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

Abstract

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.