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FRINATEK-Fri prosj.st. mat.,naturv.,tek

Mechanisms for CO2 storage in the presence of residual oil

Alternative title: Mekanismer for lagring av CO2 i nærvær av gjenværende olje

Awarded: NOK 11.3 mill.

CO2 storage in mature oil reservoirs is an attractive strategy because infrastructure exists, and the geology is known from the oil production phase. Such reservoirs often contain residual oil trapped as disconnected ganglia in the pore space after water injection. Thus, a CO2 storage strategy requires knowledge of how water and this residual oil influence the CO2 flow pattern and storage mechanisms, and conversely how CO2 invasion impacts the behavior of the residing fluids. CO2 dissolution in oil and water will change the fluid properties, lead to oil swelling, and potentially alter the wetting state of the porous rock. These processes can serve both oil recovery and CO2 storage. Cyclic injection, which often is a realistic storage option when CO2 availability is low, can optimize residual trapping, but reservoir simulation is challenging because flow mechanisms are complex. Little is known about how the behavior changes when residual oil ganglia are present. This project will bring forth advanced pore-scale models for three-phase flow to explore how CO2 dissolution in the presence of water and oil affects residual CO2 trapping, oil trapping and mobilization, capillary pressure, relative permeability, and hysteresis behavior over multiple CO2/water invasion cycles in porous rock. The models will be validated against a wide range of advanced CO2/oil/water pore-scale experiments provided by our international research partners. The validated pore-scale simulators will be released as open-source so that users can make their own calculations with the aim at reducing the number of required lab measurements for CCUS operations. The project will also bring forth suitable macroscale three-phase flow models that capture the effective three-phase flow behavior observed at pore scale. This is a first necessary step towards reliable simulation of large-scale CCUS operations in mature oil reservoirs. The project has just started, and so far, we have worked on the development of pore scale models for three-phase flow (Task 1).

CO2 storage in mature hydrocarbon reservoirs is an attractive strategy because infrastructure exists, and the geology is known from the oil production phase. However, such a strategy requires knowledge of how water and residual oil influence the CO2 invasion pattern and storage mechanisms, and conversely how CO2 invasion impacts the behavior of residual oil ganglia and water. The presence of residual oil in such reservoirs introduces CO2 dissolution in oil and water that can serve both recovery and storage. Cyclic injection, which often is a realistic option due to low CO2 availability, can optimize residual trapping, but reservoir simulation is challenging because flow properties and hysteresis are complex. Little is also known about how this behavior changes when residual oil ganglia are present, and CO2 dissolution alters the oil properties (like viscosity and density), which lead to oil swelling and potentially changed wetting state of the porous rock. This project will bring forth advanced pore-scale models for three-phase flow to investigate how CO2 dissolution in the presence of water and oil affects residual CO2 trapping, oil trapping and mobilization, capillary pressure, relative permeability, and hysteresis behavior over multiple CO2/water invasion cycles in porous rock. The models will be validated against a wide range of advanced CO2/oil/water pore-scale experiments provided by our international research partners. The validated pore-scale simulators will be released as open-source so that users can make their own calculations with the aim at reducing the number of required lab measurements for CCUS operations. The project will also bring forth suitable macroscale three-phase flow models that capture the effective three-phase flow behavior observed at pore scale, including fluid-ganglia dynamics. This is a first necessary step towards reliable simulation of large-scale CCUS operations in mature hydrocarbon reservoirs.

Funding scheme:

FRINATEK-Fri prosj.st. mat.,naturv.,tek