Method for drilling a borehole from one cased borehole to another cased borehole

摘要

In a method for drilling adjacent to a cased known first borehole a second borehole in a predetermined direction the following steps are carried out for a number of along hole depths di: measuring components of gravity acceleration and magnetic field (earth & casing); determining direction parameters alpha i; deriving magnetic polestrength components, Bp1,i and Bp2,i; applying Bp1,i/Bp2,i=s1,i/s2,i and determining deviations of the predetermined direction; and controlling drilling direction of the second borehole.