Affecting analysis of the rheological characteristic and reservoir damage of CO2 fracturing fluid in low permeability shale reservoir

The fracturing property of liquid CO2 fracturing fluid varies greatly due to the rheology of fracturing fluid during fracturing process. The main objective of this investigation is to study the rheology property of thickened liquid CO2 by measuring the viscosity of thickened liquid CO2 in different physical parameters of this prepared thickener and explain the causes of rheological changes. The results show that thickener content, branching content, and molecular weight of a thickener for all could significantly improve the rheology of liquid CO2; the consistency coefficient K increased as they rose, but the rheological index n presented a decreased trend. Meanwhile, the mesh structure is proposed as a model to explain the rheological changes, and the large wetting angle means an excellent backflow, low reservoir damage, and low adsorption property. These results herein provide a basic reference to improve the CO2 fracturing technology and molecular design of CO2 thickener.