An innovative simulation methodology was developed that incorporates fine scale features of complex reservoir geology, the details of hydraulic and natural fracture networks, and compositional modeling to account for the injected propane-oil interaction. The simulation models were used as an operational tool to make key design and operational decisions in the Bakken Propane Injection EOR field test and were critical to the success of the test.

Multiple reservoir model realizations were built using a fine simulation grid, dual porosity/dual permeability option, multi-component compositional fluid description, and robust representations of the hydraulic and natural fractures. Geo-mechanical simulation was applied for hydraulic fracture representation in the individual stages of horizontal and vertical wells. A software tool was developed for the hydraulic fracture representation in the structured simulation grid matching geometry, porosity, and conductivity of the geo-mechanical simulation. A discrete fracture network (DFN) was used to represent the natural fractures.

Each model was history matched with all the production and pressure data obtained during the pre-propane injection period. The models were updated continually with the field test surveillance data and were used to forecast production phase oil and gas rates and propane concentrations in the produced gas.

The model predictions guided field operational strategies optimizing propane injection volumes and soaking duration. The effective optimization methodology was applied for optimizing operational strategies.

The simulation predictions of incremental oil, water, and gas production rates and the propane concentration in the produced gas were corroborated by field data, indicating the robustness of the simulation methodology.

Novel methodologies were used for representing hydraulic fractures in the structured grid simulation model and for optimizing field enhanced oil recovery (EOR) operational strategies. These features enhanced the robustness and predictive capability of the reservoir simulation workflow. Validation of the modeling workflow with field EOR test data has given us the confidence to apply it for design and operation of upcoming field pilots.

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