the well gets deep. Erosion point is located at the connection line between the radial line at the maximum dogleg angle and the central line of string from the infow end to the outfow end of defecting section. As the injection-production pressure difference increases, the average pressure range ratio between the outside and the inside of the bend at infow and outfow ends increases obviously. With the increasing of hole deviation angle, the average pressure range ratio between the outside and the inside ofthe bend at the infow end increases while that at the outfow end decreases. And with the increasing of tubing ID, the average pressure range ratio between the outside and the inside of the bend at the infow end decreases while that at the outfow end increases.