Borehole Tortuosity Effect on Maximum Horizontal Drilling Length Based on Advanced Buckling Modeling

Abstract

Borehole tortuosity is inherent to the rock drillin g process and can be defined as the unwanted undulations from the planned well trajectory, such as borehole spiraling in vertical sections or slide-rotary pattern when using steerab le mud motor in horizontal sections. It can sometimes comp romise the success of the operation, especially in horizontal drilling, where additional drag can lead to problems while ru nning completion strings. Latest advancements in drill string mechanics have shown that borehole tortuosity (often ignored in standard buckling theories) plays a key role on the onset of buckling . The maximum horizontal length achievable by a given directional system (such as conventional rotary bottom hole ass emblies, steerable mud motors and rotary steerable systems) depends not only on the severity of the borehole tortuosity along the horizontal section, but also on the build rate of t he curve section. This paper shows the results of a sensitiv ity analysis using an advanced buckling model where different bore hole geometries have been studied.