The Effect Of Wellbore Stability In Naturally Fractured Reservoirs

Abstract

Abstract Wellbore instability all over the world accounts for a significant in Non-Productive Time (NPT) in well drilling and completions and incurring high cost of drilling as well as increasing safe risks. Real time analysis of data and geomechanics (understanding the rock properties and stresses) has continuously improved the stability of wellbores in the world. Some of the issues cost by this instability are the most common of these losses are: borehole enlargement, cavings, washouts, stuck pipes, deformation of the casing and amongst others. Numerous wellbore instability problems related to drilling through potentially natural fractured reservoirs/formations have been reported. Most of the this reported formations are been characterized by number of macro and micro scale bedding planes and/or networks of natural fractures which weakens the mechanical strength of the rock and the producibility of potential of the rock matrix. This term paper reviews instabilities issues in Naturally Fractured Reservoirs (NFR), natural fracture reservoir failure mechanism and highlights the effect of instabilities in NFR as well as proper well placement in the NFRs. This paper also looked at wellbore solution in permeable and impermeable formations, borehole failure analyses, drilling strategies to mitigate instabilities in naturally fractured reservoirs and other counter-measures dealing with wellbore instability. The review shows that well design, drilling fluid design, minimizing lateral vibrations of drill pipe and good drilling practices are critical in solving wellbore stabilities in naturally fractured reservoirs.