Managing the High Water Cut Behavior in a De-Saturated Reservoir and Maximize the Oil Gain

Abstract

Abstract A new technology utilizing the Autonomous Inflow Control Device (AICD) has been used in horizontal wells producing from a viscous oil reservoir to restrict the unwanted water breakthrough and maximize the oil gain. The added benefit of greater reservoir contact has met with increased differential drawdown across the horizontal section to manage the reservoir heterogeneity. AICD is an active flow resistance element distributed along the length of the horizontal well-bore section to delay and reduce the proportions of the water breakthrough. The AICDs impose a relatively strong resistance for low-viscous fluids over the high viscous oil. This is due to the changes in the flow area internally in the AICD. With this technology, oil production can be increased while restricting the water inflow into the wellbore. The AICD operates without the need for human or surface interventions and electric or hydraulic power. AICD technology has been piloted in two new wells in two fields located in South Oman. The reservoir contains viscous oil (400-600 cp) and exhibits high inflow potential due to favourable rock properties and strong bottom water aquifer. Horizontal wells have been used to maximize reservoir oil contact and improve recovery from the reservoir. The wells, in general, produce oil with very high water cut (>95%). Two horizontal wells were drilled recently, and each well was completed with AICDs along a completed lateral length of 500 m. The AICDs managed in bringing down the water cut to less than 5% from 95% observed in the surrounding wells. The production behaviour has been sustained for nearly a year now. The success of the AICD trial has opened the doors for its wider use in reservoirs containing viscous oil. The AICD also has been tried in existing wells where it managed to reduce the gross and the water cut by 50% and increase the oil gain by 100%. Plans are also in place to extend the AICD trials in existing wells and reap the benefits by maximising oil production while decreasing the unwanted water production.