Following successful field calibration and a high-accuracy blind test (described in URTeC: 4245581), a robust refrac sensitivity and optimization study was conducted using a fully integrated hydraulic fracturing and reservoir simulator. The goals of this study were to identify key drivers of refrac performance, provide guidelines on refrac candidate selection, and deliver direct optimizations of refrac designs for field trials. Four Bakken-calibrated models served as the foundation for the study, each representing typical well configurations within the play. Each model included two Middle Bakken refrac wells and two Three Forks offset wells, representing 10-year-old wells. The original completions were characterized by small fluid and proppant volumes, calibrated fracture initiation points, and crosslinked gel. Refrac completion design applied typical modern industry practices using slickwater, with relative variations in cluster spacing, larger proppant, and fluid loadings. The sensitivity analysis workflow varied one parameter at a time to quantify its impact on refrac uplift and identify the most impactful parameters. Finally, an optimization workflow was carried out to identify the optimum economic refrac completion designs for field trial. Sensitivity results indicate that original fracture spacing is the dominant factor influencing refrac uplift, with the effect being most pronounced when fractures from adjacent wells are spatially overlapping. The normalized prerefrac oil production and the distance to infill wells are the next most impactful parameters, while fluid and proppant loadings show moderate effects.
Optimization shows that wells refractured with longer stage designs deliver comparable production to those completed with shorter stages, but at a notable increase to refrac incremental rate of return. Also, this study found that optimum refrac design depends on field stress profile: areas with contained fractures benefit from bigger refrac jobs, while areas with growth out of the pay zone favor reduced refrac fluid loading and higher proppant concentrations. The presented workflow provides a robust framework for physics-based refrac design optimization and economic improvement in unconventional assets. The workflow isolates the impacts of each variable and identifies the most influential parameters affecting refrac uplift. Based on this evaluation, recommended refrac candidates may include wells with a substantial unstimulated portion of the lateral, lower relative production performance compared to expectations, and adequate spacing from nearby infill wells to minimize interference. These criteria help prioritize opportunities where refrac can deliver the greatest incremental value.