PROPPANT MIGRATION WITHIN A ROUGH HYDRAULIC FRACTURE

Abstract

Hydraulic fracturing creates a fracture network that enhances the hydrocarbon flow from the tight reservoir where the proppant migration determines the conductivity of the propped fracture, and thus, the well productivity. Core observations from the Hydraulic Fracturing Test Site (HFTS) show that hydraulic fractures are denser than initially designed and most of them are not well propped. Understanding the proppant migration in the thin and rough fracture is crucial to the optimization of the pumping scheme in the field. In this work, a transparent rough fracture model is duplicated from a hydraulically fractured outcrop by the epoxy resin with the dimension 300 mm × 300 mm × 300 mm. The settling rate of sands is quantified in this rough fracture model under different mimicked pumping conditions, from which a model is built to help estimate the growth of propped hydraulic fracture under different pumping rates, sand ratios, sand diameters, and fracturing time during field operations. The model corrects the classic Stokes' law for proppant settlement within a narrow and rough fracture. Results indicate that the equilibrium height and migration rate of the sandbank increase with the sand ratio and decrease with the pumping rate. After being compared with results obtained from Fluent simulations, a numerical model is further proposed to predict the growth of a propped fracture in the field scale.