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 d.sub.i :P P measuring components of gravity acceleration and magnetic field (earth & casing);PPdetermining direction parameters . sub.i ;PPderiving magnetic polestrength components, B.sub. p1,i and B.sub.p2,i ;PPapplying B.sub.p1,i /B.sub. p2,i =s. sub.1,i /s.sub.2,i and determining deviations of the predetermined direction; andPPcontrolling drilling direction of the second borehole.