Full System Analysis to Predict the Reliability of a Wastewater Disposal System; a Hydraulic Simulation-Based Approach

Abstract

Abstract The increase in water production from mature fields calls for continuous monitoring of wastewater disposal (WWD) system capacities. The three main components of any WWD system are discharge pumps, pipeline's network and disposal wells. Situations may arise when the full system capacity is constrained by the flow performance of one or a combination of these components. Subsequently, produced water volumes are reduced by closing high water cut oil producers. The grave and critical importance of such systems necessitates proactive diagnosing and forecasting of WWD performances. Plant-A injects 45 thousand barrels per day (MBD) of wastewater into five disposal wells. Historical system performance showed an increase in the pump discharge pressure that has nearly reached its maximum operating limit. A variation in injection performance among all the five disposal wells was observed. This variation is attributed to the different completion designs and reservoir inflow performances of the five subject wells. A 14 km flow line of varying sizes connects the disposal wells to two parallel discharge pumps. These pumps are designed to inject the abovementioned rate at a discharge pressure of 800 psi at current conditions. A full system analysis of Plant-A disposal network, utilizing hydraulic simulation techniques, was performed to model the current injection performance. The goal of this comprehensive study of the disposal system was to explore all possible root causes of the discharge pressure increase. In addition, the hydraulic simulator forecasted several feasible and recommended scenarios to eliminate this high discharge pressure. The five disposal well's inflow and outflow performance relationships were generated and calibrated using actual injection data. Network flow analysis was performed to account for both frictional and gravitational pressure losses in pipelines and flow restrictions using sophisticated software. This high accuracy model improved the decision making process and an optimized solution was put into effect based on the simulation results.