Sustainable reservoir optimization: A numerical study of the Snorre water diversion field pilot using IORSim

Waterflooding is a commonly used secondary recovery technique in oil production, where water is injected into a formation to maintain pressure and push oil toward the adjacent production wells. In reservoirs with high permeability contrasts, poor sweep efficiency and a non-uniform displacement front cause large unrecovered hydrocarbon volumes. As the reservoir depletion progresses and the water cut increases, the energy costs and CO 2 emission become unfavorable relative to the produced oil. In 2013, the Norwegian Continental Shelf (NCS) Snorre operators implemented a large-scale sodium silicate injection pilot to divert the reservoir water flow, improve volumetric sweep efficiency, and reduce CO 2 emissions. This study utilized a geochemical simulation tool (IORSim) to numerically history match and predict the Snorre water diversion field pilot impact on field performance, reservoir life span, and CO 2 footprint. While an industry-standard reservoir simulator was used to compute the velocity fields of the fluid phases (e.g., water, oil, and gas), IORSim calculated the sodium silicate transport, polymerization, and permeability reduction along the temperature front. Instead of simultaneously solving the geochemical reactions in all grid blocks, IORSim identifies upstream and downstream cells to treat chemical species balance as iterative one-dimensional problems. Besides ensuring numerical stability, IORSim allows computation-efficient reactive subsurface modeling using splay tree calculation. In the first IORSim simulation, the injection and production well rates were constrained by the historical field rates to visualize the sodium silicate polymerization along the temperature front and to history-match the injection and production well pressures. The numerical model revealed two phases of gelation: (a) Early near-wellbore gelation due to formation water and silicate slug mixing and (b), in-depth gelation five to ten months after field pilot initialization. The second IORSim model compared the field pilot reservoir performance to conventional waterflooding by constraining the injection and production wells by pressure. Between 2013 and 2019, the thief zone plugging lowered the water production by 1.18 MSm 3 while the water cut decreased by 2.9%. Moreover, due to the 1.34 MSm 3 injection water reduction, the CO 2 emissions associated with the water injection pump decreased by 8931 t (34.4%). • Topological sorting, splay tree calculations, and host simulator/geochemical solver coupling mechanism allow IORSim to seamlessly and efficiently add geochemical interactions to full-field reservoir problems. In contrast to conventional reservoir simulators, the IORSim reactive transport models capture geochemical phenomena that can significantly affect field operations (e.g., Near-wellbore and In-depth gelation). • The IORSim Snorre field pilot history matching revealed two phases of gelation: (A) Early Near-wellbore gelation due to formation water and silicate slug mixing and (B) In-depth gelation five to ten months after field pilot initialization. Compared to the pre-pilot water injection, tracer data confirmed a 100% to 200% displaced volume increase due to water diversion. • The field performance analysis confirmed successful thief zone blocking, improved volumetric sweep efficiency, and a 2.9% reduction in water-cut. In light of CO 2 emissions and taxation, the combined effects of reduced water injection (-1.34 MSm 3 between 2013 and 2019) and reduced produced water volumes (-1.18 MSm 3 ) highlight the environmental and economic attractiveness of In-depth water diversions. The CO 2 emissions associated with the injection pump were reduced by 8931 tons or 34.3%.