The impacts of fracturing fluid viscosity and injection rate on the near wellbore hydraulic fracture propagation in cased perforated wellbores

Abstract

Copyright 2015 ARMA, American Rock Mechanics Association.In this study, hydraulic fracturing tests were conducted on 150 mm synthetic cubic samples. The borehole drilled in the center of the sample was cased and perforations were created in the samples. A true tri-axial stress cell was used to simulate real far field stress conditions. In addition, dimensional analyses were performed to correspond the results of lab experiments to field-scale operations. Three different fracturing fluids with viscosities ranging from 20 to 600 Pa.s were used to investigate the effects of varying fracturing fluid viscosities and fluid injection rates on fracturing mechanism. The results indicated that by increasing the fracturing fluid viscosity and fluid injection rates, the fracturing energy rises, and consequently the fracturing pressures will increase. However, as the fracturing energy is transferred to the sample at a faster rate, the fracturing power increases, and accordingly the fracture initiation angle rises; this would lead to more curved fracture planes. It was evident that fractures would reorient perpendicular to the minimum principal stress direction despite the angle of initiation. Furthermore, it was observed that the presence of casing in the wellbore would influence the stress distribution around the casing in such a way that the fracture propagation tends to deviate from the wellbore vicinity.