Optimized Drilling Performance by Innovative Application of High-Build-Rate RSS to Sidetrack from Vertical Pilot Hole in Challenging 3D Wells in Unstable Formations

Abstract

An onshore oil E&P operator in the Middle East region had been looking to optimize performance while delivering complex 3D profile wells. The target was to find a solution for performing an openhole sidetrack from a plugged back 8 ½" vertical pilot hole and drill the deviated hole to land horizontally at the top of the reservoir, while following a complex 3D profile trajectory that demanded a minimum continuous dogleg severity (DLS) of 6.75°/100ft across unstable shale formations where conventional RSSs can achieve only up to 4.4°/100 ft DLS. In previous wells, sidetrack from plugged back pilot hole and drilling of 8 ½" landing section was performed in two runs, first one with a motor assembly and the second one with RSS. However, having two runs resulted in longer operational time and lower average ROP. Previous attempts to drill with a conventional RSS across unstable shale had failed to achieve the required DLS and this practice had been eliminated by the operator. Based on the above, high-build-rate RSS (HRSS) was proposed to overcome theaforementioned challenges to drill the section in one run. This paper mainly discusses the advantages of accurately kicking off and performing an openhole sidetrack, from a cement plug at the top of an unstable shale formation, and drilling ahead while achieving required high build rates in a single run with new HRSS. This new tool enables deeper kickoff, shorter landing point departures, improved ROP, and smooth borehole in soft or hard formations in complex 3D well profiles, meeting all of the desired objectives and saving rig days, operator costs and resources. Eleven cement plug sidetracks from vertical and shoe-to-shoe drilling runs to section TD were done from Q1 2012 to date using the HRSS with 100% success. The applications of the HRSS described in this paper are innovative applications designed through thorough planning and risk mitigation. As a result, significant achievements in cost optimization and drilling efficiency enhancement have been realized.