Reducing the formation of inorganic scales in reuse of shale gas extraction produced-water presents a challenge for desalination systems. The effects of polyethylene glycol modified natural beta-cyclodextrin as an economical and environmentally friendly inhibitor have been investigated by the static experiments, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The experimental results revealed that beta-CD-PEG (polyethylene glycol modified beta-cyclodextrin) achieved the maximum scaling inhibition efficiency of 89.1%, at the 180 mg/L inhibitor, 200 mg/L Ca2+ in the thermostat water bath at 40 degrees C for 6 h. The-results of SEM and XRD studies revealed that both the morphology and aggregation of calcium carbonate crystals had been changed, when the inhibitor was added. Moreover, the TGA further confirmed the scaling mechanism of the copolymer. When the treated water and formation water were mixed together, during the compatibility tests, the mixture was clear. Therefore, the green inhibitor could be applied to prevent the buildup of calcium carbonate for the oilfield flow back water. (C) 2015 Elsevier B.V. All rights reserved.