纳米变黏滑溜水黏弹携砂机理与渗吸性能.

As a new fracturing fluid system with good sand-carrying performance and imbibition displacement, nano variableviscosity slickwater has been successfully applied to shale oil volume fracturing in Changqing Oilfield. The field test results show that it has good sand-carrying performance and stimulation effect. Under the condition of 40 % sand ratio, the pressure of sand adding process is stable, and the daily oil production of a single well can reach 11.31 tons after fracturing construction, but its sandcarrying mechanism and imbibition performance are not clear. In this paper, the laboratory experimental study on the field concentration of nano variable-viscosity slickwater and the conventional EM30S crosslinkable slickwater system is carried out. Through the experimental methods of dynamic sand-carrying migration, transmission electron microscope (TEM), rheological property evaluation, and pressurized imbibition under the condition of reservoir temperature and pressure, the sand-carrying mechanism of nano variable-viscosity slickwater is revealed and its imbibition performance is evaluated. The experimental results show that the intersection value of elastic modulus and viscous modulus of slickwater reflects the sand-carrying capacity of slickwater solution. The smaller the intersection value is, the stronger the elastic sand-carrying capacity is; Under the same viscosity, the intersection value of viscoelastic modulus of nano variable-viscosity slickwater CNI system is only 0.0741 Hz, which is far lower than 0.181 Hz of field slickwater EM30S, resulting in its static and dynamic elastic sand-carrying performance much higher than EM30S; TEM results show that the strengthening association structure between nano emulsion and variable-viscosity slickwater is the main reason for the enhancement of elastic sand-carrying performance of slickwater. In addition, the results of pressure imbibition experiment show that the nano variable-viscosity slickwater has good imbibition displacement performance, and can replace the crude oil in the nano pores of shale, and the overall recovery can reach 36%. Among them, the order of recovery efficiency of different pore types is: mesopore > micropore > macropore. [ABSTRACT FROM AUTHOR]