Mechanical Behavior of Reamer During Enlarging a Super Large Diameter Directional Hole

Abstract

In order to take full advantage of an offshore platform, sometimes a super large diameter directional hole could be drilled from one notch, and then two technical casing strings are run and cemented in the hole side by side to form the so-called monocular double-well. By reasons of wellbore stability and equipment ratings, a small pilot hole has to be drilled firstly and then be reamed to the size needed. Through traditional bottom hole assembly mechanical analytical method, lateral forces of guide shoe and reamer were calculated. Comprehensive analysis showed that the reamer should have side cutting ability, a guide cone prior to reamer is necessary, the guide shoe should not have side cutting ability but should have a certain axial drilling ability, the length of guide collar should be selected carefully, and two-step reaming strategy should be adopted for super large directional borehole.