Abstract: In order to safely realize the reuse of inefficient twinhole-in-monobore well slots and achieve the purpose of stabilizing and increasing production in the oilfield, the shallow distance between Well M1 and Well M2S1 is accurately calculated by correcting wellhead coordinates, datum height and analyzing the impact of errors on the trajectory, analyzing the possible conditions in cutting and fishing operations, formulating the technical casing cutting and fishing scheme of Well M1, and optimizing the cutting points, cutting BHA and milling tools to ensure that the case of Well M2S1 will not be damaged during abandonment of Well M1, so as to avoid kick accident. The accurate design data ensures the safety of on-site abandonment operations, realizes the reuse of twinhole-in-monobore well slots, and provides technical measures for stable production of the oilfield.