Improving Horizontal Well MPD by using a Dual-Channel Drillstring

Abstract

The Wisting Field is located offshore in the Barents Sea north of Norway. The field development requires drilling and completion of horizontal wells in a narrow pressure window, which is challenging for conventional technology. The Reelwell Drilling Method (RDM) provides a solution for managed pressure drilling (MPD) to mitigate these challenges. Based on the use of dual-channel drillpipe, RDM enables the pressure gradient in the openhole section to be held constant and nearly independent of the drilling fluid flow rate. RDM provides low-energy drilling, i.e., efficient drilling and hole cleaning when using low flow and low-drillstring rotation speed. This allows drilling of horizontal sections within a small pressure window and limits drillstring fatigue in high-dogleg applications. In order to start qualification of RDM for the Wisting Field, a horizontal trial well was drilled in fall 2018 at the Ullrigg Drilling and Well Test Centre, located at the NORCE Norwegian Research Centre in Stavanger, Norway. The goal for this trial well was to prove the dual-channel drillpipe capability to perform low-energy drilling, i.e., low-rotary speed, low flow, and stable downhole pressure gradient. The trial well had a challenging geometry with up to 14°/30-m build rate, as required for the field. The 9½-in. horizontal section was drilled in order to check the performance of the RDM and start the qualification of the RDM for the Wisting Field. The trial well was drilled with a low-flow motor, i.e., with flow rates around 700 lpm. The string rotation speed was held lower than 5 rpm to limit drillstring fatigue in the high-dogleg section of the well. Efficient drilling and hole cleaning of the 9½-in. horizontal hole section was demonstrated. The results from the trial confirm the predicted performance for the RDM. The results indicate that RDM can keep well pressure gradient within the required window and mitigate the drilling challenges for the Wisting Field. The RDM architecture with return flow in the inner string represents a major advantage to avoid cuttings build up in the well, challenges with laminar return flow, formation wash-outs, mechanical down hole dynamics and ECD control by low energy drilling.