Zipper fracturing is a method of sequencing frac jobs in multi-well pads that helps increase operational efficiency and reduce stimulation time for a pad. This technique involves stimulating several wells in a pad in a prescribed sequence of stages. In this work, we provide a thorough assessment of the various factors impacting the effectiveness of zipper fracturing treatments and provide a methodology for selecting an optimum sequence of fracture stages.

A fully implicit, parallelized, 3-D, pad-scale reservoir-fracturing simulator is used to simulate the dynamic propagation of multiple, non-planar fractures from multiple treatment wells while capturing the stress interference between fractures. This interference is captured both on an intra-well as well as an inter-well scale. Interaction between fractures propagating from different wells is found to be dependent on pad design, completion design, and reservoir parameters. We evaluate the effectiveness of the stimulation operation by comparing the impact of operation decisions on the created fracture geometries and simulated productivity of the propagated fractures using seamless fracturing-reservoir simulations.

The simulation results are used to understand the impact of well spacing, stage spacing, staggering of zipper-frac wells, lagging of stages during zipper fracturing, size of the frac job, stress contrast in the reservoir and rock properties. Using multi-cluster fracturing simulations and accurate proppant distribution calculations in the wellbore, we consider the impact of various operational decisions mentioned above on the distribution of proppant in the created fractures. We observe that fracture closure during shut-in of a stage impacts the created fracture geometries. This affects the proppant distribution in the fractured stages. The impact of the operational decisions on the fracture conductivity degradation during stimulation is also captured using seamless fracture-reservoir simulations. We show that the results obtained from these simulations can help design pad-scale operations to maximize the fracture-reservoir contact area or improve the productivity of the wells.

In this work, for the first time, we assess the impact of zipper fracturing on well productivity by performing coupled fracturing-reservoir simulations. The software is used to simulate fracture propagation and fracture closure during shut-in and production. The results obtained from these simulations recommend an optimized fracture sequencing, stage lag and staggering strategy to maximize the productivity of the pad.

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