Back to Basics: Revisiting Proppant and Fluid Selection for Unconventional Reservoirs Using a New 2D Slurry Transport Model

Abstract

It is often thought that in ultra-low-permeability unconventional reservoirs, proppant does not play a significant role in productivity because any proppant effectively results in a relatively infinite fracture conductivity. Although with over 75% of the treatment jobs pumped with slickwater in the shale reservoirs due to its cost benefit, it is also thought that slickwater has limited solids carrying capacity. Overflushing may compromise productivity by creating near-wellbore pinchouts. The study presented here aims to test some of these conventions through the use a new high-resolution slurry transport model in unconventional reservoirs. Hydraulic fracture propagation and solids transport are simulated across multiple wells and reservoir settings to measure the production performance of unconventional reservoirs. Wells completed in the Eagle Ford formation are studied using an integrated earth model built to capture the reservoir geology, petrophysics and geomechanics. A pseudo 3D model for fracture propagation has been coupled with a fine grid numerical simulation of proppant and fluid transport in hydraulic fracture. The transport model can distinguish and demarcate the corresponding bridging resolution. This allows capturing the effect of slurry with proppant bypassing bridged 2D elements. Multivariate analysis of over 50 cases with various combinations of hydraulic fracturing fluid with viscosity ranging from 1.5 cP (slickwater) to 362 cP (crosslinked gel) and various proppants ranging from 100 mesh to 20/40 proppants are evaluated using the 2D transport model to determine the impact on production. Additionally, various pumping schedules ranging from 750 lbm/ft to 3,000 lbm/ft are evaluated. Parametric sensitivity of the overflush fluid type and volume has been studied to measure the impact on proppant dislodgement in the near-wellbore area. Production performance for all the scenarios is studied through numerical simulation and an economic analysis workflow to evaluate the matrix for fracturing fluid and proppant selection.