Settling of Spherical Particles in High Viscosity Friction Reducer Fracture Fluids

Ghith Biheri,Abdulmohsin Imqam

doi:10.3390/en14092462

Ghith Biheri, Abdulmohsin Imqam

Open Access

https://doi.org/10.3390/en14092462

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Abstract

Investigating the key factors that impact fluid rheology and proppant static settling velocity in high viscosity friction reducers (HVFRs) is a critical aspect for successful proppant transport in hydraulic fracture treatment. In this study, the rheological properties of HVFRs were tested at various temperature ranges (i.e., 25, 50, 75, and 100 °C) and different HVFR concentrations (i.e., 1, 2, 4, and 8 gpt). Three sizes of spherical particle diameters (i.e., 2, 4, and 6 mm) were selected to measure the static settling velocity. The fracture fluid was tested in two fracture models: an unconfined glass model and a confined rectangular model with two fracture widths (7 and 10 mm). The settling velocity in the confined and unconfined models was measured using an advanced video camera. HVFR results exhibited acceptable thermal stability even at higher temperatures, also the viscosity and elasticity increased considerably with increasing concentration. Increasing the temperature cut the friction reducer efficiency to suspend the spherical particles for a significant time, and that was observed clearly at temperatures that reached 75 °C. Spherical particles freely settled in the unconfined model due to the absence of the wall effect, and the settling velocity decreased significantly as the HVFR concentration increased. Additionally, the fracture angularity substantially slowed the proppant settling velocity due to both the wall effect and several types of friction. This research provides insights into the rheological parameters of a high viscosity friction reducer as a fracturing fluid and its efficiency in transporting particles in bounded and unbounded fracture networks.

Highlights

The settling velocity plays a major role in transporting sand particles during hydraulic fracturing operations, so it is significant to investigate the major parameters that impact the freely settling velocity of particles
high viscosity friction reducers (HVFRs) are shear-thinning fluids, where increasing the shear rate leads to increasing shear stress
The results indicate that the settling velocity velocity was faster at a low HVFR concentration of 1 gpt compared to the high HVFR

Summary

Introduction

The settling velocity plays a major role in transporting sand particles during hydraulic fracturing operations, so it is significant to investigate the major parameters that impact the freely settling velocity of particles These factors include rheological properties of viscoelastic fluids, wall effect, wall roughness, and presence of other solid particles [1,2,3,4,5,6]. HVFRs have been used in many basins in the United States such as Marcellus, Fayetteville Shale, Eagle Ford, Bakken, and Delaware basin, and most of them reported a reduction in the chemical required by around 30% compared to slickwater treatments [14,15] These applications require flexibility and simplicity of polyacrylamide stability under harsh conditions such as high reservoir temperatures [16,17]. The use of guar can cause severe damage to shale rocks, which can significantly affect the conductivity [18]

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