Detailed Integrated Asset Model Boosts Water Injection Potential in Giant Fields

Abstract

Integrated asset models for the water injection networks have been developed to complement the optimization of oil production while honoring system constraints and balancing offtake across the reservoirs. A well-calibrated asset model enables operation closer to the system constraints leading to higher water injection rate potential and the ability to better allocate water to the right drainage regions. The integrated model comprises individual well models linked to a surface network model. While the well modeling itself is uncomplicated due to single-phase flow conditions, complications arise when hundreds of wells are tied together via multiple injection clusters linked together to provide optimum routing flexibility. Some of the routing options give rise to pressure imbalances in the network and require special attention to set up and solve. The wells fall into three distinct categories. Category 1 includes wells that belong to injection clusters constrained by pump capacity. These wells may inject into different reservoirs; hence optimization requires redistributing a fixed volume according to voidage replacement ratio considerations. Category 2 consists of wells that inject just below fracturing pressure. Any increase in rate would require stimulation, in this case matrix acidization. The wells are therefore ranked based on the expected rate increase from a fixed injectivity improvement, such as 10, 15 or 25%. The predicted injectivity index improvement is then supplied to the network solver to predict the potential water injection increase at field level, considering all the system constraints. Category 3 comprises wells that should be ramped up after checking for well integrity and verifying the fracturing conditions.