A calculation method of minimum distance between wellbore survey error ellipsoids

With the wide application of cluster wells and infill wells in oilfields, higher requirements are put forward for the wellbore anti-collision analysis. Wellbore separation factor is a common index for anti-collision analysis. However, different calculation methods of the distance between wellbore error ellipsoids lead to great differences in results, so that a new method was presented to calculate the minimum distance between wellbore survey error ellipsoids to satisfy the application requirements. Based on the coordinate transformation and error ellipsoid calculation, the formulae for calculating the distance between wellbore error ellipsoids were derived by the center vector method; the minimum distance between wellbore error ellipsoids was further solved using the optimization theory; a rapid solution strategy was also studied to calculate the separation factor accurately and rapidly. The case analysis show that the new method can guide the wellbore anti-collision risk assessment better than other calculation methods, which has application value in the cluster well design and directional drilling.