Hydraulic Fracturing Treatment Design Considerations for Effective Proppant Pillar Construction Available to Purchase

As an alternative to conventional proppant pack placement, propped pillar-fracturing promises more effective and conductive fractures that enable hydrocarbons to flow through open channels. Recent experimental and numerical studies confirmed that viscous fingering phenomena can be used to develop a proppant pillar-fracture type placement: High-viscosity, proppant-laden fluid can be placed, and then a low-viscosity clean fluid is pumped to carve pathways through the proppant-laden fluid in a dynamic, continuous process. However, the created channel pattern was found to be significantly dependent on fracture geometry and treatment design parameters such as injection rate, fluid pulsing time, and fluid viscosity ratio.

The objective of this study is to extend the numerical investigation and normalize it to develop a treatment design methodology for constructing proppant pillars throughout the created fracture. A computational fluid dynamics (CFD) model was constructed using commercial CFD software, simulating the flow of fluids inside the fracture and the resulting proppant pillar generation. The study focused on the effects of surface injection rate (1 to 40 bpm/cluster), pulsing time (5 sec to 5 min), and viscosity ratio (from 2 to 20) between the two injected fluids to develop correlations between these parameters and the created fracture geometry.

Based on numerical results, the viscosity ratio chosen to achieve the proppant pillars allows the use of conventional crosslinked fluid without a hindered settling agent. In these designs the settling of proppant into pillars can be made to occur after the end of the stimulation treatment. Controlled settling of proppant from a crosslinked proppant-laden slurry allows channel formation and creates wider propped fracture-width pillars as compared to current industry pillar-fracturing treatment techniques. The optimum channel pattern has small channel sizes, remains open under closure stress, creates more channels throughout the entire fracture area and maintains good communication between unpropped areas. A new dimensionless term, Dimensionless Stage Volume (V_SD), is presented to describe the channel pattern inside the fracture. Smaller V_SD numbers resulted in smaller and more distributed channels. Therefore, it is highly recommended to select and design a proppant pillar-fracture treatment to achieve the lowest V_SD possible and create the optimal channel pattern.