A modified Ester-branched thickener for rheology and wettability during CO₂ fracturing for improved fracturing...

The thickening performance of CO₂ fracturing fluid was poor because of the low apparent viscosity. In this paper, the thickening performance of a modified silicone on liquid CO₂ is measured, and a rheology was investigated according to the consistency coefficient K and rheological index n. Meanwhile, a reservoir model was established to evaluate the fracturing property. Results showed that the modified silicone contributes to improve the apparent viscosity of liquid CO₂ and decrease the rheology of liquid CO₂. With the thickener content or pressure increase, the apparent viscosity of liquid CO₂ increases, and the rheological index n decreased obviously. A reduced apparent viscosity is shown as the flow rate or temperature rises, but the rheology increased gradually. The fracturing simulation herein shows that thickened CO₂ fracturing fluid could improve obviously the fracture property. This modified thickener possesses the potential as a thickener and could be a reliable alternative to the thickener in CO₂ fracturing technology, and the large contact angle improved the backflow property of this CO₂ thickener from rock surfaces. The development of CO₂ fracturing technology provides basic data for the improvement of greenhouse effect and clean mining of energy.