Impacts of Proppant Flowback on Fracture Conductivity in Different Fracturing Fluids and Flowback Conditions

Abstract

Multistage hydraulic fracturing is used in horizontal wells to increase the production of tight oil. Fracturing fluids are used in hydraulic fracturing to ensure proppants are suspended, but fluid residuals can cause formation damage and reduce rock permeability; meanwhile, fracture conductivity can be further reduced due to the flowback of proppants during the early stage of production. In this study, steel plates and hydraulically fractured reservoir rocks are tested in a modified API cell to understand the impacts of flowback rate, fracturing fluid, and closure stress on proppant flowback and fracture conductivity. When the closure stress increased from 21 to 30 MPa, retained permeability decreased by slickwater from 35.71 to 29.84% in steel plates; during the flowback, more than 47% of proppants flowed back, and the fracture conductivity increased by 10 times under 21 MPa, which shows the limitation of the API method on the study of proppant flowback. When shale plates are used, the critical flow rate that prevents the proppant flowback was found to be 5.5 × 10 –4 –1.6 × 10 –3 m/s for the 30/50 mesh sands (around 55–340 m 3 /d for a typical horizontal well), and the retained permeability decreased from 23.33 to 22.86% due to an increase of closure stress from 21 to 30 MPa. Results of this study can guide the optimizing of the flowback scheme in the field that minimizes the proppant flowback in different fracturing fluids.

Fracture Conductivity Prediction Based on Machine Learning

“…Hydraulic fracture quality is the core of hydraulic fracturing quality, and fracture conductivity is particularly important. − The prediction of fracture conductivity is not only the basis of fracture optimization design but also one of the key parameters to determine the effect of hydraulic fracturing. − At present, the main research method for fracture conductivity is based on indoor testing methods. Xiao et al took carbonate rock as the research object and experimentally studied the effects of acid erosion, proppant embedding depth, and different proppant sizes and acid injection on fracture conductivity during hydraulic fracturing and acid fracturing; Guo et al conducted tests on steel plates and shale to understand the effects of flowback rate, fracturing fluid, and closure stress on proppant flowback and fracture conductivity; Sun et al used ceramic and quartz sand proppant obtained from Changqing Oilfield in China. For example, the fracture conductivity under different proppant mixing ratios was evaluated through experiments; Tariq et al .…”

“…9−11 At present, the main research method for fracture conductivity is based on indoor testing methods. Xiao et al 12 took carbonate rock as the research object and experimentally studied the effects of acid erosion, proppant embedding depth, and different proppant sizes and acid injection on fracture conductivity during hydraulic fracturing and acid fracturing; Guo et al 13 conducted tests on steel plates and shale to understand the effects of flowback rate, fracturing fluid, and closure stress on proppant flowback and fracture conductivity; Sun et al 14 used ceramic and quartz sand proppant obtained from Changqing Oilfield in China. For example, the fracture conductivity under different proppant mixing ratios was evaluated through experiments; Tariq et al 15 studied the effects of different acid fracturing fluids, rock hardness, and surface roughness on the fracture conductivity of carbonate rocks through experiments.…”

Influence of Shale Mineral Composition and Proppant Filling Patterns on Stress Sensitivity in Shale Reservoirs

“…The effectiveness of supporting agents in the formation is influenced by factors such as temperature, pressure, and their own properties, with the migration of supporting agents being challenging to observe directly [24][25][26]. Numerous scholars have extensively researched the conductivity of fractures using API conductivity meters and rock slabs [27,28]. It is worth noting that the smooth surface of rock slabs may not accurately simulate the fracture morphology formed after fracturing in reservoirs [29].…”