(31c) Injection-Induced Reservoir Damage and Its Effect on Early Stage Production

This paper presents a numerical model for proppant injection and hydrocarbon production for unconventional operations. Both injection and leakoff fluids into the formation help determine the size and conductivity of fractures, as well as the water envelope damage near fractures inside the formation. This can impact the transient depletion of the reservoir, particularly during early production. The effect is studied in terms of reservoir permeability, production rate, and phase distribution.

Methods, Procedures, Process

This model considers planar fracture geometry; the computation domain includes the volume between two parallel fractures extending from the wellbore to the reservoir boundary. The model can alternate between injection and production modes, with gas, oil, and water phases included, and gas-oil phase transition allowed. Therefore, leakoff and production in the formation are simulated based on the pressure and phase saturation fields. A fracture-stimulated horizontal well in the Eagle Ford is used to validate the model, both for injection-induced water damage and production.

Results, Observations, Conclusions

The production model is set up in a commercial software code and can be used for sensitivity analysis and fracture design and optimization. It is also tested on the Eagle Ford horizontal well for historical matching and production prediction. The injection process accounts for the discrepancy between the model prediction and historical data, particularly during early production. With the water envelope size considered, both the production rate and the phase distribution are substantially different than they would be otherwise. This impact can be applied to transient analysis to provide better understanding of the reservoir depletion during early production and pressure fields near the fractures, as well as the production decline curve. The results of comparison with production decline curves from the Eagle Ford well show good agreement during this stage.

Novel/Additive Information

Because of the geometrical simplicity and detailed account for physical/chemical effects, the developed method can be used to perform fast economic analysis and design and optimization of fracture stages with a detailed account for planned fracture geometry and reservoir and condensate properties, including phase transitions. The effectiveness of the method makes it possible to run this analysis as an application for wellbore simulators, reducing the need to combine it with reservoir solvers.