Experimental Study on Plugging Behavior of Degradable Diverters in Partially Open Fracture in Temporary Plugging and...

Temporary plugging and diverting fracturing technology (TPDF) has been successfully applied to improve reservoir productivity. In real reservoirs, a considerable number of fractures have relatively rapidly decreasing fracture widths and closed ends. However, the plugging behavior of diverters in this typical fracture called the partially open fracture (POF) is still unclear because of the few related studies. This paper aims to investigate the plugging behavior of diverters at the fracture tip. The 3D-printed fracture model was used to reproduce the partially open fracture, and the morphological characteristics of the partially open fracture and the open fracture were compared based on the scan data. A series of plugging experiments were conducted to monitor the transport behavior of the diverter in partially open fractures through multiple pressure sensors on the fracture model and to investigate the influence of diverter formula and fracture type on plugging behavior. Finally, based on the experimental results, the plugging mechanism of diverters in partially open fractures was analyzed. The plugging experiments show that a higher-pressure distribution appears at the fracture tip when using a combination of fibers and particles, indicating that it is beneficial for the diverter to transport to the tip and form plugging in the fracture, and it should be noted that small changes in particle size and concentration had a significant influence on the plugging performance. Therefore, it is recommended to use a combination of fibers and particles of multiple sizes (maximum particle size not exceeding half of the fracture width) to achieve a better plugging effect. In addition, the plugging behaviors of partially open fractures and open fractures are different. For partially open fractures with widths of 1, 2, and 4 mm, the recommended formula of the diverter is 1 wt % fibers + 1 wt % 0.15 mm particles, 1 wt % fibers + 1 wt % 0.15 mm particles + 1 wt % 1 mm particles, and 1 wt % fibers + 1 wt % 0.15 mm particles + 1 wt % 1 mm particles + 1 wt % 2 mm particles, respectively. The above experimental results provide an experimental and theoretical basis for the application of TPDF in the field.