Multiwell pads have become a norm in unconventional reservoirs with wells having multistage, multiperforation-cluster configuration. The complex jungle of wells and horizontal laterals under the surface of the earth has raised the complexity of pad optimization and hydraulic fracturing to a next level. Modeling the hydraulic fracture systems correctly is key for optimizing well and stage locations. Even in the case of noncomplex, planar fractures, the interaction amongst the fractures, which is also known as stress shadow effect, can lead to uneven fracture growth. In the case of complex fracture networks, the fracture interaction can be even stronger due to typically higher fracture density. Therefore, stress shadowing is a key element in reservoir modeling for shale plays in the framework of hydraulic fracturing. The sequence of stage placement in the pad and their treatment can also have a significant impact on the reservoir contact.

The zipper fracturing technique, involving the simultaneous and back-to-back stimulation of horizontal wells on a pad, has been rapidly adopted by multiple operators in the last few year across various shale plays in North America. The technique has achieved its popularity due to increased efficiency and reduced turnaround time for a multiwell pad. The method has been effective in saving tens of millions of dollars for operators by accelerating the pad development cycle. Apart from improved completion efficiency, pads that have run zipper fracturing have shown improved production from their counterparts in the same field that have been completed without zipper fracturing. The impact on hydraulic fracture growth due to stress shadow from offset wells’ hydraulic fracture systems is a major contributing factor for this difference. Depending on the time spent between the stages, the extent and magnitude of stress shadow will change to dictate the growth of the offset well hydraulic fracture stage.

Proper reservoir modeling can help optimize the well location and spacing, completion staging, and optimizing hydraulic fracture treatment designs as well as their sequence. This study reviews and discusses the application of stress shadow modeling for various treatment sequences for multiple wells in a pad—and use of numerical reservoir simulation for optimal pad development strategy. The results assess the impact of managing the fracturing sequence and accounting for the delay in time between stages, growth of hydraulic fractures and their interference amongst each other, distribution of proppants and fluids, and reservoir drainage through numerical simulation for unconventional reservoirs.

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