Rotary Steerable Directional Jetting Service Successfully Delivering Step Change in Directional Well Design for Soft Sediment Formation in Deepwater Nigeria

Abstract

This paper describes the successful technique to start a kickoff below the 36-in. conductor casing with much higher dogleg severity (DLS) capability than a conventional motor directional drilling method in a soft sediment formation by using a rotary steerable system (RSS) equipped with directional jetting. This technique uses a rotary steerable system (RSS) equipped with directional jetting to provide the operator with a step change in directional well design for reaching shallow reservoirs with inclinations close to horizontal. The challenging aspect of the well design was that only 650m (2133ft) of TVD was available to perform the directional work. This section consisted of weak and soft sediment formations that did not support conventional directional drilling methods. To address the operator's challenge, it was determined that a RSS configured for directional jetting could deliver the higher DLS for the optimal well trajectory. This system combines two techniques, rotary steerable and directional jetting, to achieve the directional objective. This field-proven application was successfully used by several operators, as described in SPE-173057-MS, and applied in this deepwater low-UCS environment. The extensive engineering evaluation, using finite-element analysis and torque-and-drag calculations, confirmed the bottom hole assembly (BHA) design was technically feasible without compromising safety and drilling efficiency. Three wells successfully delivered all directional objectives with this technique. The highest inclination was recorded in the top hole as planned; the sailing angle was lower compared to other wells drilled with conventional directional drilling methods, and the target sands reached at an angle close to horizontal. Completions ran without issues. This technique delivered above 3°/30m DLS in the deepwater soft formation and all future wells for this operator will use this technique for the tophole drilling.