Gel damage has been identified as the most severe damage effect on gel-fractured well productivity. The reduced effective fracture length and fracture conductivity can significantly decrease the initial production rate and the ultimate recovery, especially for tight reservoirs. In this paper, we conduct numerical studies on fracture cleanup effects, and explore procedures for improving post-fracture production.

To effectively simulate fracturing fluid rheology and transportation, a dual continuum method is employed in our model. Gel residue inside the fractures is determined based on gel and breaker reaction dynamics from experimental data. Increased gel concentration in slurry injection, increased breaker concentration during fracture clean-up, and the flowback procedure are simulated to quantify the gel damage phenomenon. Features such as non-Darcy flow through fractures and polymer adsorption/desorption are included in the model. Parametric studies on the gel and breaker concentrations, reservoir properties, and flowback designs are also discussed.

Our studies determined that interactions between breaker and gel can be fully integrated into numerical simulations. Tested with a variety of gel and breaker concentrations as well as the reaction dynamics, the numerical model is robust in quantifying the gel damage phenomenon in the fracture. Detailed numerical evaluations of gel damage effects with severe gel-damage zone inside the fracture are demonstrated in this paper. High gel residue concentration is observed at the tip of fractures due to high yield stress during flowback, which reduces the effective fracture drainage. Cleanup efficiency is highly dependent on the gel and breaker interactions. Based on parametric studies, optimized gel/breaker concentrations and sufficient interaction time can significantly reduce the gel residue inside the fracture and provide possibilities of having less gel damage in hydraulic fractures. The results provide new observations about improving well productivity through proper gel/breaker selection and flowback design.

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