Migration refers to movement to a particular place for a particular purpose, such as feeding or breeding, and then return to the former site. I do not think that migration is an appropriate term to use for tortoise movements. Each tortoise has a home range or activity area. A home range is the area in which a tortoise travels, feeds, sleeps, courts, and has its burrows. This is the area with which the tortoise is familiar.
Large tortoises have large home ranges and small tortoises have small home ranges.
Females are more sedentary than males and do not move about as much, so they probably have smaller home ranges. Large males are known to occupy home ranges over 0.75 square mile. Tortoises appear to have a good sense of compass direction. They also are very familiar with local landmarks. They can travel to find burrows in a straight line.