Separation Factor
"Separation Factor" also known as "Error Ratio" is used for assessing the collision risk of two wellbores. It is calculated as a ratio of center-to-center distance and the sum of semi-major axis of error ellipse of the two wellbores. The separation Factor of 1 indicates that the error ellipses of the two well bores touch each other. A separation Factor of less than 1 means that error ellipses overlap and a Separation Factor of more than 1 means that the ellipses don't overlap.